test: align test mode with ACK/time flow and expose ack metrics

docs: rewrite README for current multi-meter behavior
Document multi-meter UART mapping and energy-only sender behavior
2026-02-04 20:12:02 +01:00 · 2026-02-04 19:03:43 +01:00 · 2026-02-04 15:22:30 +01:00 · 2026-02-04 15:22:24 +01:00 · 2026-02-04 15:11:07 +01:00 · 2026-02-04 15:10:37 +01:00
36 changed files with 3190 additions and 1406 deletions
--- a/README.md
+++ b/README.md
@@ -1,309 +1,129 @@
-# DD3 LoRa Bridge (Multi-Sender)
+# DD3-LoRa-Bridge-MultiSender

-Unified firmware for LilyGO T3 v1.6.1 (ESP32 + SX1276 + SSD1306) that runs as **Sender** or **Receiver** based on a GPIO jumper. Senders read DD3 smart meter values, compress JSON, and transmit over LoRa. The receiver validates packets, publishes to MQTT, provides a web UI, and shows per-sender status on the OLED.
+Firmware for LilyGO T3 v1.6.1 (`ESP32 + SX1276 + SSD1306`) that runs as either:
+- `Sender` (PIN `GPIO14` HIGH): reads multiple IEC 62056-21 meters, batches data, sends over LoRa.
+- `Receiver` (PIN `GPIO14` LOW): receives/ACKs batches, publishes MQTT, serves web UI, logs to SD.

-## Hardware
-Board: **LilyGO T3 LoRa32 v1.6.1** (ESP32 + SX1276 + SSD1306 128x64 + LiPo)
-Variants:
- SX1276 **433 MHz** module (default build)
- SX1276 **868 MHz** module (use 868 build environments)
+## Current Architecture

-### Pin Mapping
- LoRa (SX1276)
-  - SCK: GPIO5
-  - MISO: GPIO19
-  - MOSI: GPIO27
-  - NSS/CS: GPIO18
-  - RST: GPIO23
-  - DIO0: GPIO26
- OLED (SSD1306)
-  - SDA: GPIO21
-  - SCL: GPIO22
-  - RST: **not used** (SSD1306 init uses `-1` reset pin)
-  - I2C address: 0x3C
- I2C RTC (DS3231)
-  - SDA: GPIO21
-  - SCL: GPIO22
-  - I2C address: 0x68
- Battery ADC: GPIO35 (via on-board divider)
- **Role select**: GPIO13 (INPUT_PULLDOWN)
-  - LOW = Sender
-  - HIGH = Receiver
- **OLED control**: GPIO14 (INPUT_PULLDOWN)
-  - HIGH = force OLED on
-  - LOW = allow auto-off after timeout
- Smart meter UART RX: GPIO34 (input-only, always connected)
+- Single codebase, role selected at boot via `detect_role()` (`include/config.h`, `src/config.cpp`).
+- LoRa link uses explicit CRC16 frame protection in firmware (`src/lora_transport.cpp`), in addition to LoRa PHY CRC.
+- Sender batches up to `30` samples and retransmits on missing ACK (`BATCH_MAX_RETRIES=2`, policy `Keep`).
+- Receiver handles AP fallback when STA config is missing/invalid and exposes a config/status web UI.

-### Notes on GPIOs
- GPIO34/35/36/39 are input-only and have **no internal pullups/pulldowns**.
- Strap pins (GPIO0/2/4/5/12/15) can affect boot; avoid for role or control jumpers.
+## LoRa Frame Protocol (Current)

-## Firmware Roles
-### Sender (battery-powered)
- Reads smart meter via optical IR (UART 9600 7E1).
- Extracts OBIS values:
-  - Energy total: 1-0:1.8.0*255
-  - Total power: 1-0:16.7.0*255
-  - Phase power: 36.7 / 56.7 / 76.7
-  - Phase voltage: 32.7 / 52.7 / 72.7
- Reads battery voltage and estimates SoC.
- Builds JSON payload, compresses, wraps in LoRa packet, transmits.
- Light sleeps between meter reads; batches are sent every 30s.
- Listens for LoRa time sync packets to set UTC clock.
- Uses DS3231 RTC after boot if no time sync has arrived yet.
- OLED shows status + meter data pages.
+Frame format on-air:

-**Sender flow (pseudo-code)**:
-```cpp
-void sender_loop() {
-  meter_read_every_second(); // SML/OBIS -> MeterData samples
-  read_battery(data);        // VBAT + SoC
+`[msg_kind:1][device_short_id:2][payload...][crc16:2]`

-  if (time_to_send_batch()) {
-    json = meterBatchToJson(samples);
-    compressed = compressBuffer(json);
-    lora_send(packet(MeterBatch, compressed));
-  }
+`msg_kind`:
+- `0` = `BatchUp`
+- `1` = `AckDown`

-  display_set_last_meter(data);
-  display_set_last_read(ok);
-  display_set_last_tx(ok);
-  display_tick();
+### `BatchUp`

-  lora_receive_time_sync(); // optional
-  light_sleep_until_next_event();
-}
-```
+`BatchUp` is chunked in transport (`batch_id`, `chunk_index`, `chunk_count`, `total_len`) and then decoded via `payload_codec`.

-**Key sender functions**:
-```cpp
-bool meter_read(MeterData &data);        // parse SML frame, set OBIS fields
-void read_battery(MeterData &data);      // ADC -> volts + percent
-bool meterDataToJson(const MeterData&, String&);
-bool compressBuffer(const uint8_t*, size_t, uint8_t*, size_t, size_t&);
-bool lora_send(const LoraPacket &pkt);   // add header + CRC16 and transmit
-```
+Payload header contains:
+- fixed magic/schema fields (`kMagic=0xDDB3`, `kSchema=2`)
+- `schema_id`
+- sender/batch/time/error metadata

-### Receiver (USB-powered)
- WiFi STA connect using stored config; if not available/fails, starts AP.
- NTP sync (UTC) and local display in Europe/Berlin.
- Receives LoRa packets, verifies CRC16, decompresses, parses JSON.
- Publishes meter JSON to MQTT.
- Web UI:
-  - AP mode: status + WiFi/MQTT config.
-  - STA mode: status + per-sender pages.
- OLED cycles through receiver status and per-sender pages.
+Supported payload schemas in this branch:
+- `schema_id=1` (`EnergyMulti`): integer kWh for up to 3 meters (`energy1_kwh`, `energy2_kwh`, `energy3_kwh`)
+- `schema_id=0` (legacy): older energy/power delta encoding path remains decode-compatible

-**Receiver loop (pseudo-code)**:
-```cpp
-void receiver_loop() {
-  if (lora_receive(pkt)) {
-    if (pkt.type == MeterData) {
-      json = decompressBuffer(pkt.payload);
-      if (jsonToMeterData(json, data)) {
-        update_sender_status(data);
-        mqtt_publish_state(data);
-      }
-    } else if (pkt.type == MeterBatch) {
-      json = reassemble_and_decompress_batch(pkt);
-      for (sample in jsonToMeterBatch(json)) {
-        update_sender_status(sample);
-        mqtt_publish_state(sample);
-      }
-    }
-  }
+`n == 0` is used as sync request (no meter samples).

-  if (time_to_send_timesync()) {
-    time_send_timesync(self_short_id); // 60s for first 10 min, then hourly if RTC is present
-  }
+### `AckDown` (7 bytes)

-  mqtt_loop();
-  web_server_loop();
-  display_set_receiver_status(...);
-  display_tick();
-}
-```
+`[flags:1][batch_id_be:2][epoch_utc_be:4]`

-**Key receiver functions**:
-```cpp
-bool lora_receive(LoraPacket &pkt, uint32_t timeout_ms);
-bool jsonToMeterData(const String &json, MeterData &data);
-bool jsonToMeterBatch(const String &json, MeterData *samples, size_t max, size_t &count);
-bool mqtt_publish_state(const MeterData &data);
-void web_server_loop();                   // AP or STA UI
-void time_send_timesync(uint16_t self_id);
-```
+- `flags bit0`: `time_valid`
+- Receiver sends ACK repeatedly (`ACK_REPEAT_COUNT=3`, `ACK_REPEAT_DELAY_MS=200`).
+- Sender accepts time only if `time_valid=1` and `epoch >= MIN_ACCEPTED_EPOCH_UTC` (`2026-02-01 00:00:00 UTC`).

-## Test Mode (compile-time)
-Enabled by `-DENABLE_TEST_MODE` (see `platformio.ini` test environment).
+## Time Bootstrap Guardrail

- Sender: sends 4-digit test code every ~30s in JSON.
- Receiver: shows last test code per sender and publishes to `/test` topic.
- Normal behavior is excluded from test builds.
+On sender boot:
+- `g_time_acquired=false`
+- only sync requests every `SYNC_REQUEST_INTERVAL_MS` (15s)
+- no normal sampling/transmit until valid ACK time received

-**Test sender (pseudo-code)**:
-```cpp
-void test_sender_loop() {
-  code = random_4_digits();
-  json = {id, role:"sender", test_code: code, ts};
-  lora_send(packet(TestCode, compress(json)));
-  display_set_test_code(code);
-}
-```
+This prevents publishing/storing pre-threshold timestamps.

-**Test receiver (pseudo-code)**:
-```cpp
-void test_receiver_loop() {
-  if (pkt.type == TestCode) {
-    json = decompress(pkt.payload);
-    update_sender_test_code(json);
-    mqtt_publish_test(id, json);
-  }
-}
-```
+## Multi-Meter Sender Behavior

-## LoRa Protocol
-Packet layout:
+Implemented in `src/meter_driver.cpp` + sender path in `src/main.cpp`:

-```
-[0]    protocol_version (1)
-[1]    role (0=sender, 1=receiver)
-[2..3] device_id_short (uint16)
-[4]    payload_type (0=meter, 1=test, 2=time_sync, 3=meter_batch)
-[5..N-3] compressed payload
-[N-2..N-1] CRC16 (bytes 0..N-3)
-```
+- Meter protocol: IEC 62056-21 ASCII, Mode D style framing (`/ ... !`)
+- UART settings: `9600 7E1`
+- Parsed OBIS: `1-0:1.8.0`
+- Conversion: floor to integer kWh (`floorf`)

-LoRa radio settings:
- Frequency: **433 MHz** or **868 MHz** (set by build env via `LORA_FREQUENCY_HZ`)
- SF12, BW 125 kHz, CR 4/5, CRC on, Sync Word 0x34
+Meter count is build-dependent (`include/config.h`):
+- Debug builds (`SERIAL_DEBUG_MODE=1`): `METER_COUNT=2`
+- Prod builds (`SERIAL_DEBUG_MODE=0`): `METER_COUNT=3`

-## Data Format
-JSON payload (sender + MQTT):
+Default RX pins:
+- Meter1: `GPIO34` (`Serial2`)
+- Meter2: `GPIO25` (`Serial1`)
+- Meter3: `GPIO3` (`Serial`, prod only because debug serial is disabled)

-```json
-{
-  "id": "F19C",
-  "ts": 1737200000,
-  "e_kwh": 1234.57,
-  "p_w": 950.00,
-  "p1_w": 500.00,
-  "p2_w": 450.00,
-  "p3_w": 0.00,
-  "v1_v": 230.10,
-  "v2_v": 229.80,
-  "v3_v": 231.00,
-  "bat_v": 3.92,
-  "bat_pct": 78
-}
-```
+## Receiver Behavior

-## Device IDs
- Derived from WiFi STA MAC.
- `short_id = (MAC[4] << 8) | MAC[5]`
- `device_id = dd3-%04X`
- JSON `id` uses only the last 4 hex digits (e.g., `F19C`) to save airtime.
+For valid `BatchUp` decode:
+1. Reassemble chunks and decode payload.
+2. Send `AckDown` immediately.
+3. Drop duplicate batches per sender (`batch_id` tracking).
+4. If `n==0`: treat as sync request only.
+5. Else convert to `MeterData`, log to SD, update web UI, publish MQTT.

-Receiver expects known senders in `include/config.h` via:
-```cpp
-constexpr uint8_t NUM_SENDERS = 1;
-inline constexpr uint16_t EXPECTED_SENDER_IDS[NUM_SENDERS] = { 0xF19C };
-```
+## MQTT Topics and Payloads

-## OLED Behavior
- Sender: OLED stays **ON for 10 seconds** on each wake, then powers down for sleep.
- Receiver: OLED follows the 10-minute auto-off behavior:
-  - GPIO14 HIGH: OLED forced ON.
-  - GPIO14 LOW: auto-off after 10 minutes.
- Pages rotate every 4s.
+State topic:
+- `smartmeter/<device_id>/state`

-## Power & Battery
- Sender disables WiFi/BLE, reads VBAT via ADC, uses linear SoC map:
-  - 3.0 V = 0%
-  - 4.2 V = 100%
- Uses deep sleep between cycles (`SENDER_WAKE_INTERVAL_SEC`).
+Fault topic (retained):
+- `smartmeter/<device_id>/faults`

-## Web UI
- AP SSID: `DD3-Bridge-<short_id>`
- AP password: `changeme123`
- Endpoints:
-  - `/`: status overview
-  - `/wifi`: WiFi/MQTT/NTP config (AP and STA)
-  - `/sender/<device_id>`: per-sender details
+For `EnergyMulti` samples, state JSON includes:
+- `id`, `ts`
+- `energy1_kwh`, `energy2_kwh`, optional `energy3_kwh`
+- `bat_v`, `bat_pct`
+- optional link fields: `rssi`, `snr`
+- fault/reject fields: `err_last`, `rx_reject`, `rx_reject_text` (+ non-zero counters)

-## MQTT
- Topic: `smartmeter/<deviceId>/state`
- QoS 0
- Test mode: `smartmeter/<deviceId>/test`
- Client ID: `dd3-bridge-<device_id>` (stable, derived from MAC)
+Home Assistant discovery publishing is enabled (`ENABLE_HA_DISCOVERY=true`) but still advertises legacy keys (`e_kwh`, `p_w`, `p1_w`, `p2_w`, `p3_w`) in `src/mqtt_client.cpp`.

-## NTP
- NTP servers are configurable in the web UI (`/wifi`).
- Defaults: `pool.ntp.org` and `time.nist.gov`.
-## RTC (DS3231)
- Optional DS3231 on the I2C bus. Connect SDA to GPIO21 and SCL to GPIO22 (same bus as the OLED).
- Enable/disable with `ENABLE_DS3231` in `include/config.h`.
- Receiver time sync packets set the RTC.
- On boot, if no LoRa time sync has arrived yet, the sender uses the RTC time as the initial `ts_utc`.
- When no RTC is present or enabled, the receiver keeps sending time sync every 60 seconds.
+## Web UI, Wi-Fi, Storage
+
+- STA config is stored in Preferences (`wifi_manager`).
+- If STA/MQTT config is unavailable, receiver starts AP mode with SSID prefix `DD3-Bridge-`.
+- Web auth defaults are `admin/admin` (`WEB_AUTH_DEFAULT_USER/PASS`).
+- SD logging is enabled (`ENABLE_SD_LOGGING=true`).

 ## Build Environments
- `lilygo-t3-v1-6-1`: production build
- `lilygo-t3-v1-6-1-test`: test build with `ENABLE_TEST_MODE`
- `lilygo-t3-v1-6-1-868`: production build for 868 MHz modules
- `lilygo-t3-v1-6-1-868-test`: test build for 868 MHz modules

-## Limits & Known Constraints
- **Compression**: uses lightweight RLE (good for JSON but not optimal).
- **OBIS parsing**: supports IEC 62056-21 ASCII (Mode D) and SML; may need tuning for some meters.
- **Payload size**: single JSON frames < 256 bytes (ArduinoJson static doc); batch frames are chunked and reassembled.
- **Battery ADC**: uses simple linear calibration constant in `power_manager.cpp`.
- **OLED**: no hardware reset line is used (matches working reference).
+From `platformio.ini`:

-## Files & Modules
- `include/config.h`, `src/config.cpp`: pins, radio settings, sender IDs
- `include/data_model.h`, `src/data_model.cpp`: MeterData + ID init
- `include/json_codec.h`, `src/json_codec.cpp`: JSON encode/decode
- `include/compressor.h`, `src/compressor.cpp`: RLE compression
- `include/lora_transport.h`, `src/lora_transport.cpp`: LoRa packet + CRC
- `include/meter_driver.h`, `src/meter_driver.cpp`: IEC 62056-21 ASCII + SML parse
- `include/power_manager.h`, `src/power_manager.cpp`: ADC + sleep
- `include/time_manager.h`, `src/time_manager.cpp`: NTP + time sync
- `include/wifi_manager.h`, `src/wifi_manager.cpp`: NVS config + WiFi
- `include/mqtt_client.h`, `src/mqtt_client.cpp`: MQTT publish
- `include/web_server.h`, `src/web_server.cpp`: AP/STA web pages
- `include/display_ui.h`, `src/display_ui.cpp`: OLED pages + control
- `include/test_mode.h`, `src/test_mode.cpp`: test sender/receiver
- `src/main.cpp`: role detection and main loop
+- `lilygo-t3-v1-6-1`
+- `lilygo-t3-v1-6-1-test`
+- `lilygo-t3-v1-6-1-868`
+- `lilygo-t3-v1-6-1-868-test`
+- `lilygo-t3-v1-6-1-payload-test`
+- `lilygo-t3-v1-6-1-868-payload-test`
+- `lilygo-t3-v1-6-1-prod`
+- `lilygo-t3-v1-6-1-868-prod`

-## Quick Start
-1. Set role jumper on GPIO13:
-   - LOW: sender
-   - HIGH: receiver
-2. OLED control on GPIO14:
-   - HIGH: always on
-   - LOW: auto-off after 10 minutes
-3. Build and upload:
+Example:

 ```bash
-pio run -e lilygo-t3-v1-6-1 -t upload --upload-port COMx
+~/.platformio/penv/bin/pio run -e lilygo-t3-v1-6-1
 ```

-Test mode:
-
-```bash
-pio run -e lilygo-t3-v1-6-1-test -t upload --upload-port COMx
-```
-
-868 MHz builds:
-
-```bash
-pio run -e lilygo-t3-v1-6-1-868 -t upload --upload-port COMx
-```
-
-868 MHz test mode:
-
-```bash
-pio run -e lilygo-t3-v1-6-1-868-test -t upload --upload-port COMx
-```
+## Test Mode

+`ENABLE_TEST_MODE` replaces normal sender/receiver loops with dedicated test loops (`src/test_mode.cpp`).
+It sends/receives plain JSON test frames and publishes to `smartmeter/<device_id>/test`.
--- a/include/compressor.h
+++ b/include/compressor.h
@@ -1,6 +0,0 @@
-#pragma once
-
-#include <Arduino.h>
-
-bool compressBuffer(const uint8_t *in, size_t in_len, uint8_t *out, size_t out_max, size_t &out_len);
-bool decompressBuffer(const uint8_t *in, size_t in_len, uint8_t *out, size_t out_max, size_t &out_len);
--- a/include/config.h
+++ b/include/config.h
@@ -7,15 +7,11 @@ enum class DeviceRole : uint8_t {
  Receiver = 1
 };

-enum class PayloadType : uint8_t {
-  MeterData = 0,
-  TestCode = 1,
-  TimeSync = 2,
-  MeterBatch = 3
+enum class BatchRetryPolicy : uint8_t {
+  Keep = 0,
+  Drop = 1
 };

-constexpr uint8_t PROTOCOL_VERSION = 1;
-
 // Pin definitions
 constexpr uint8_t PIN_LORA_SCK = 5;
 constexpr uint8_t PIN_LORA_MISO = 19;
@@ -33,10 +29,12 @@ constexpr uint8_t OLED_HEIGHT = 64;

 constexpr uint8_t PIN_BAT_ADC = 35;

-constexpr uint8_t PIN_ROLE = 13;
-constexpr uint8_t PIN_OLED_CTRL = 14;
+constexpr uint8_t PIN_ROLE = 14;
+constexpr uint8_t PIN_OLED_CTRL = 13;

-constexpr uint8_t PIN_METER_RX = 34;
+constexpr uint8_t PIN_METER1_RX = 34; // UART2 RX
+constexpr uint8_t PIN_METER2_RX = 25; // UART1 RX
+constexpr uint8_t PIN_METER3_RX = 3;  // UART0 RX (prod only, when serial debug is off)

 // LoRa settings
 #ifndef LORA_FREQUENCY_HZ
@@ -47,23 +45,54 @@ constexpr uint8_t LORA_SPREADING_FACTOR = 12;
 constexpr long LORA_BANDWIDTH = 125E3;
 constexpr uint8_t LORA_CODING_RATE = 5;
 constexpr uint8_t LORA_SYNC_WORD = 0x34;
+constexpr uint8_t LORA_PREAMBLE_LEN = 8;

 // Timing
 constexpr uint32_t SENDER_WAKE_INTERVAL_SEC = 30;
-constexpr uint32_t TIME_SYNC_INTERVAL_SEC = 60;
-constexpr uint32_t TIME_SYNC_SLOW_INTERVAL_SEC = 3600;
-constexpr uint32_t TIME_SYNC_FAST_WINDOW_MS = 10UL * 60UL * 1000UL;
-constexpr bool ENABLE_DS3231 = true;
+constexpr uint32_t SYNC_REQUEST_INTERVAL_MS = 15000;
 constexpr uint32_t OLED_PAGE_INTERVAL_MS = 4000;
 constexpr uint32_t OLED_AUTO_OFF_MS = 10UL * 60UL * 1000UL;
 constexpr uint32_t SENDER_OLED_READ_MS = 10000;
 constexpr uint32_t METER_SAMPLE_INTERVAL_MS = 1000;
 constexpr uint32_t METER_SEND_INTERVAL_MS = 30000;
+constexpr uint32_t BATTERY_SAMPLE_INTERVAL_MS = 60000;
+constexpr float BATTERY_CAL = 1.083f;
+constexpr uint32_t BATCH_ACK_TIMEOUT_MS = 3000;
+constexpr uint8_t ACK_REPEAT_COUNT = 3;
+constexpr uint32_t ACK_REPEAT_DELAY_MS = 200;
+constexpr uint8_t BATCH_MAX_RETRIES = 2;
 constexpr uint8_t METER_BATCH_MAX_SAMPLES = 30;
+constexpr uint8_t BATCH_QUEUE_DEPTH = 10;
+constexpr BatchRetryPolicy BATCH_RETRY_POLICY = BatchRetryPolicy::Keep;
 constexpr uint32_t WATCHDOG_TIMEOUT_SEC = 120;
 constexpr bool ENABLE_HA_DISCOVERY = true;
+#ifndef SERIAL_DEBUG_MODE_FLAG
+#define SERIAL_DEBUG_MODE_FLAG 0
+#endif
+constexpr bool SERIAL_DEBUG_MODE = SERIAL_DEBUG_MODE_FLAG != 0;
+constexpr uint8_t METER_COUNT_DEBUG = 2;
+constexpr uint8_t METER_COUNT_PROD = 3;
+constexpr uint8_t METER_COUNT = SERIAL_DEBUG_MODE ? METER_COUNT_DEBUG : METER_COUNT_PROD;
+constexpr bool SERIAL_DEBUG_DUMP_JSON = false;
+constexpr bool LORA_SEND_BYPASS = false;
+constexpr bool ENABLE_SD_LOGGING = true;
+constexpr uint8_t PIN_SD_CS = 13;
+constexpr uint8_t PIN_SD_MOSI = 15;
+constexpr uint8_t PIN_SD_MISO = 2;
+constexpr uint8_t PIN_SD_SCK = 14;
+constexpr uint16_t SD_HISTORY_MAX_DAYS = 30;
+constexpr uint16_t SD_HISTORY_MIN_RES_MIN = 1;
+constexpr uint16_t SD_HISTORY_MAX_BINS = 4000;
+constexpr uint16_t SD_HISTORY_TIME_BUDGET_MS = 10;
+constexpr const char *AP_SSID_PREFIX = "DD3-Bridge-";
+constexpr const char *AP_PASSWORD = "changeme123";
+constexpr bool WEB_AUTH_REQUIRE_STA = true;
+constexpr bool WEB_AUTH_REQUIRE_AP = false;
+constexpr const char *WEB_AUTH_DEFAULT_USER = "admin";
+constexpr const char *WEB_AUTH_DEFAULT_PASS = "admin";

 constexpr uint8_t NUM_SENDERS = 1;
+constexpr uint32_t MIN_ACCEPTED_EPOCH_UTC = 1769904000UL; // 2026-02-01 00:00:00 UTC
 inline constexpr uint16_t EXPECTED_SENDER_IDS[NUM_SENDERS] = {
  0xF19C //433mhz sender
  //0x7EB4 //868mhz sender
--- a/include/data_model.h
+++ b/include/data_model.h
@@ -9,6 +9,15 @@ enum class FaultType : uint8_t {
  LoraTx = 3
 };

+enum class RxRejectReason : uint8_t {
+  None = 0,
+  CrcFail = 1,
+  InvalidMsgKind = 2,
+  LengthMismatch = 3,
+  DeviceIdMismatch = 4,
+  BatchIdMismatch = 5
+};
+
 struct FaultCounters {
  uint32_t meter_read_fail;
  uint32_t decode_fail;
@@ -19,10 +28,12 @@ struct MeterData {
  uint32_t ts_utc;
  uint16_t short_id;
  char device_id[16];
+  bool energy_multi;
+  uint8_t energy_meter_count;
+  uint32_t energy_kwh_int[3];
  float energy_total_kwh;
  float phase_power_w[3];
  float total_power_w;
-  float phase_voltage_v[3];
  float battery_voltage_v;
  uint8_t battery_percent;
  bool valid;
@@ -33,12 +44,15 @@ struct MeterData {
  uint32_t err_decode;
  uint32_t err_lora_tx;
  FaultType last_error;
+  uint8_t rx_reject_reason;
 };

 struct SenderStatus {
  MeterData last_data;
  uint32_t last_update_ts_utc;
+  uint16_t last_acked_batch_id;
  bool has_data;
 };

 void init_device_ids(uint16_t &short_id, char *device_id, size_t device_id_len);
+const char *rx_reject_reason_text(RxRejectReason reason);
--- a/include/display_ui.h
+++ b/include/display_ui.h
@@ -11,6 +11,8 @@ void display_set_sender_statuses(const SenderStatus *statuses, uint8_t count);
 void display_set_last_meter(const MeterData &data);
 void display_set_last_read(bool ok, uint32_t ts_utc);
 void display_set_last_tx(bool ok, uint32_t ts_utc);
+void display_set_sender_queue(uint8_t depth, bool build_pending);
+void display_set_sender_batches(uint16_t last_acked_batch_id, uint16_t current_batch_id);
 void display_set_last_error(FaultType type, uint32_t ts_utc, uint32_t ts_ms);
 void display_set_receiver_status(bool ap_mode, const char *ssid, bool mqtt_ok);
 void display_power_down();
--- a/include/html_util.h
+++ b/include/html_util.h
@@ -0,0 +1,7 @@
+#pragma once
+
+#include <Arduino.h>
+
+String html_escape(const String &input);
+String url_encode_component(const String &input);
+bool sanitize_device_id(const String &input, String &out_device_id);
--- a/include/json_codec.h
+++ b/include/json_codec.h
@@ -4,6 +4,3 @@
 #include "data_model.h"

 bool meterDataToJson(const MeterData &data, String &out_json);
-bool jsonToMeterData(const String &json, MeterData &data);
-bool meterBatchToJson(const MeterData *samples, size_t count, String &out_json, const FaultCounters *faults = nullptr, FaultType last_error = FaultType::None);
-bool jsonToMeterBatch(const String &json, MeterData *out_samples, size_t max_count, size_t &out_count);
--- a/include/lora_transport.h
+++ b/include/lora_transport.h
@@ -2,14 +2,26 @@

 #include <Arduino.h>
 #include "config.h"
+#include "data_model.h"

-constexpr size_t LORA_MAX_PAYLOAD = 200;
+constexpr size_t LORA_MAX_PAYLOAD = 230;
+constexpr size_t LORA_FRAME_HEADER_LEN = 3; // msg_kind + dev_id_short
+constexpr size_t LORA_FRAME_CRC_LEN = 2;
+constexpr size_t LORA_ACK_DOWN_PAYLOAD_LEN = 7; // flags(1) + batch_id(2) + epoch_utc(4)
+static_assert(LORA_ACK_DOWN_PAYLOAD_LEN == 7, "ACK_DOWN payload must remain 7 bytes");
+
+constexpr size_t lora_frame_size(size_t payload_len) {
+  return LORA_FRAME_HEADER_LEN + payload_len + LORA_FRAME_CRC_LEN;
+}
+
+enum class LoraMsgKind : uint8_t {
+  BatchUp = 0,
+  AckDown = 1
+};

 struct LoraPacket {
-  uint8_t protocol_version;
-  DeviceRole role;
+  LoraMsgKind msg_kind;
  uint16_t device_id_short;
-  PayloadType payload_type;
  uint8_t payload[LORA_MAX_PAYLOAD];
  size_t payload_len;
  int16_t rssi_dbm;
@@ -19,4 +31,10 @@ struct LoraPacket {
 void lora_init();
 bool lora_send(const LoraPacket &pkt);
 bool lora_receive(LoraPacket &pkt, uint32_t timeout_ms);
+RxRejectReason lora_get_last_rx_reject_reason();
+bool lora_get_last_rx_signal(int16_t &rssi_dbm, float &snr_db);
+void lora_idle();
 void lora_sleep();
+void lora_receive_continuous();
+bool lora_receive_window(LoraPacket &pkt, uint32_t timeout_ms);
+uint32_t lora_airtime_ms(size_t packet_len);
--- a/include/meter_driver.h
+++ b/include/meter_driver.h
@@ -1,7 +1,8 @@
 #pragma once

 #include <Arduino.h>
-#include "data_model.h"

 void meter_init();
-bool meter_read(MeterData &data);
+void meter_poll();
+uint8_t meter_count();
+bool meter_get_last_energy_kwh(uint8_t meter_idx, uint32_t &out_energy_kwh);
--- a/include/power_manager.h
+++ b/include/power_manager.h
@@ -5,6 +5,7 @@

 void power_sender_init();
 void power_receiver_init();
+void power_configure_unused_pins_sender();
 void read_battery(MeterData &data);
 uint8_t battery_percent_from_voltage(float voltage_v);
 void light_sleep_ms(uint32_t ms);
--- a/include/rtc_ds3231.h
+++ b/include/rtc_ds3231.h
@@ -1,8 +0,0 @@
-#pragma once
-
-#include <Arduino.h>
-
-bool rtc_ds3231_init();
-bool rtc_ds3231_is_present();
-bool rtc_ds3231_read_epoch(uint32_t &epoch_utc);
-bool rtc_ds3231_set_epoch(uint32_t epoch_utc);
--- a/include/time_manager.h
+++ b/include/time_manager.h
@@ -1,17 +1,11 @@
 #pragma once

 #include <Arduino.h>
-#include "lora_transport.h"

 void time_receiver_init(const char *ntp_server_1, const char *ntp_server_2);
 uint32_t time_get_utc();
 bool time_is_synced();
 void time_set_utc(uint32_t epoch);
-bool time_send_timesync(uint16_t device_id_short);
-bool time_handle_timesync_payload(const uint8_t *payload, size_t len);
 void time_get_local_hhmm(char *out, size_t out_len);
-void time_rtc_init();
-bool time_try_load_from_rtc();
-bool time_rtc_present();
 uint32_t time_get_last_sync_utc();
 uint32_t time_get_last_sync_age_sec();
--- a/include/web_server.h
+++ b/include/web_server.h
@@ -7,4 +7,6 @@
 void web_server_begin_ap(const SenderStatus *statuses, uint8_t count);
 void web_server_begin_sta(const SenderStatus *statuses, uint8_t count);
 void web_server_set_config(const WifiMqttConfig &config);
+void web_server_set_sender_faults(const FaultCounters *faults, const FaultType *last_errors);
+void web_server_set_last_batch(uint8_t sender_index, const MeterData *samples, size_t count);
 void web_server_loop();
--- a/include/wifi_manager.h
+++ b/include/wifi_manager.h
@@ -12,6 +12,8 @@ struct WifiMqttConfig {
  String mqtt_pass;
  String ntp_server_1;
  String ntp_server_2;
+  String web_user;
+  String web_pass;
  bool valid;
 };

--- a/platformio.ini
+++ b/platformio.ini
@@ -9,18 +9,7 @@
 ; https://docs.platformio.org/page/projectconf.html

 [env:lilygo-t3-v1-6-1]
-platform = espressif32
-board = ttgo-lora32-v1
-framework = arduino
-lib_deps =
-  sandeepmistry/LoRa@^0.8.0
-  bblanchon/ArduinoJson@^6.21.5
-  adafruit/Adafruit SSD1306@^2.5.9
-  adafruit/Adafruit GFX Library@^1.11.9
-  knolleary/PubSubClient@^2.8
-
-[env:lilygo-t3-v1-6-1-test]
-platform = espressif32
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
 board = ttgo-lora32-v1
 framework = arduino
 lib_deps =
@@ -30,10 +19,24 @@ lib_deps =
  adafruit/Adafruit GFX Library@^1.11.9
  knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
+
+[env:lilygo-t3-v1-6-1-test]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
  -DENABLE_TEST_MODE

 [env:lilygo-t3-v1-6-1-868]
-platform = espressif32
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
 board = ttgo-lora32-v1
 framework = arduino
 lib_deps =
@@ -43,10 +46,11 @@ lib_deps =
  adafruit/Adafruit GFX Library@^1.11.9
  knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
  -DLORA_FREQUENCY_HZ=868E6

 [env:lilygo-t3-v1-6-1-868-test]
-platform = espressif32
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
 board = ttgo-lora32-v1
 framework = arduino
 lib_deps =
@@ -56,5 +60,62 @@ lib_deps =
  adafruit/Adafruit GFX Library@^1.11.9
  knolleary/PubSubClient@^2.8
 build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
  -DENABLE_TEST_MODE
  -DLORA_FREQUENCY_HZ=868E6
+
+[env:lilygo-t3-v1-6-1-payload-test]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
+  -DPAYLOAD_CODEC_TEST
+
+[env:lilygo-t3-v1-6-1-868-payload-test]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=1
+  -DPAYLOAD_CODEC_TEST
+  -DLORA_FREQUENCY_HZ=868E6
+
+[env:lilygo-t3-v1-6-1-prod]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=0
+
+[env:lilygo-t3-v1-6-1-868-prod]
+platform = https://github.com/pioarduino/platform-espressif32/releases/download/51.03.07/platform-espressif32.zip
+board = ttgo-lora32-v1
+framework = arduino
+lib_deps =
+  sandeepmistry/LoRa@^0.8.0
+  bblanchon/ArduinoJson@^6.21.5
+  adafruit/Adafruit SSD1306@^2.5.9
+  adafruit/Adafruit GFX Library@^1.11.9
+  knolleary/PubSubClient@^2.8
+build_flags =
+  -DSERIAL_DEBUG_MODE_FLAG=0
+  -DLORA_FREQUENCY_HZ=868E6
--- a/src/compressor.cpp
+++ b/src/compressor.cpp
@@ -1,71 +0,0 @@
-#include "compressor.h"
-
-static constexpr uint8_t RLE_MARKER = 0xFF;
-
-bool compressBuffer(const uint8_t *in, size_t in_len, uint8_t *out, size_t out_max, size_t &out_len) {
-  out_len = 0;
-  if (!in || !out) {
-    return false;
-  }
-
-  size_t i = 0;
-  while (i < in_len) {
-    uint8_t value = in[i];
-    size_t run = 1;
-    while (i + run < in_len && in[i + run] == value && run < 255) {
-      run++;
-    }
-
-    if (value == RLE_MARKER || run >= 4) {
-      if (out_len + 3 > out_max) {
-        return false;
-      }
-      out[out_len++] = RLE_MARKER;
-      out[out_len++] = static_cast<uint8_t>(run);
-      out[out_len++] = value;
-    } else {
-      if (out_len + run > out_max) {
-        return false;
-      }
-      for (size_t j = 0; j < run; ++j) {
-        out[out_len++] = value;
-      }
-    }
-
-    i += run;
-  }
-
-  return true;
-}
-
-bool decompressBuffer(const uint8_t *in, size_t in_len, uint8_t *out, size_t out_max, size_t &out_len) {
-  out_len = 0;
-  if (!in || !out) {
-    return false;
-  }
-
-  size_t i = 0;
-  while (i < in_len) {
-    uint8_t value = in[i++];
-    if (value == RLE_MARKER) {
-      if (i + 1 >= in_len) {
-        return false;
-      }
-      uint8_t run = in[i++];
-      uint8_t data = in[i++];
-      if (out_len + run > out_max) {
-        return false;
-      }
-      for (uint8_t j = 0; j < run; ++j) {
-        out[out_len++] = data;
-      }
-    } else {
-      if (out_len + 1 > out_max) {
-        return false;
-      }
-      out[out_len++] = value;
-    }
-  }
-
-  return true;
-}
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -2,5 +2,5 @@

 DeviceRole detect_role() {
  pinMode(PIN_ROLE, INPUT_PULLDOWN);
-  return digitalRead(PIN_ROLE) == HIGH ? DeviceRole::Receiver : DeviceRole::Sender;
+  return digitalRead(PIN_ROLE) == HIGH ? DeviceRole::Sender : DeviceRole::Receiver;
 }
--- a/src/data_model.cpp
+++ b/src/data_model.cpp
@@ -8,3 +8,20 @@ void init_device_ids(uint16_t &short_id, char *device_id, size_t device_id_len)
  short_id = (static_cast<uint16_t>(mac[4]) << 8) | mac[5];
  snprintf(device_id, device_id_len, "dd3-%04X", short_id);
 }
+
+const char *rx_reject_reason_text(RxRejectReason reason) {
+  switch (reason) {
+    case RxRejectReason::CrcFail:
+      return "crc_fail";
+    case RxRejectReason::InvalidMsgKind:
+      return "invalid_msg_kind";
+    case RxRejectReason::LengthMismatch:
+      return "length_mismatch";
+    case RxRejectReason::DeviceIdMismatch:
+      return "device_id_mismatch";
+    case RxRejectReason::BatchIdMismatch:
+      return "batch_id_mismatch";
+    default:
+      return "none";
+  }
+}
--- a/src/display_ui.cpp
+++ b/src/display_ui.cpp
@@ -4,6 +4,8 @@
 #include <Wire.h>
 #include <Adafruit_GFX.h>
 #include <Adafruit_SSD1306.h>
+#include <limits.h>
+#include <math.h>
 #include <time.h>

 static Adafruit_SSD1306 display(OLED_WIDTH, OLED_HEIGHT, &Wire, -1);
@@ -19,6 +21,10 @@ static uint32_t g_last_read_ts = 0;
 static uint32_t g_last_tx_ts = 0;
 static uint32_t g_last_read_ms = 0;
 static uint32_t g_last_tx_ms = 0;
+static uint8_t g_sender_queue_depth = 0;
+static bool g_sender_build_pending = false;
+static uint16_t g_sender_last_acked_batch_id = 0;
+static uint16_t g_sender_current_batch_id = 0;
 static FaultType g_last_error = FaultType::None;
 static uint32_t g_last_error_ts = 0;
 static uint32_t g_last_error_ms = 0;
@@ -32,10 +38,9 @@ static bool g_mqtt_ok = false;

 static bool g_oled_on = true;
 static bool g_prev_ctrl_high = false;
-static uint32_t g_oled_off_start = 0;
 static uint32_t g_last_page_ms = 0;
 static uint8_t g_page = 0;
-static uint32_t g_boot_ms = 0;
+static uint32_t g_last_activity_ms = 0;
 static bool g_display_ready = false;
 static uint32_t g_last_init_attempt_ms = 0;
 static bool g_last_oled_on = true;
@@ -65,7 +70,9 @@ void display_power_down() {
 }

 void display_init() {
+  if (g_role == DeviceRole::Sender) {
    pinMode(PIN_OLED_CTRL, INPUT_PULLDOWN);
+  }
  Wire.begin(PIN_OLED_SDA, PIN_OLED_SCL);
  Wire.setClock(100000);
  g_display_ready = display.begin(SSD1306_SWITCHCAPVCC, OLED_I2C_ADDR);
@@ -77,7 +84,7 @@ void display_init() {
    display.display();
  }
  g_last_init_attempt_ms = millis();
-  g_boot_ms = millis();
+  g_last_activity_ms = millis();
 }

 void display_set_role(DeviceRole role) {
@@ -111,6 +118,16 @@ void display_set_last_tx(bool ok, uint32_t ts_utc) {
  g_last_tx_ms = millis();
 }

+void display_set_sender_queue(uint8_t depth, bool build_pending) {
+  g_sender_queue_depth = depth;
+  g_sender_build_pending = build_pending;
+}
+
+void display_set_sender_batches(uint16_t last_acked_batch_id, uint16_t current_batch_id) {
+  g_sender_last_acked_batch_id = last_acked_batch_id;
+  g_sender_current_batch_id = current_batch_id;
+}
+
 void display_set_last_error(FaultType type, uint32_t ts_utc, uint32_t ts_ms) {
  g_last_error = type;
  g_last_error_ts = ts_utc;
@@ -146,6 +163,20 @@ static uint32_t age_seconds(uint32_t ts_utc, uint32_t ts_ms) {
  return (millis() - ts_ms) / 1000;
 }

+static int32_t round_power_w(float value) {
+  if (isnan(value)) {
+    return 0;
+  }
+  long rounded = lroundf(value);
+  if (rounded > INT32_MAX) {
+    return INT32_MAX;
+  }
+  if (rounded < INT32_MIN) {
+    return INT32_MIN;
+  }
+  return static_cast<int32_t>(rounded);
+}
+
 static bool render_last_error_line(uint8_t y) {
  if (g_last_error == FaultType::None) {
    return false;
@@ -195,7 +226,13 @@ static void render_sender_status() {
  display.printf("Read %s %lus ago", g_last_read_ok ? "OK" : "ERR", static_cast<unsigned long>(age_seconds(g_last_read_ts, g_last_read_ms)));

  display.setCursor(0, 36);
-  display.printf("TX %s %lus ago", g_last_tx_ok ? "OK" : "ERR", static_cast<unsigned long>(age_seconds(g_last_tx_ts, g_last_tx_ms)));
+  display.printf("TX %s %lus Q%u%s A%u C%u",
+                 g_last_tx_ok ? "OK" : "ERR",
+                 static_cast<unsigned long>(age_seconds(g_last_tx_ts, g_last_tx_ms)),
+                 g_sender_queue_depth,
+                 g_sender_build_pending ? "+" : "",
+                 g_sender_last_acked_batch_id,
+                 g_sender_current_batch_id);

 #ifdef ENABLE_TEST_MODE
  if (strlen(g_test_code) > 0) {
@@ -215,15 +252,15 @@ static void render_sender_status() {
 static void render_sender_measurement() {
  display.clearDisplay();
  display.setCursor(0, 0);
-  display.printf("E %.1f kWh", g_last_meter.energy_total_kwh);
+  display.printf("E %.2f kWh", g_last_meter.energy_total_kwh);
  display.setCursor(0, 12);
-  display.printf("P %.0fW", g_last_meter.total_power_w);
+  display.printf("P %dW", static_cast<int>(round_power_w(g_last_meter.total_power_w)));
  display.setCursor(0, 24);
-  display.printf("L1 %.0fV %.0fW", g_last_meter.phase_voltage_v[0], g_last_meter.phase_power_w[0]);
+  display.printf("L1 %dW", static_cast<int>(round_power_w(g_last_meter.phase_power_w[0])));
  display.setCursor(0, 36);
-  display.printf("L2 %.0fV %.0fW", g_last_meter.phase_voltage_v[1], g_last_meter.phase_power_w[1]);
+  display.printf("L2 %dW", static_cast<int>(round_power_w(g_last_meter.phase_power_w[1])));
  display.setCursor(0, 48);
-  display.printf("L3 %.0fV %.0fW", g_last_meter.phase_voltage_v[2], g_last_meter.phase_power_w[2]);
+  display.printf("L3 %dW", static_cast<int>(round_power_w(g_last_meter.phase_power_w[2])));
  display.display();
 }

@@ -248,16 +285,10 @@ static void render_receiver_status() {
  display.printf("Time: %s", time_buf);

  uint32_t latest = 0;
-  bool link_valid = false;
-  int16_t link_rssi = 0;
-  float link_snr = 0.0f;
  if (g_statuses) {
    for (uint8_t i = 0; i < g_status_count; ++i) {
      if (g_statuses[i].has_data && g_statuses[i].last_update_ts_utc > latest) {
        latest = g_statuses[i].last_update_ts_utc;
-        link_valid = g_statuses[i].last_data.link_valid;
-        link_rssi = g_statuses[i].last_data.link_rssi_dbm;
-        link_snr = g_statuses[i].last_data.link_snr_db;
      }
    }
  }
@@ -271,9 +302,6 @@ static void render_receiver_status() {
    localtime_r(&t, &timeinfo);
    display.printf("Upd %02d:%02d", timeinfo.tm_hour, timeinfo.tm_min);
  }
-  if (link_valid) {
-    display.printf(" R:%d S:%.1f", link_rssi, link_snr);
-  }

  render_last_error_line(56);
  display.display();
@@ -292,7 +320,15 @@ static void render_receiver_sender(uint8_t index) {
  display.setCursor(0, 0);
  uint8_t bat = status.has_data ? status.last_data.battery_percent : 0;
  if (status.has_data) {
-    display.printf("%s B%u", status.last_data.device_id, bat);
+    const char *device_id = status.last_data.device_id;
+    if (strlen(device_id) >= 4 && strncmp(device_id, "dd3-", 4) == 0) {
+      device_id += 4;
+    }
+    if (status.last_data.link_valid) {
+      display.printf("%s R:%d S:%.1f", device_id, status.last_data.link_rssi_dbm, status.last_data.link_snr_db);
+    } else {
+      display.printf("%s B%u", device_id, bat);
+    }
  } else {
    display.printf("%s B--", status.last_data.device_id);
  }
@@ -314,19 +350,37 @@ static void render_receiver_sender(uint8_t index) {
 #endif

  display.setCursor(0, 12);
-  display.printf("E %.1f kWh", status.last_data.energy_total_kwh);
-  display.setCursor(0, 24);
-  display.printf("P %.0fW", status.last_data.total_power_w);
-  display.setCursor(0, 36);
-  display.printf("L1 %.0fV %.0fW", status.last_data.phase_voltage_v[0], status.last_data.phase_power_w[0]);
-  display.setCursor(0, 48);
-  display.printf("L2 %.0fV %.0fW", status.last_data.phase_voltage_v[1], status.last_data.phase_power_w[1]);
-  display.setCursor(0, 56);
-  if (status.last_data.link_valid) {
-    display.printf("R:%d S:%.1f", status.last_data.link_rssi_dbm, status.last_data.link_snr_db);
+  if (status.last_data.energy_multi) {
+    display.printf("E1 %lu E2 %lu", static_cast<unsigned long>(status.last_data.energy_kwh_int[0]),
+                   static_cast<unsigned long>(status.last_data.energy_kwh_int[1]));
  } else {
-    display.printf("L3 %.0fV %.0fW", status.last_data.phase_voltage_v[2], status.last_data.phase_power_w[2]);
+    display.printf("E %.2f kWh", status.last_data.energy_total_kwh);
  }
+  display.setCursor(0, 22);
+  if (status.last_data.energy_multi && status.last_data.energy_meter_count >= 3) {
+    display.printf("E3 %lu", static_cast<unsigned long>(status.last_data.energy_kwh_int[2]));
+  } else {
+    display.printf("L1 %dW", static_cast<int>(round_power_w(status.last_data.phase_power_w[0])));
+  }
+  display.setCursor(0, 32);
+  display.printf("L2 %dW", static_cast<int>(round_power_w(status.last_data.phase_power_w[1])));
+  display.setCursor(0, 42);
+  display.printf("L3 %dW", static_cast<int>(round_power_w(status.last_data.phase_power_w[2])));
+  display.setCursor(0, 52);
+  display.print("P");
+  char p_buf[16];
+  snprintf(p_buf, sizeof(p_buf), "%dW", static_cast<int>(round_power_w(status.last_data.total_power_w)));
+  int16_t x1 = 0;
+  int16_t y1 = 0;
+  uint16_t w = 0;
+  uint16_t h = 0;
+  display.getTextBounds(p_buf, 0, 0, &x1, &y1, &w, &h);
+  int16_t x = static_cast<int16_t>(display.width() - w);
+  if (x < 0) {
+    x = 0;
+  }
+  display.setCursor(x, 52);
+  display.print(p_buf);
  display.display();
 }

@@ -345,26 +399,21 @@ void display_tick() {
    }
    return;
  }
-  bool ctrl_high = digitalRead(PIN_OLED_CTRL) == HIGH;
+  bool ctrl_high = false;
+  if (g_role == DeviceRole::Sender) {
+    ctrl_high = digitalRead(PIN_OLED_CTRL) == HIGH;
+  }

-  bool in_boot_window = (millis() - g_boot_ms) < OLED_AUTO_OFF_MS;
-  if (in_boot_window) {
+  uint32_t now_ms = millis();
+  bool ctrl_falling_edge = g_prev_ctrl_high && !ctrl_high;
+  if (g_role == DeviceRole::Receiver) {
    g_oled_on = true;
+    g_last_activity_ms = now_ms;
  } else {
-    if (ctrl_high) {
-      g_oled_on = true;
-      g_oled_off_start = 0;
-    } else if (g_prev_ctrl_high && !ctrl_high) {
-      g_oled_off_start = millis();
-    } else if (!g_prev_ctrl_high && !ctrl_high && g_oled_off_start == 0) {
-      g_oled_off_start = millis();
+    if (ctrl_high || ctrl_falling_edge) {
+      g_last_activity_ms = now_ms;
    }
-
-    if (!ctrl_high && g_oled_off_start > 0 && millis() - g_oled_off_start > OLED_AUTO_OFF_MS) {
-      g_oled_on = false;
-    }
-
-    // fall through to power gating below
+    g_oled_on = (now_ms - g_last_activity_ms) < OLED_AUTO_OFF_MS;
  }

  if (g_oled_on) {
--- a/src/html_util.cpp
+++ b/src/html_util.cpp
@@ -0,0 +1,98 @@
+#include "html_util.h"
+
+String html_escape(const String &input) {
+  String out;
+  out.reserve(input.length() + 8);
+  for (size_t i = 0; i < input.length(); ++i) {
+    char c = input[i];
+    switch (c) {
+      case '&':
+        out += "&amp;";
+        break;
+      case '<':
+        out += "&lt;";
+        break;
+      case '>':
+        out += "&gt;";
+        break;
+      case '"':
+        out += "&quot;";
+        break;
+      case '\'':
+        out += "&#39;";
+        break;
+      default:
+        out += c;
+        break;
+    }
+  }
+  return out;
+}
+
+String url_encode_component(const String &input) {
+  String out;
+  out.reserve(input.length() * 3);
+  const char *hex = "0123456789ABCDEF";
+  for (size_t i = 0; i < input.length(); ++i) {
+    unsigned char c = static_cast<unsigned char>(input[i]);
+    bool safe = (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') ||
+        (c >= '0' && c <= '9') || c == '-' || c == '_' || c == '.' || c == '~';
+    if (safe) {
+      out += static_cast<char>(c);
+    } else {
+      out += '%';
+      out += hex[(c >> 4) & 0x0F];
+      out += hex[c & 0x0F];
+    }
+  }
+  return out;
+}
+
+static bool is_hex_char(char c) {
+  return (c >= '0' && c <= '9') ||
+      (c >= 'a' && c <= 'f') ||
+      (c >= 'A' && c <= 'F');
+}
+
+static String to_upper_hex4(const String &input) {
+  String out = input;
+  out.toUpperCase();
+  return out;
+}
+
+bool sanitize_device_id(const String &input, String &out_device_id) {
+  String trimmed = input;
+  trimmed.trim();
+  if (trimmed.length() == 0) {
+    return false;
+  }
+  if (trimmed.indexOf('/') >= 0 || trimmed.indexOf('\\') >= 0 || trimmed.indexOf("..") >= 0) {
+    return false;
+  }
+  if (trimmed.indexOf('%') >= 0) {
+    return false;
+  }
+
+  if (trimmed.length() == 4) {
+    for (size_t i = 0; i < 4; ++i) {
+      if (!is_hex_char(trimmed[i])) {
+        return false;
+      }
+    }
+    out_device_id = String("dd3-") + to_upper_hex4(trimmed);
+    return true;
+  }
+
+  if (trimmed.length() == 8 && trimmed.startsWith("dd3-")) {
+    String hex = trimmed.substring(4);
+    for (size_t i = 0; i < 4; ++i) {
+      if (!is_hex_char(hex[i])) {
+        return false;
+      }
+    }
+    out_device_id = String("dd3-") + to_upper_hex4(hex);
+    return true;
+  }
+
+  return false;
+}
--- a/src/json_codec.cpp
+++ b/src/json_codec.cpp
@@ -1,7 +1,7 @@
 #include "json_codec.h"
 #include <ArduinoJson.h>
+#include <limits.h>
 #include <math.h>
-#include "power_manager.h"

 static float round2(float value) {
  if (isnan(value)) {
@@ -10,6 +10,20 @@ static float round2(float value) {
  return roundf(value * 100.0f) / 100.0f;
 }

+static int32_t round_to_i32(float value) {
+  if (isnan(value)) {
+    return 0;
+  }
+  long rounded = lroundf(value);
+  if (rounded > INT32_MAX) {
+    return INT32_MAX;
+  }
+  if (rounded < INT32_MIN) {
+    return INT32_MIN;
+  }
+  return static_cast<int32_t>(rounded);
+}
+
 static const char *short_id_from_device_id(const char *device_id) {
  if (!device_id) {
    return "";
@@ -32,27 +46,36 @@ static void format_float_2(char *buf, size_t buf_len, float value) {
  snprintf(buf, buf_len, "%.2f", round2(value));
 }

+static void set_int_or_null(JsonDocument &doc, const char *key, float value) {
+  if (!key || key[0] == '\0') {
+    return;
+  }
+  if (isnan(value)) {
+    doc[key] = nullptr;
+    return;
+  }
+  doc[key] = round_to_i32(value);
+}
+
 bool meterDataToJson(const MeterData &data, String &out_json) {
-  StaticJsonDocument<256> doc;
+  StaticJsonDocument<320> doc;
  doc["id"] = short_id_from_device_id(data.device_id);
  doc["ts"] = data.ts_utc;
  char buf[16];
+  if (data.energy_multi) {
+    doc["energy1_kwh"] = data.energy_kwh_int[0];
+    doc["energy2_kwh"] = data.energy_kwh_int[1];
+    if (data.energy_meter_count >= 3) {
+      doc["energy3_kwh"] = data.energy_kwh_int[2];
+    }
+  } else {
    format_float_2(buf, sizeof(buf), data.energy_total_kwh);
    doc["e_kwh"] = serialized(buf);
-  format_float_2(buf, sizeof(buf), data.total_power_w);
-  doc["p_w"] = serialized(buf);
-  format_float_2(buf, sizeof(buf), data.phase_power_w[0]);
-  doc["p1_w"] = serialized(buf);
-  format_float_2(buf, sizeof(buf), data.phase_power_w[1]);
-  doc["p2_w"] = serialized(buf);
-  format_float_2(buf, sizeof(buf), data.phase_power_w[2]);
-  doc["p3_w"] = serialized(buf);
-  format_float_2(buf, sizeof(buf), data.phase_voltage_v[0]);
-  doc["v1_v"] = serialized(buf);
-  format_float_2(buf, sizeof(buf), data.phase_voltage_v[1]);
-  doc["v2_v"] = serialized(buf);
-  format_float_2(buf, sizeof(buf), data.phase_voltage_v[2]);
-  doc["v3_v"] = serialized(buf);
+    set_int_or_null(doc, "p_w", data.total_power_w);
+    set_int_or_null(doc, "p1_w", data.phase_power_w[0]);
+    set_int_or_null(doc, "p2_w", data.phase_power_w[1]);
+    set_int_or_null(doc, "p3_w", data.phase_power_w[2]);
+  }
  format_float_2(buf, sizeof(buf), data.battery_voltage_v);
  doc["bat_v"] = serialized(buf);
  doc["bat_pct"] = data.battery_percent;
@@ -69,177 +92,11 @@ bool meterDataToJson(const MeterData &data, String &out_json) {
  if (data.err_lora_tx > 0) {
    doc["err_tx"] = data.err_lora_tx;
  }
-  if (data.last_error != FaultType::None) {
  doc["err_last"] = static_cast<uint8_t>(data.last_error);
-  }
+  doc["rx_reject"] = data.rx_reject_reason;
+  doc["rx_reject_text"] = rx_reject_reason_text(static_cast<RxRejectReason>(data.rx_reject_reason));

  out_json = "";
  size_t len = serializeJson(doc, out_json);
-  return len > 0 && len < 256;
-}
-
-static float read_float_or_legacy(JsonDocument &doc, const char *key, const char *legacy_key) {
-  if (doc[key].isNull()) {
-    return doc[legacy_key] | NAN;
-  }
-  return doc[key] | NAN;
-}
-
-bool jsonToMeterData(const String &json, MeterData &data) {
-  StaticJsonDocument<256> doc;
-  DeserializationError err = deserializeJson(doc, json);
-  if (err) {
-    return false;
-  }
-
-  const char *id = doc["id"] | "";
-  if (strlen(id) == 4) {
-    snprintf(data.device_id, sizeof(data.device_id), "dd3-%s", id);
-  } else {
-    strncpy(data.device_id, id, sizeof(data.device_id));
-  }
-  data.device_id[sizeof(data.device_id) - 1] = '\0';
-
-  data.ts_utc = doc["ts"] | 0;
-  data.energy_total_kwh = read_float_or_legacy(doc, "e_kwh", "energy_kwh");
-  data.total_power_w = read_float_or_legacy(doc, "p_w", "p_total_w");
-  data.phase_power_w[0] = doc["p1_w"] | NAN;
-  data.phase_power_w[1] = doc["p2_w"] | NAN;
-  data.phase_power_w[2] = doc["p3_w"] | NAN;
-  data.phase_voltage_v[0] = doc["v1_v"] | NAN;
-  data.phase_voltage_v[1] = doc["v2_v"] | NAN;
-  data.phase_voltage_v[2] = doc["v3_v"] | NAN;
-  data.battery_voltage_v = doc["bat_v"] | NAN;
-  if (doc["bat_pct"].isNull() && !isnan(data.battery_voltage_v)) {
-    data.battery_percent = battery_percent_from_voltage(data.battery_voltage_v);
-  } else {
-    data.battery_percent = doc["bat_pct"] | 0;
-  }
-  data.valid = true;
-  data.link_valid = false;
-  data.link_rssi_dbm = 0;
-  data.link_snr_db = NAN;
-  data.err_meter_read = doc["err_m"] | 0;
-  data.err_decode = doc["err_d"] | 0;
-  data.err_lora_tx = doc["err_tx"] | 0;
-  data.last_error = static_cast<FaultType>(doc["err_last"] | 0);
-
-  if (strlen(data.device_id) >= 8) {
-    const char *suffix = data.device_id + strlen(data.device_id) - 4;
-    data.short_id = static_cast<uint16_t>(strtoul(suffix, nullptr, 16));
-  }
-
-  return true;
-}
-
-bool meterBatchToJson(const MeterData *samples, size_t count, String &out_json, const FaultCounters *faults, FaultType last_error) {
-  if (!samples || count == 0) {
-    return false;
-  }
-
-  DynamicJsonDocument doc(8192);
-  doc["id"] = short_id_from_device_id(samples[count - 1].device_id);
-  doc["bat_v"] = round2(samples[count - 1].battery_voltage_v);
-  doc["bat_pct"] = samples[count - 1].battery_percent;
-  if (faults) {
-    if (faults->meter_read_fail > 0) {
-      doc["err_m"] = faults->meter_read_fail;
-    }
-    if (faults->lora_tx_fail > 0) {
-      doc["err_tx"] = faults->lora_tx_fail;
-    }
-  }
-  if (last_error != FaultType::None) {
-    doc["err_last"] = static_cast<uint8_t>(last_error);
-  }
-  JsonArray arr = doc.createNestedArray("s");
-  for (size_t i = 0; i < count; ++i) {
-    JsonArray row = arr.createNestedArray();
-    row.add(samples[i].ts_utc);
-    row.add(round2(samples[i].energy_total_kwh));
-    row.add(round2(samples[i].total_power_w));
-    row.add(round2(samples[i].phase_power_w[0]));
-    row.add(round2(samples[i].phase_power_w[1]));
-    row.add(round2(samples[i].phase_power_w[2]));
-    row.add(round2(samples[i].phase_voltage_v[0]));
-    row.add(round2(samples[i].phase_voltage_v[1]));
-    row.add(round2(samples[i].phase_voltage_v[2]));
-    row.add(samples[i].valid ? 1 : 0);
-  }
-
-  out_json = "";
-  size_t len = serializeJson(doc, out_json);
-  return len > 0;
-}
-
-bool jsonToMeterBatch(const String &json, MeterData *out_samples, size_t max_count, size_t &out_count) {
-  out_count = 0;
-  if (!out_samples || max_count == 0) {
-    return false;
-  }
-
-  DynamicJsonDocument doc(8192);
-  DeserializationError err = deserializeJson(doc, json);
-  if (err) {
-    return false;
-  }
-
-  JsonArray arr = doc["s"].as<JsonArray>();
-  if (arr.isNull()) {
-    return false;
-  }
-
-  const char *id = doc["id"] | "";
-  float bat_v = doc["bat_v"] | NAN;
-  uint8_t bat_pct = doc["bat_pct"] | 0;
-  uint32_t err_m = doc["err_m"] | 0;
-  uint32_t err_tx = doc["err_tx"] | 0;
-  FaultType last_error = static_cast<FaultType>(doc["err_last"] | 0);
-
-  size_t idx = 0;
-  for (JsonArray row : arr) {
-    if (idx >= max_count) {
-      break;
-    }
-    MeterData &data = out_samples[idx];
-    data = {};
-    if (strlen(id) == 4) {
-      snprintf(data.device_id, sizeof(data.device_id), "dd3-%s", id);
-    } else {
-      strncpy(data.device_id, id, sizeof(data.device_id));
-    }
-    data.device_id[sizeof(data.device_id) - 1] = '\0';
-    data.ts_utc = row[0] | 0;
-    data.energy_total_kwh = row[1] | NAN;
-    data.total_power_w = row[2] | NAN;
-    data.phase_power_w[0] = row[3] | NAN;
-    data.phase_power_w[1] = row[4] | NAN;
-    data.phase_power_w[2] = row[5] | NAN;
-    data.phase_voltage_v[0] = row[6] | NAN;
-    data.phase_voltage_v[1] = row[7] | NAN;
-    data.phase_voltage_v[2] = row[8] | NAN;
-    data.valid = (row[9] | 1) != 0;
-    data.battery_voltage_v = bat_v;
-    if (doc["bat_pct"].isNull() && !isnan(bat_v)) {
-      data.battery_percent = battery_percent_from_voltage(bat_v);
-    } else {
-      data.battery_percent = bat_pct;
-    }
-    data.link_valid = false;
-    data.link_rssi_dbm = 0;
-    data.link_snr_db = NAN;
-    data.err_meter_read = err_m;
-    data.err_decode = 0;
-    data.err_lora_tx = err_tx;
-    data.last_error = last_error;
-
-    if (strlen(data.device_id) >= 8) {
-      const char *suffix = data.device_id + strlen(data.device_id) - 4;
-      data.short_id = static_cast<uint16_t>(strtoul(suffix, nullptr, 16));
-    }
-    idx++;
-  }
-
-  out_count = idx;
-  return idx > 0;
+  return len > 0 && len < 320;
 }
--- a/src/lora_transport.cpp
+++ b/src/lora_transport.cpp
@@ -1,6 +1,39 @@
 #include "lora_transport.h"
 #include <LoRa.h>
 #include <SPI.h>
+#include <math.h>
+
+static RxRejectReason g_last_rx_reject_reason = RxRejectReason::None;
+static uint32_t g_last_rx_reject_log_ms = 0;
+static bool g_last_rx_signal_valid = false;
+static int16_t g_last_rx_rssi_dbm = 0;
+static float g_last_rx_snr_db = 0.0f;
+
+static void note_reject(RxRejectReason reason) {
+  g_last_rx_reject_reason = reason;
+  if (SERIAL_DEBUG_MODE) {
+    uint32_t now_ms = millis();
+    if (now_ms - g_last_rx_reject_log_ms >= 1000) {
+      g_last_rx_reject_log_ms = now_ms;
+      Serial.printf("lora_rx: reject reason=%s\n", rx_reject_reason_text(reason));
+    }
+  }
+}
+
+RxRejectReason lora_get_last_rx_reject_reason() {
+  RxRejectReason reason = g_last_rx_reject_reason;
+  g_last_rx_reject_reason = RxRejectReason::None;
+  return reason;
+}
+
+bool lora_get_last_rx_signal(int16_t &rssi_dbm, float &snr_db) {
+  if (!g_last_rx_signal_valid) {
+    return false;
+  }
+  rssi_dbm = g_last_rx_rssi_dbm;
+  snr_db = g_last_rx_snr_db;
+  return true;
+}

 static uint16_t crc16_ccitt(const uint8_t *data, size_t len) {
  uint16_t crc = 0xFFFF;
@@ -29,13 +62,26 @@ void lora_init() {
 }

 bool lora_send(const LoraPacket &pkt) {
-  uint8_t buffer[5 + LORA_MAX_PAYLOAD + 2];
+  if (LORA_SEND_BYPASS) {
+    return true;
+  }
+  uint32_t t0 = 0;
+  uint32_t t1 = 0;
+  uint32_t t2 = 0;
+  uint32_t t3 = 0;
+  uint32_t t4 = 0;
+  if (SERIAL_DEBUG_MODE) {
+    t0 = millis();
+  }
+  LoRa.idle();
+  if (SERIAL_DEBUG_MODE) {
+    t1 = millis();
+  }
+  uint8_t buffer[1 + 2 + LORA_MAX_PAYLOAD + 2];
  size_t idx = 0;
-  buffer[idx++] = pkt.protocol_version;
-  buffer[idx++] = static_cast<uint8_t>(pkt.role);
+  buffer[idx++] = static_cast<uint8_t>(pkt.msg_kind);
  buffer[idx++] = static_cast<uint8_t>(pkt.device_id_short >> 8);
  buffer[idx++] = static_cast<uint8_t>(pkt.device_id_short & 0xFF);
-  buffer[idx++] = static_cast<uint8_t>(pkt.payload_type);

  if (pkt.payload_len > LORA_MAX_PAYLOAD) {
    return false;
@@ -49,8 +95,24 @@ bool lora_send(const LoraPacket &pkt) {
  buffer[idx++] = static_cast<uint8_t>(crc & 0xFF);

  LoRa.beginPacket();
+  if (SERIAL_DEBUG_MODE) {
+    t2 = millis();
+  }
  LoRa.write(buffer, idx);
-  int result = LoRa.endPacket();
+  if (SERIAL_DEBUG_MODE) {
+    t3 = millis();
+  }
+  int result = LoRa.endPacket(false);
+  if (SERIAL_DEBUG_MODE) {
+    t4 = millis();
+    Serial.printf("lora_tx: idle=%lums begin=%lums write=%lums end=%lums total=%lums len=%u\n",
+                  static_cast<unsigned long>(t1 - t0),
+                  static_cast<unsigned long>(t2 - t1),
+                  static_cast<unsigned long>(t3 - t2),
+                  static_cast<unsigned long>(t4 - t3),
+                  static_cast<unsigned long>(t4 - t0),
+                  static_cast<unsigned>(idx));
+  }
  return result == 1;
 }

@@ -59,40 +121,61 @@ bool lora_receive(LoraPacket &pkt, uint32_t timeout_ms) {
  while (true) {
    int packet_size = LoRa.parsePacket();
    if (packet_size > 0) {
-      if (packet_size < 7) {
+      g_last_rx_rssi_dbm = static_cast<int16_t>(LoRa.packetRssi());
+      g_last_rx_snr_db = LoRa.packetSnr();
+      g_last_rx_signal_valid = true;
+
+      if (packet_size < 5) {
        while (LoRa.available()) {
          LoRa.read();
        }
+        note_reject(RxRejectReason::LengthMismatch);
        return false;
      }

-      uint8_t buffer[5 + LORA_MAX_PAYLOAD + 2];
+      uint8_t buffer[1 + 2 + LORA_MAX_PAYLOAD + 2];
      size_t len = 0;
      while (LoRa.available() && len < sizeof(buffer)) {
        buffer[len++] = LoRa.read();
      }
+      if (LoRa.available()) {
+        while (LoRa.available()) {
+          LoRa.read();
+        }
+        if (SERIAL_DEBUG_MODE) {
+          Serial.println("rx_reject: oversize packet drained");
+        }
+        note_reject(RxRejectReason::LengthMismatch);
+        return false;
+      }

-      if (len < 7) {
+      if (len < 5) {
+        note_reject(RxRejectReason::LengthMismatch);
        return false;
      }

      uint16_t crc_calc = crc16_ccitt(buffer, len - 2);
      uint16_t crc_rx = static_cast<uint16_t>(buffer[len - 2] << 8) | buffer[len - 1];
      if (crc_calc != crc_rx) {
+        note_reject(RxRejectReason::CrcFail);
+        return false;
+      }
+      uint8_t msg_kind = buffer[0];
+      if (msg_kind > static_cast<uint8_t>(LoraMsgKind::AckDown)) {
+        note_reject(RxRejectReason::InvalidMsgKind);
        return false;
      }

-      pkt.protocol_version = buffer[0];
-      pkt.role = static_cast<DeviceRole>(buffer[1]);
-      pkt.device_id_short = static_cast<uint16_t>(buffer[2] << 8) | buffer[3];
-      pkt.payload_type = static_cast<PayloadType>(buffer[4]);
-      pkt.payload_len = len - 7;
+      pkt.msg_kind = static_cast<LoraMsgKind>(msg_kind);
+      pkt.device_id_short = static_cast<uint16_t>(buffer[1] << 8) | buffer[2];
+      pkt.payload_len = len - 5;
      if (pkt.payload_len > LORA_MAX_PAYLOAD) {
+        note_reject(RxRejectReason::LengthMismatch);
        return false;
      }
-      memcpy(pkt.payload, &buffer[5], pkt.payload_len);
-      pkt.rssi_dbm = static_cast<int16_t>(LoRa.packetRssi());
-      pkt.snr_db = LoRa.packetSnr();
+      memcpy(pkt.payload, &buffer[3], pkt.payload_len);
+      pkt.rssi_dbm = g_last_rx_rssi_dbm;
+      pkt.snr_db = g_last_rx_snr_db;
      return true;
    }

@@ -103,6 +186,52 @@ bool lora_receive(LoraPacket &pkt, uint32_t timeout_ms) {
  }
 }

+void lora_idle() {
+  LoRa.idle();
+}
+
 void lora_sleep() {
  LoRa.sleep();
 }
+
+void lora_receive_continuous() {
+  LoRa.receive();
+}
+
+bool lora_receive_window(LoraPacket &pkt, uint32_t timeout_ms) {
+  if (timeout_ms == 0) {
+    return false;
+  }
+  g_last_rx_signal_valid = false;
+  g_last_rx_rssi_dbm = 0;
+  g_last_rx_snr_db = 0.0f;
+  LoRa.receive();
+  bool got = lora_receive(pkt, timeout_ms);
+  LoRa.sleep();
+  return got;
+}
+
+uint32_t lora_airtime_ms(size_t packet_len) {
+  if (packet_len == 0) {
+    return 0;
+  }
+
+  const double bw = static_cast<double>(LORA_BANDWIDTH);
+  const double sf = static_cast<double>(LORA_SPREADING_FACTOR);
+  const double cr = static_cast<double>(LORA_CODING_RATE - 4); // coding rate denominator: 4/(4+cr)
+  const double tsym = (1 << LORA_SPREADING_FACTOR) / bw;
+  const double t_preamble = (static_cast<double>(LORA_PREAMBLE_LEN) + 4.25) * tsym;
+
+  const bool low_data_rate_opt = (LORA_SPREADING_FACTOR >= 11) && (LORA_BANDWIDTH <= 125000);
+  const double de = low_data_rate_opt ? 1.0 : 0.0;
+  const double ih = 0.0;
+  const double crc = 1.0;
+
+  const double payload_symb_nb = 8.0 + max(
+    ceil((8.0 * packet_len - 4.0 * sf + 28.0 + 16.0 * crc - 20.0 * ih) / (4.0 * (sf - 2.0 * de))) * (cr + 4.0),
+    0.0);
+  const double t_payload = payload_symb_nb * tsym;
+  const double t_packet = t_preamble + t_payload;
+
+  return static_cast<uint32_t>(ceil(t_packet * 1000.0));
+}
--- a/src/main.cpp
+++ b/src/main.cpp
--- a/src/meter_driver.cpp
+++ b/src/meter_driver.cpp
@@ -4,167 +4,31 @@
 #include <stdlib.h>
 #include <string.h>

-static constexpr uint32_t METER_READ_TIMEOUT_MS = 2000;
-static constexpr size_t SML_BUFFER_SIZE = 2048;
+static constexpr uint32_t METER_FRAME_TIMEOUT_MS = 1500;
+static constexpr size_t METER_FRAME_MAX = 512;

-static const uint8_t OBIS_ENERGY_TOTAL[6] = {0x01, 0x00, 0x01, 0x08, 0x00, 0xFF};
-static const uint8_t OBIS_TOTAL_POWER[6] = {0x01, 0x00, 0x10, 0x07, 0x00, 0xFF};
-static const uint8_t OBIS_P1[6] = {0x01, 0x00, 0x24, 0x07, 0x00, 0xFF};
-static const uint8_t OBIS_P2[6] = {0x01, 0x00, 0x38, 0x07, 0x00, 0xFF};
-static const uint8_t OBIS_P3[6] = {0x01, 0x00, 0x4C, 0x07, 0x00, 0xFF};
-static const uint8_t OBIS_V1[6] = {0x01, 0x00, 0x20, 0x07, 0x00, 0xFF};
-static const uint8_t OBIS_V2[6] = {0x01, 0x00, 0x34, 0x07, 0x00, 0xFF};
-static const uint8_t OBIS_V3[6] = {0x01, 0x00, 0x48, 0x07, 0x00, 0xFF};
+enum class MeterRxState : uint8_t {
+  WaitStart = 0,
+  InFrame = 1
+};

-static bool find_obis_value(const uint8_t *buf, size_t len, const uint8_t *obis, float &out_value) {
-  for (size_t i = 0; i + 6 < len; ++i) {
-    if (memcmp(&buf[i], obis, 6) == 0) {
-      int8_t scaler = 0;
-      bool scaler_found = false;
-      bool value_found = false;
-      int64_t value = 0;
-      size_t cursor = i + 6;
-      size_t limit = (i + 6 + 120 < len) ? i + 6 + 120 : len;
+struct MeterPort {
+  HardwareSerial *serial;
+  MeterRxState state;
+  char frame_buf[METER_FRAME_MAX + 1];
+  size_t frame_len;
+  uint32_t last_rx_ms;
+  uint32_t bytes_rx;
+  uint32_t frames_ok;
+  uint32_t frames_parse_fail;
+  uint32_t rx_overflow;
+  uint32_t rx_timeout;
+  uint32_t last_energy_kwh;
+  bool has_energy;
+};

-      while (cursor < limit) {
-        uint8_t tl = buf[cursor++];
-        if (tl == 0x00) {
-          continue;
-        }
-        uint8_t type = (tl >> 4) & 0x0F;
-        uint8_t tlen = tl & 0x0F;
-        if (tlen == 0 || cursor + tlen > len) {
-          continue;
-        }
-
-        if (type == 0x05 || type == 0x06) {
-          int64_t val = 0;
-          for (uint8_t b = 0; b < tlen; ++b) {
-            val = (val << 8) | buf[cursor + b];
-          }
-          if (type == 0x05) {
-            int64_t sign_bit = 1LL << ((tlen * 8) - 1);
-            if (val & sign_bit) {
-              int64_t mask = (1LL << (tlen * 8)) - 1;
-              val = -((~val + 1) & mask);
-            }
-          }
-
-          if (!scaler_found && tlen <= 2 && val >= -6 && val <= 6) {
-            scaler = static_cast<int8_t>(val);
-            scaler_found = true;
-          } else if (!value_found) {
-            value = val;
-            value_found = true;
-          }
-        }
-        cursor += tlen;
-        if (value_found && scaler_found) {
-          break;
-        }
-      }
-
-      if (value_found) {
-        out_value = static_cast<float>(value) * powf(10.0f, scaler);
-        return true;
-      }
-    }
-  }
-  return false;
-}
-
-void meter_init() {
-  Serial2.begin(9600, SERIAL_7E1, PIN_METER_RX, -1);
-}
-
-static bool meter_read_sml(MeterData &data) {
-  uint8_t buffer[SML_BUFFER_SIZE];
-  size_t len = 0;
-  bool started = false;
-  uint32_t start = millis();
-  const uint8_t start_seq[] = {0x1B, 0x1B, 0x1B, 0x1B, 0x01, 0x01, 0x01, 0x01};
-  const uint8_t end_seq[] = {0x1B, 0x1B, 0x1B, 0x1B, 0x1A};
-
-  while (millis() - start < METER_READ_TIMEOUT_MS) {
-    while (Serial2.available()) {
-      uint8_t b = Serial2.read();
-      if (!started) {
-        buffer[len++] = b;
-        if (len >= sizeof(start_seq)) {
-          if (memcmp(&buffer[len - sizeof(start_seq)], start_seq, sizeof(start_seq)) == 0) {
-            started = true;
-            len = 0;
-          }
-        }
-        if (len >= sizeof(buffer)) {
-          len = 0;
-        }
-      } else {
-        if (len < sizeof(buffer)) {
-          buffer[len++] = b;
-          if (len >= sizeof(end_seq)) {
-            if (memcmp(&buffer[len - sizeof(end_seq)], end_seq, sizeof(end_seq)) == 0) {
-              start = millis();
-              goto parse_frame;
-            }
-          }
-        }
-      }
-    }
-    delay(5);
-  }
-
-parse_frame:
-  if (!started || len == 0) {
-    return false;
-  }
-
-  data.energy_total_kwh = NAN;
-  data.total_power_w = NAN;
-  data.phase_power_w[0] = NAN;
-  data.phase_power_w[1] = NAN;
-  data.phase_power_w[2] = NAN;
-  data.phase_voltage_v[0] = NAN;
-  data.phase_voltage_v[1] = NAN;
-  data.phase_voltage_v[2] = NAN;
-
-  bool ok = true;
-  float value = 0.0f;
-
-  if (find_obis_value(buffer, len, OBIS_ENERGY_TOTAL, value)) {
-    data.energy_total_kwh = value;
-  } else {
-    ok = false;
-  }
-
-  if (find_obis_value(buffer, len, OBIS_TOTAL_POWER, value)) {
-    data.total_power_w = value;
-  } else {
-    ok = false;
-  }
-
-  if (find_obis_value(buffer, len, OBIS_P1, value)) {
-    data.phase_power_w[0] = value;
-  }
-  if (find_obis_value(buffer, len, OBIS_P2, value)) {
-    data.phase_power_w[1] = value;
-  }
-  if (find_obis_value(buffer, len, OBIS_P3, value)) {
-    data.phase_power_w[2] = value;
-  }
-  if (find_obis_value(buffer, len, OBIS_V1, value)) {
-    data.phase_voltage_v[0] = value;
-  }
-  if (find_obis_value(buffer, len, OBIS_V2, value)) {
-    data.phase_voltage_v[1] = value;
-  }
-  if (find_obis_value(buffer, len, OBIS_V3, value)) {
-    data.phase_voltage_v[2] = value;
-  }
-
-  data.valid = ok;
-  return ok;
-}
+static MeterPort g_ports[METER_COUNT] = {};
+static uint32_t g_last_log_ms = 0;

 static bool parse_obis_ascii_value(const char *line, const char *obis, float &out_value) {
  const char *p = strstr(line, obis);
@@ -201,146 +65,142 @@ static bool parse_obis_ascii_value(const char *line, const char *obis, float &ou
  return true;
 }

-static bool parse_obis_ascii_unit_scale(const char *line, const char *obis, float &value) {
-  const char *p = strstr(line, obis);
-  if (!p) {
-    return false;
-  }
-  const char *asterisk = strchr(p, '*');
-  if (!asterisk) {
-    return false;
-  }
-  const char *end = strchr(asterisk, ')');
-  if (!end) {
-    return false;
-  }
-  char unit_buf[8];
-  size_t ulen = 0;
-  for (const char *c = asterisk + 1; c < end && ulen + 1 < sizeof(unit_buf); ++c) {
-    if (*c == ' ') {
-      continue;
-    }
-    unit_buf[ulen++] = *c;
-  }
-  unit_buf[ulen] = '\0';
-  if (ulen == 0) {
-    return false;
-  }
-  if (strcmp(unit_buf, "Wh") == 0) {
-    value *= 0.001f;
-    return true;
-  }
-  return false;
-}
-
-static bool meter_read_ascii(MeterData &data) {
-  const uint32_t start_ms = millis();
-  bool in_telegram = false;
-  bool got_any = false;
-
-  bool energy_ok = false;
-  bool total_p_ok = false;
-  bool p1_ok = false;
-  bool p2_ok = false;
-  bool p3_ok = false;
-  bool v1_ok = false;
-  bool v2_ok = false;
-  bool v3_ok = false;
-
+static bool parse_energy_kwh_floor(const char *frame, size_t len, uint32_t &out_kwh) {
  char line[128];
  size_t line_len = 0;
-
-  while (millis() - start_ms < METER_READ_TIMEOUT_MS) {
-    while (Serial2.available()) {
-      char c = static_cast<char>(Serial2.read());
-      if (!in_telegram) {
-        if (c == '/') {
-          in_telegram = true;
-          line_len = 0;
-          line[line_len++] = c;
-        }
-        continue;
-      }
-
+  for (size_t i = 0; i < len; ++i) {
+    char c = frame[i];
    if (c == '\r') {
      continue;
    }
-      if (c == '\n') {
+    if (c == '\n' || c == '!') {
      line[line_len] = '\0';
-        if (line[0] == '!') {
-          return got_any;
-        }
-
      float value = NAN;
-        if (parse_obis_ascii_value(line, "1-0:1.8.0", value)) {
-          parse_obis_ascii_unit_scale(line, "1-0:1.8.0", value);
-          data.energy_total_kwh = value;
-          energy_ok = true;
-          got_any = true;
+      if (parse_obis_ascii_value(line, "1-0:1.8.0", value) && !isnan(value) && value >= 0.0f) {
+        out_kwh = static_cast<uint32_t>(floorf(value));
+        return true;
      }
-        if (parse_obis_ascii_value(line, "1-0:16.7.0", value)) {
-          data.total_power_w = value;
-          total_p_ok = true;
-          got_any = true;
-        }
-        if (parse_obis_ascii_value(line, "1-0:36.7.0", value)) {
-          data.phase_power_w[0] = value;
-          p1_ok = true;
-          got_any = true;
-        }
-        if (parse_obis_ascii_value(line, "1-0:56.7.0", value)) {
-          data.phase_power_w[1] = value;
-          p2_ok = true;
-          got_any = true;
-        }
-        if (parse_obis_ascii_value(line, "1-0:76.7.0", value)) {
-          data.phase_power_w[2] = value;
-          p3_ok = true;
-          got_any = true;
-        }
-        if (parse_obis_ascii_value(line, "1-0:32.7.0", value)) {
-          data.phase_voltage_v[0] = value;
-          v1_ok = true;
-          got_any = true;
-        }
-        if (parse_obis_ascii_value(line, "1-0:52.7.0", value)) {
-          data.phase_voltage_v[1] = value;
-          v2_ok = true;
-          got_any = true;
-        }
-        if (parse_obis_ascii_value(line, "1-0:72.7.0", value)) {
-          data.phase_voltage_v[2] = value;
-          v3_ok = true;
-          got_any = true;
-        }
-
      line_len = 0;
+      if (c == '!') {
+        break;
+      }
      continue;
    }
    if (line_len + 1 < sizeof(line)) {
      line[line_len++] = c;
    }
  }
-    delay(5);
+  return false;
 }

-  data.valid = energy_ok || total_p_ok || p1_ok || p2_ok || p3_ok || v1_ok || v2_ok || v3_ok;
-  return data.valid;
+static void meter_debug_log() {
+  if (!SERIAL_DEBUG_MODE) {
+    return;
+  }
+  uint32_t now_ms = millis();
+  if (now_ms - g_last_log_ms < 60000) {
+    return;
+  }
+  g_last_log_ms = now_ms;
+  for (uint8_t i = 0; i < METER_COUNT; ++i) {
+    const MeterPort &p = g_ports[i];
+    Serial.printf("meter%u: ok=%lu parse_fail=%lu overflow=%lu timeout=%lu bytes=%lu e=%lu valid=%u\n",
+                  static_cast<unsigned>(i + 1),
+                  static_cast<unsigned long>(p.frames_ok),
+                  static_cast<unsigned long>(p.frames_parse_fail),
+                  static_cast<unsigned long>(p.rx_overflow),
+                  static_cast<unsigned long>(p.rx_timeout),
+                  static_cast<unsigned long>(p.bytes_rx),
+                  static_cast<unsigned long>(p.last_energy_kwh),
+                  p.has_energy ? 1 : 0);
+  }
 }

-bool meter_read(MeterData &data) {
-  data.energy_total_kwh = NAN;
-  data.total_power_w = NAN;
-  data.phase_power_w[0] = NAN;
-  data.phase_power_w[1] = NAN;
-  data.phase_power_w[2] = NAN;
-  data.phase_voltage_v[0] = NAN;
-  data.phase_voltage_v[1] = NAN;
-  data.phase_voltage_v[2] = NAN;
-  data.valid = false;
+void meter_init() {
+  g_ports[0].serial = &Serial2;
+  g_ports[0].serial->begin(9600, SERIAL_7E1, PIN_METER1_RX, -1);
+  g_ports[0].state = MeterRxState::WaitStart;

-  if (meter_read_ascii(data)) {
+  if (METER_COUNT >= 2) {
+    g_ports[1].serial = &Serial1;
+    g_ports[1].serial->begin(9600, SERIAL_7E1, PIN_METER2_RX, -1);
+    g_ports[1].state = MeterRxState::WaitStart;
+  }
+
+  if (METER_COUNT >= 3) {
+    g_ports[2].serial = &Serial;
+    g_ports[2].serial->begin(9600, SERIAL_7E1, PIN_METER3_RX, -1);
+    g_ports[2].state = MeterRxState::WaitStart;
+  }
+}
+
+static void meter_poll_port(MeterPort &port) {
+  if (!port.serial) {
+    return;
+  }
+  uint32_t now_ms = millis();
+  if (port.state == MeterRxState::InFrame && (now_ms - port.last_rx_ms > METER_FRAME_TIMEOUT_MS)) {
+    port.rx_timeout++;
+    port.state = MeterRxState::WaitStart;
+    port.frame_len = 0;
+  }
+
+  while (port.serial->available()) {
+    char c = static_cast<char>(port.serial->read());
+    port.bytes_rx++;
+    port.last_rx_ms = now_ms;
+
+    if (port.state == MeterRxState::WaitStart) {
+      if (c == '/') {
+        port.state = MeterRxState::InFrame;
+        port.frame_len = 0;
+        port.frame_buf[port.frame_len++] = c;
+      }
+      continue;
+    }
+
+    if (port.frame_len + 1 >= sizeof(port.frame_buf)) {
+      port.rx_overflow++;
+      port.state = MeterRxState::WaitStart;
+      port.frame_len = 0;
+      continue;
+    }
+
+    port.frame_buf[port.frame_len++] = c;
+    if (c == '!') {
+      port.frame_buf[port.frame_len] = '\0';
+      uint32_t energy_kwh = 0;
+      if (parse_energy_kwh_floor(port.frame_buf, port.frame_len, energy_kwh)) {
+        port.last_energy_kwh = energy_kwh;
+        port.has_energy = true;
+        port.frames_ok++;
+      } else {
+        port.frames_parse_fail++;
+      }
+      port.state = MeterRxState::WaitStart;
+      port.frame_len = 0;
+    }
+  }
+}
+
+void meter_poll() {
+  for (uint8_t i = 0; i < METER_COUNT; ++i) {
+    meter_poll_port(g_ports[i]);
+  }
+  meter_debug_log();
+}
+
+uint8_t meter_count() {
+  return METER_COUNT;
+}
+
+bool meter_get_last_energy_kwh(uint8_t meter_idx, uint32_t &out_energy_kwh) {
+  if (meter_idx >= METER_COUNT) {
+    return false;
+  }
+  if (!g_ports[meter_idx].has_energy) {
+    return false;
+  }
+  out_energy_kwh = g_ports[meter_idx].last_energy_kwh;
  return true;
 }
-  return meter_read_sml(data);
-}
--- a/src/mqtt_client.cpp
+++ b/src/mqtt_client.cpp
@@ -10,6 +10,19 @@ static PubSubClient mqtt_client(wifi_client);
 static WifiMqttConfig g_cfg;
 static String g_client_id;

+static const char *fault_text(FaultType fault) {
+  switch (fault) {
+    case FaultType::MeterRead:
+      return "meter";
+    case FaultType::Decode:
+      return "decode";
+    case FaultType::LoraTx:
+      return "loratx";
+    default:
+      return "none";
+  }
+}
+
 void mqtt_init(const WifiMqttConfig &config, const char *device_id) {
  g_cfg = config;
  mqtt_client.setServer(config.mqtt_host.c_str(), config.mqtt_port);
@@ -66,10 +79,9 @@ bool mqtt_publish_faults(const char *device_id, const FaultCounters &counters, F
  doc["err_m"] = counters.meter_read_fail;
  doc["err_d"] = counters.decode_fail;
  doc["err_tx"] = counters.lora_tx_fail;
-  if (last_error != FaultType::None) {
  doc["err_last"] = static_cast<uint8_t>(last_error);
-    doc["err_last_age"] = last_error_age_sec;
-  }
+  doc["err_last_text"] = fault_text(last_error);
+  doc["err_last_age"] = last_error != FaultType::None ? last_error_age_sec : 0;

  String payload;
  size_t len = serializeJson(doc, payload);
@@ -126,9 +138,6 @@ bool mqtt_publish_discovery(const char *device_id) {
  bool ok = true;
  ok = ok && publish_discovery_sensor(device_id, "energy", "Energy", "kWh", "energy", state_topic.c_str(), "{{ value_json.e_kwh }}");
  ok = ok && publish_discovery_sensor(device_id, "power", "Power", "W", "power", state_topic.c_str(), "{{ value_json.p_w }}");
-  ok = ok && publish_discovery_sensor(device_id, "v1", "Voltage L1", "V", "voltage", state_topic.c_str(), "{{ value_json.v1_v }}");
-  ok = ok && publish_discovery_sensor(device_id, "v2", "Voltage L2", "V", "voltage", state_topic.c_str(), "{{ value_json.v2_v }}");
-  ok = ok && publish_discovery_sensor(device_id, "v3", "Voltage L3", "V", "voltage", state_topic.c_str(), "{{ value_json.v3_v }}");
  ok = ok && publish_discovery_sensor(device_id, "p1", "Power L1", "W", "power", state_topic.c_str(), "{{ value_json.p1_w }}");
  ok = ok && publish_discovery_sensor(device_id, "p2", "Power L2", "W", "power", state_topic.c_str(), "{{ value_json.p2_w }}");
  ok = ok && publish_discovery_sensor(device_id, "p3", "Power L3", "W", "power", state_topic.c_str(), "{{ value_json.p3_w }}");
@@ -141,6 +150,8 @@ bool mqtt_publish_discovery(const char *device_id) {
  ok = ok && publish_discovery_sensor(device_id, "err_m", "Meter Read Errors", "count", "", faults_topic.c_str(), "{{ value_json.err_m }}");
  ok = ok && publish_discovery_sensor(device_id, "err_d", "Decode Errors", "count", "", faults_topic.c_str(), "{{ value_json.err_d }}");
  ok = ok && publish_discovery_sensor(device_id, "err_tx", "LoRa TX Errors", "count", "", faults_topic.c_str(), "{{ value_json.err_tx }}");
+  ok = ok && publish_discovery_sensor(device_id, "err_last", "Last Error Code", "", "", faults_topic.c_str(), "{{ value_json.err_last }}");
+  ok = ok && publish_discovery_sensor(device_id, "err_last_text", "Last Error", "", "", faults_topic.c_str(), "{{ value_json.err_last_text }}");
  ok = ok && publish_discovery_sensor(device_id, "err_last_age", "Last Error Age", "s", "", faults_topic.c_str(), "{{ value_json.err_last_age }}");
  return ok;
 }
--- a/src/payload_codec.cpp
+++ b/src/payload_codec.cpp
@@ -0,0 +1,406 @@
+#include "payload_codec.h"
+#include <limits.h>
+
+static constexpr uint16_t kMagic = 0xDDB3;
+static constexpr uint8_t kSchema = 2;
+static constexpr uint8_t kFlags = 0x01;
+static constexpr size_t kMaxSamples = 30;
+static constexpr uint8_t kPayloadSchemaLegacy = 0;
+static constexpr uint8_t kPayloadSchemaEnergyMulti = 1;
+
+static void write_u16_le(uint8_t *dst, uint16_t value) {
+  dst[0] = static_cast<uint8_t>(value & 0xFF);
+  dst[1] = static_cast<uint8_t>((value >> 8) & 0xFF);
+}
+
+static void write_u32_le(uint8_t *dst, uint32_t value) {
+  dst[0] = static_cast<uint8_t>(value & 0xFF);
+  dst[1] = static_cast<uint8_t>((value >> 8) & 0xFF);
+  dst[2] = static_cast<uint8_t>((value >> 16) & 0xFF);
+  dst[3] = static_cast<uint8_t>((value >> 24) & 0xFF);
+}
+
+static uint16_t read_u16_le(const uint8_t *src) {
+  return static_cast<uint16_t>(src[0]) | (static_cast<uint16_t>(src[1]) << 8);
+}
+
+static uint32_t read_u32_le(const uint8_t *src) {
+  return static_cast<uint32_t>(src[0]) |
+         (static_cast<uint32_t>(src[1]) << 8) |
+         (static_cast<uint32_t>(src[2]) << 16) |
+         (static_cast<uint32_t>(src[3]) << 24);
+}
+
+size_t uleb128_encode(uint32_t v, uint8_t *out, size_t cap) {
+  size_t i = 0;
+  do {
+    if (i >= cap) {
+      return 0;
+    }
+    uint8_t byte = static_cast<uint8_t>(v & 0x7F);
+    v >>= 7;
+    if (v != 0) {
+      byte |= 0x80;
+    }
+    out[i++] = byte;
+  } while (v != 0);
+  return i;
+}
+
+bool uleb128_decode(const uint8_t *in, size_t len, size_t *pos, uint32_t *v) {
+  if (!in || !pos || !v) {
+    return false;
+  }
+  uint32_t result = 0;
+  uint8_t shift = 0;
+  size_t p = *pos;
+  for (uint8_t i = 0; i < 5; ++i) {
+    if (p >= len) {
+      return false;
+    }
+    uint8_t byte = in[p++];
+    if (i == 4 && (byte & 0xF0) != 0) {
+      return false;
+    }
+    result |= static_cast<uint32_t>(byte & 0x7F) << shift;
+    if ((byte & 0x80) == 0) {
+      *pos = p;
+      *v = result;
+      return true;
+    }
+    shift = static_cast<uint8_t>(shift + 7);
+  }
+  return false;
+}
+
+uint32_t zigzag32(int32_t x) {
+  return (static_cast<uint32_t>(x) << 1) ^ static_cast<uint32_t>(x >> 31);
+}
+
+int32_t unzigzag32(uint32_t u) {
+  return static_cast<int32_t>((u >> 1) ^ (static_cast<uint32_t>(-static_cast<int32_t>(u & 1))));
+}
+
+size_t svarint_encode(int32_t x, uint8_t *out, size_t cap) {
+  uint32_t zz = zigzag32(x);
+  return uleb128_encode(zz, out, cap);
+}
+
+bool svarint_decode(const uint8_t *in, size_t len, size_t *pos, int32_t *x) {
+  uint32_t u = 0;
+  if (!uleb128_decode(in, len, pos, &u)) {
+    return false;
+  }
+  *x = unzigzag32(u);
+  return true;
+}
+
+static bool ensure_capacity(size_t needed, size_t cap, size_t pos) {
+  return pos + needed <= cap;
+}
+
+bool encode_batch(const BatchInput &in, uint8_t *out, size_t out_cap, size_t *out_len) {
+  if (!out || !out_len) {
+    return false;
+  }
+  if (in.n > kMaxSamples) {
+    return false;
+  }
+  if (in.dt_s == 0) {
+    return false;
+  }
+  size_t pos = 0;
+  if (!ensure_capacity(23, out_cap, pos)) {
+    return false;
+  }
+  write_u16_le(&out[pos], kMagic);
+  pos += 2;
+  out[pos++] = kSchema;
+  out[pos++] = kFlags;
+  out[pos++] = in.schema_id;
+  write_u16_le(&out[pos], in.sender_id);
+  pos += 2;
+  write_u16_le(&out[pos], in.batch_id);
+  pos += 2;
+  write_u32_le(&out[pos], in.t_last);
+  pos += 4;
+  out[pos++] = in.dt_s;
+  out[pos++] = in.n;
+  write_u16_le(&out[pos], in.battery_mV);
+  pos += 2;
+  out[pos++] = in.err_m;
+  out[pos++] = in.err_d;
+  out[pos++] = in.err_tx;
+  out[pos++] = in.err_last;
+  out[pos++] = in.err_rx_reject;
+  out[pos++] = in.meter_count;
+
+  if (in.n == 0) {
+    *out_len = pos;
+    return true;
+  }
+
+  if (in.schema_id == kPayloadSchemaEnergyMulti) {
+    if (in.meter_count == 0 || in.meter_count > 3) {
+      return false;
+    }
+    if (!ensure_capacity(static_cast<size_t>(in.n) * 12, out_cap, pos)) {
+      return false;
+    }
+    for (uint8_t i = 0; i < in.n; ++i) {
+      write_u32_le(&out[pos], in.energy1_kwh[i]);
+      pos += 4;
+      write_u32_le(&out[pos], in.energy2_kwh[i]);
+      pos += 4;
+      write_u32_le(&out[pos], in.energy3_kwh[i]);
+      pos += 4;
+    }
+    *out_len = pos;
+    return true;
+  }
+
+  if (!ensure_capacity(4, out_cap, pos)) {
+    return false;
+  }
+  write_u32_le(&out[pos], in.energy_wh[0]);
+  pos += 4;
+  for (uint8_t i = 1; i < in.n; ++i) {
+    if (in.energy_wh[i] < in.energy_wh[i - 1]) {
+      return false;
+    }
+    uint32_t delta = in.energy_wh[i] - in.energy_wh[i - 1];
+    size_t wrote = uleb128_encode(delta, &out[pos], out_cap - pos);
+    if (wrote == 0) {
+      return false;
+    }
+    pos += wrote;
+  }
+
+  auto encode_phase = [&](const int16_t *phase) -> bool {
+    if (!ensure_capacity(2, out_cap, pos)) {
+      return false;
+    }
+    write_u16_le(&out[pos], static_cast<uint16_t>(phase[0]));
+    pos += 2;
+    for (uint8_t i = 1; i < in.n; ++i) {
+      int32_t delta = static_cast<int32_t>(phase[i]) - static_cast<int32_t>(phase[i - 1]);
+      size_t wrote = svarint_encode(delta, &out[pos], out_cap - pos);
+      if (wrote == 0) {
+        return false;
+      }
+      pos += wrote;
+    }
+    return true;
+  };
+
+  if (!encode_phase(in.p1_w)) {
+    return false;
+  }
+  if (!encode_phase(in.p2_w)) {
+    return false;
+  }
+  if (!encode_phase(in.p3_w)) {
+    return false;
+  }
+
+  *out_len = pos;
+  return true;
+}
+
+bool decode_batch(const uint8_t *buf, size_t len, BatchInput *out) {
+  if (!buf || !out) {
+    return false;
+  }
+  size_t pos = 0;
+  if (len < 23) {
+    return false;
+  }
+  uint16_t magic = read_u16_le(&buf[pos]);
+  pos += 2;
+  uint8_t schema = buf[pos++];
+  uint8_t flags = buf[pos++];
+  if (magic != kMagic || schema != kSchema || (flags & 0x01) == 0) {
+    return false;
+  }
+  out->schema_id = buf[pos++];
+  out->sender_id = read_u16_le(&buf[pos]);
+  pos += 2;
+  out->batch_id = read_u16_le(&buf[pos]);
+  pos += 2;
+  out->t_last = read_u32_le(&buf[pos]);
+  pos += 4;
+  out->dt_s = buf[pos++];
+  out->n = buf[pos++];
+  out->battery_mV = read_u16_le(&buf[pos]);
+  pos += 2;
+  out->err_m = buf[pos++];
+  out->err_d = buf[pos++];
+  out->err_tx = buf[pos++];
+  out->err_last = buf[pos++];
+  out->err_rx_reject = buf[pos++];
+  out->meter_count = buf[pos++];
+
+  if (out->n > kMaxSamples || out->dt_s == 0) {
+    return false;
+  }
+  if (out->n == 0) {
+    for (uint8_t i = 0; i < kMaxSamples; ++i) {
+      out->energy_wh[i] = 0;
+      out->p1_w[i] = 0;
+      out->p2_w[i] = 0;
+      out->p3_w[i] = 0;
+    }
+    return pos == len;
+  }
+  if (out->schema_id == kPayloadSchemaEnergyMulti) {
+    if (out->meter_count == 0 || out->meter_count > 3) {
+      return false;
+    }
+    if (pos + static_cast<size_t>(out->n) * 12 > len) {
+      return false;
+    }
+    for (uint8_t i = 0; i < out->n; ++i) {
+      out->energy1_kwh[i] = read_u32_le(&buf[pos]);
+      pos += 4;
+      out->energy2_kwh[i] = read_u32_le(&buf[pos]);
+      pos += 4;
+      out->energy3_kwh[i] = read_u32_le(&buf[pos]);
+      pos += 4;
+    }
+    for (uint8_t i = out->n; i < kMaxSamples; ++i) {
+      out->energy1_kwh[i] = 0;
+      out->energy2_kwh[i] = 0;
+      out->energy3_kwh[i] = 0;
+    }
+    return pos == len;
+  }
+
+  if (pos + 4 > len) {
+    return false;
+  }
+  out->energy_wh[0] = read_u32_le(&buf[pos]);
+  pos += 4;
+  for (uint8_t i = 1; i < out->n; ++i) {
+    uint32_t delta = 0;
+    if (!uleb128_decode(buf, len, &pos, &delta)) {
+      return false;
+    }
+    uint64_t sum = static_cast<uint64_t>(out->energy_wh[i - 1]) + static_cast<uint64_t>(delta);
+    if (sum > UINT32_MAX) {
+      return false;
+    }
+    out->energy_wh[i] = static_cast<uint32_t>(sum);
+  }
+
+  auto decode_phase = [&](int16_t *phase) -> bool {
+    if (pos + 2 > len) {
+      return false;
+    }
+    phase[0] = static_cast<int16_t>(read_u16_le(&buf[pos]));
+    pos += 2;
+    int32_t prev = static_cast<int32_t>(phase[0]);
+    for (uint8_t i = 1; i < out->n; ++i) {
+      int32_t delta = 0;
+      if (!svarint_decode(buf, len, &pos, &delta)) {
+        return false;
+      }
+      int32_t value = prev + delta;
+      if (value < INT16_MIN || value > INT16_MAX) {
+        return false;
+      }
+      phase[i] = static_cast<int16_t>(value);
+      prev = value;
+    }
+    return true;
+  };
+
+  if (!decode_phase(out->p1_w)) {
+    return false;
+  }
+  if (!decode_phase(out->p2_w)) {
+    return false;
+  }
+  if (!decode_phase(out->p3_w)) {
+    return false;
+  }
+
+  for (uint8_t i = out->n; i < kMaxSamples; ++i) {
+    out->energy_wh[i] = 0;
+    out->p1_w[i] = 0;
+    out->p2_w[i] = 0;
+    out->p3_w[i] = 0;
+  }
+
+  return pos == len;
+}
+
+#ifdef PAYLOAD_CODEC_TEST
+bool payload_codec_self_test() {
+  BatchInput in = {};
+  in.schema_id = kPayloadSchemaLegacy;
+  in.sender_id = 1;
+  in.batch_id = 42;
+  in.t_last = 1700000000;
+  in.dt_s = 1;
+  in.n = 5;
+  in.battery_mV = 3750;
+  in.err_m = 2;
+  in.err_d = 1;
+  in.err_tx = 3;
+  in.err_last = 2;
+  in.err_rx_reject = 1;
+  in.meter_count = 0;
+  in.energy_wh[0] = 100000;
+  in.energy_wh[1] = 100001;
+  in.energy_wh[2] = 100050;
+  in.energy_wh[3] = 100050;
+  in.energy_wh[4] = 100200;
+  in.p1_w[0] = -120;
+  in.p1_w[1] = -90;
+  in.p1_w[2] = 1910;
+  in.p1_w[3] = -90;
+  in.p1_w[4] = 500;
+  in.p2_w[0] = 50;
+  in.p2_w[1] = -1950;
+  in.p2_w[2] = 60;
+  in.p2_w[3] = 2060;
+  in.p2_w[4] = -10;
+  in.p3_w[0] = 0;
+  in.p3_w[1] = 10;
+  in.p3_w[2] = -1990;
+  in.p3_w[3] = 10;
+  in.p3_w[4] = 20;
+
+  uint8_t buf[256];
+  size_t len = 0;
+  if (!encode_batch(in, buf, sizeof(buf), &len)) {
+    Serial.println("payload_codec_self_test: encode failed");
+    return false;
+  }
+
+  BatchInput out = {};
+  if (!decode_batch(buf, len, &out)) {
+    Serial.println("payload_codec_self_test: decode failed");
+    return false;
+  }
+
+  if (out.sender_id != in.sender_id || out.batch_id != in.batch_id || out.t_last != in.t_last ||
+      out.dt_s != in.dt_s || out.n != in.n || out.battery_mV != in.battery_mV ||
+      out.err_m != in.err_m || out.err_d != in.err_d || out.err_tx != in.err_tx || out.err_last != in.err_last ||
+      out.err_rx_reject != in.err_rx_reject) {
+    Serial.println("payload_codec_self_test: header mismatch");
+    return false;
+  }
+
+  for (uint8_t i = 0; i < in.n; ++i) {
+    if (out.energy_wh[i] != in.energy_wh[i] || out.p1_w[i] != in.p1_w[i] || out.p2_w[i] != in.p2_w[i] ||
+        out.p3_w[i] != in.p3_w[i]) {
+      Serial.println("payload_codec_self_test: sample mismatch");
+      return false;
+    }
+  }
+
+  Serial.printf("payload_codec_self_test: ok len=%u\n", static_cast<unsigned>(len));
+  return true;
+}
+#endif
--- a/src/payload_codec.h
+++ b/src/payload_codec.h
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <Arduino.h>
+
+struct BatchInput {
+  uint8_t schema_id;
+  uint16_t sender_id;
+  uint16_t batch_id;
+  uint32_t t_last;
+  uint8_t dt_s;
+  uint8_t n;
+  uint8_t meter_count;
+  uint16_t battery_mV;
+  uint8_t err_m;
+  uint8_t err_d;
+  uint8_t err_tx;
+  uint8_t err_last;
+  uint8_t err_rx_reject;
+  uint32_t energy1_kwh[30];
+  uint32_t energy2_kwh[30];
+  uint32_t energy3_kwh[30];
+  uint32_t energy_wh[30];
+  int16_t p1_w[30];
+  int16_t p2_w[30];
+  int16_t p3_w[30];
+};
+
+bool encode_batch(const BatchInput &in, uint8_t *out, size_t out_cap, size_t *out_len);
+bool decode_batch(const uint8_t *buf, size_t len, BatchInput *out);
+
+size_t uleb128_encode(uint32_t v, uint8_t *out, size_t cap);
+bool uleb128_decode(const uint8_t *in, size_t len, size_t *pos, uint32_t *v);
+
+uint32_t zigzag32(int32_t x);
+int32_t unzigzag32(uint32_t u);
+
+size_t svarint_encode(int32_t x, uint8_t *out, size_t cap);
+bool svarint_decode(const uint8_t *in, size_t len, size_t *pos, int32_t *x);
+
+#ifdef PAYLOAD_CODEC_TEST
+bool payload_codec_self_test();
+#endif
--- a/src/power_manager.cpp
+++ b/src/power_manager.cpp
@@ -6,11 +6,13 @@
 #include <esp_sleep.h>

 static constexpr float BATTERY_DIVIDER = 2.0f;
-static constexpr float BATTERY_CAL = 1.0f;
 static constexpr float ADC_REF_V = 3.3f;

 void power_sender_init() {
+  setCpuFrequencyMhz(80);
+  WiFi.mode(WIFI_OFF);
  esp_wifi_stop();
+  esp_wifi_deinit();
  btStop();
  analogReadResolution(12);
  pinMode(PIN_BAT_ADC, INPUT);
@@ -22,22 +24,79 @@ void power_receiver_init() {
  pinMode(PIN_BAT_ADC, INPUT);
 }

-void read_battery(MeterData &data) {
-  const int samples = 8;
-  uint32_t sum = 0;
-  for (int i = 0; i < samples; ++i) {
-    sum += analogRead(PIN_BAT_ADC);
-    delay(5);
+void power_configure_unused_pins_sender() {
+  // Board-specific: only touch pins that are known unused and safe on TTGO LoRa32 v1.6.1
+  const uint8_t pins[] = {32, 33};
+  for (uint8_t pin : pins) {
+    pinMode(pin, INPUT_PULLDOWN);
  }
-  float avg = static_cast<float>(sum) / samples;
+}
+
+void read_battery(MeterData &data) {
+  uint32_t sum = 0;
+  uint16_t samples[5] = {};
+  for (uint8_t i = 0; i < 5; ++i) {
+    samples[i] = analogRead(PIN_BAT_ADC);
+    sum += samples[i];
+  }
+  float avg = static_cast<float>(sum) / 5.0f;
  float v = (avg / 4095.0f) * ADC_REF_V * BATTERY_DIVIDER * BATTERY_CAL;
+  if (SERIAL_DEBUG_MODE) {
+    Serial.printf("bat_adc: %u %u %u %u %u avg=%.1f v=%.3f\n",
+                  samples[0], samples[1], samples[2], samples[3], samples[4],
+                  static_cast<double>(avg), static_cast<double>(v));
+  }

  data.battery_voltage_v = v;
  data.battery_percent = battery_percent_from_voltage(v);
 }

 uint8_t battery_percent_from_voltage(float voltage_v) {
-  float pct = (voltage_v - 3.0f) / (4.2f - 3.0f) * 100.0f;
+  if (isnan(voltage_v)) {
+    return 0;
+  }
+  struct LutPoint {
+    float v;
+    uint8_t pct;
+  };
+  static const LutPoint kCurve[] = {
+      {4.20f, 100},
+      {4.15f, 95},
+      {4.11f, 90},
+      {4.08f, 85},
+      {4.02f, 80},
+      {3.98f, 75},
+      {3.95f, 70},
+      {3.91f, 60},
+      {3.87f, 50},
+      {3.85f, 45},
+      {3.84f, 40},
+      {3.82f, 35},
+      {3.80f, 30},
+      {3.77f, 25},
+      {3.75f, 20},
+      {3.73f, 15},
+      {3.70f, 10},
+      {3.65f, 5},
+      {3.60f, 2},
+      {2.90f, 0},
+  };
+  if (voltage_v >= kCurve[0].v) {
+    return kCurve[0].pct;
+  }
+  if (voltage_v <= kCurve[sizeof(kCurve) / sizeof(kCurve[0]) - 1].v) {
+    return 0;
+  }
+  for (size_t i = 0; i + 1 < sizeof(kCurve) / sizeof(kCurve[0]); ++i) {
+    const LutPoint &hi = kCurve[i];
+    const LutPoint &lo = kCurve[i + 1];
+    if (voltage_v <= hi.v && voltage_v >= lo.v) {
+      float span = hi.v - lo.v;
+      if (span <= 0.0f) {
+        return lo.pct;
+      }
+      float t = (voltage_v - lo.v) / span;
+      float pct = lo.pct + t * (hi.pct - lo.pct);
      if (pct < 0.0f) {
        pct = 0.0f;
      }
@@ -46,6 +105,9 @@ uint8_t battery_percent_from_voltage(float voltage_v) {
      }
      return static_cast<uint8_t>(pct + 0.5f);
    }
+  }
+  return 0;
+}

 void light_sleep_ms(uint32_t ms) {
  if (ms == 0) {
--- a/src/rtc_ds3231.cpp
+++ b/src/rtc_ds3231.cpp
@@ -1,122 +0,0 @@
-#include "rtc_ds3231.h"
-#include "config.h"
-#include <Wire.h>
-#include <time.h>
-
-static constexpr uint8_t DS3231_ADDR = 0x68;
-
-static uint8_t bcd_to_dec(uint8_t val) {
-  return static_cast<uint8_t>((val >> 4) * 10 + (val & 0x0F));
-}
-
-static uint8_t dec_to_bcd(uint8_t val) {
-  return static_cast<uint8_t>(((val / 10) << 4) | (val % 10));
-}
-
-static time_t timegm_fallback(struct tm *tm_utc) {
-  if (!tm_utc) {
-    return static_cast<time_t>(-1);
-  }
-  char *old_tz = getenv("TZ");
-  setenv("TZ", "UTC0", 1);
-  tzset();
-  time_t t = mktime(tm_utc);
-  if (old_tz) {
-    setenv("TZ", old_tz, 1);
-  } else {
-    unsetenv("TZ");
-  }
-  tzset();
-  return t;
-}
-
-static bool read_registers(uint8_t start_reg, uint8_t *out, size_t len) {
-  if (!out || len == 0) {
-    return false;
-  }
-  Wire.beginTransmission(DS3231_ADDR);
-  Wire.write(start_reg);
-  if (Wire.endTransmission(false) != 0) {
-    return false;
-  }
-  size_t read = Wire.requestFrom(DS3231_ADDR, static_cast<uint8_t>(len));
-  if (read != len) {
-    return false;
-  }
-  for (size_t i = 0; i < len; ++i) {
-    out[i] = Wire.read();
-  }
-  return true;
-}
-
-static bool write_registers(uint8_t start_reg, const uint8_t *data, size_t len) {
-  if (!data || len == 0) {
-    return false;
-  }
-  Wire.beginTransmission(DS3231_ADDR);
-  Wire.write(start_reg);
-  for (size_t i = 0; i < len; ++i) {
-    Wire.write(data[i]);
-  }
-  return Wire.endTransmission() == 0;
-}
-
-bool rtc_ds3231_init() {
-  Wire.begin(PIN_OLED_SDA, PIN_OLED_SCL);
-  Wire.setClock(100000);
-  return rtc_ds3231_is_present();
-}
-
-bool rtc_ds3231_is_present() {
-  Wire.beginTransmission(DS3231_ADDR);
-  return Wire.endTransmission() == 0;
-}
-
-bool rtc_ds3231_read_epoch(uint32_t &epoch_utc) {
-  uint8_t regs[7] = {};
-  if (!read_registers(0x00, regs, sizeof(regs))) {
-    return false;
-  }
-
-  uint8_t sec = bcd_to_dec(regs[0] & 0x7F);
-  uint8_t min = bcd_to_dec(regs[1] & 0x7F);
-  uint8_t hour = bcd_to_dec(regs[2] & 0x3F);
-  uint8_t day = bcd_to_dec(regs[4] & 0x3F);
-  uint8_t month = bcd_to_dec(regs[5] & 0x1F);
-  uint16_t year = 2000 + bcd_to_dec(regs[6]);
-
-  struct tm tm_utc = {};
-  tm_utc.tm_sec = sec;
-  tm_utc.tm_min = min;
-  tm_utc.tm_hour = hour;
-  tm_utc.tm_mday = day;
-  tm_utc.tm_mon = month - 1;
-  tm_utc.tm_year = year - 1900;
-  tm_utc.tm_isdst = 0;
-
-  time_t t = timegm_fallback(&tm_utc);
-  if (t <= 0) {
-    return false;
-  }
-  epoch_utc = static_cast<uint32_t>(t);
-  return true;
-}
-
-bool rtc_ds3231_set_epoch(uint32_t epoch_utc) {
-  time_t t = static_cast<time_t>(epoch_utc);
-  struct tm tm_utc = {};
-  if (!gmtime_r(&t, &tm_utc)) {
-    return false;
-  }
-
-  uint8_t regs[7] = {};
-  regs[0] = dec_to_bcd(static_cast<uint8_t>(tm_utc.tm_sec));
-  regs[1] = dec_to_bcd(static_cast<uint8_t>(tm_utc.tm_min));
-  regs[2] = dec_to_bcd(static_cast<uint8_t>(tm_utc.tm_hour));
-  regs[3] = dec_to_bcd(static_cast<uint8_t>(tm_utc.tm_wday + 1));
-  regs[4] = dec_to_bcd(static_cast<uint8_t>(tm_utc.tm_mday));
-  regs[5] = dec_to_bcd(static_cast<uint8_t>(tm_utc.tm_mon + 1));
-  regs[6] = dec_to_bcd(static_cast<uint8_t>((tm_utc.tm_year + 1900) - 2000));
-
-  return write_registers(0x00, regs, sizeof(regs));
-}
--- a/src/sd_logger.cpp
+++ b/src/sd_logger.cpp
@@ -0,0 +1,128 @@
+#include "sd_logger.h"
+#include "config.h"
+#include <SD.h>
+#include <SPI.h>
+#include <time.h>
+
+static bool g_sd_ready = false;
+static SPIClass *g_sd_spi = nullptr;
+
+static const char *fault_text(FaultType fault) {
+  switch (fault) {
+    case FaultType::MeterRead:
+      return "meter";
+    case FaultType::Decode:
+      return "decode";
+    case FaultType::LoraTx:
+      return "loratx";
+    default:
+      return "";
+  }
+}
+
+static bool ensure_dir(const String &path) {
+  if (SD.exists(path)) {
+    return true;
+  }
+  return SD.mkdir(path);
+}
+
+static String format_date_utc(uint32_t ts_utc) {
+  time_t t = static_cast<time_t>(ts_utc);
+  struct tm tm_utc;
+  gmtime_r(&t, &tm_utc);
+  char buf[16];
+  snprintf(buf, sizeof(buf), "%04d-%02d-%02d",
+           tm_utc.tm_year + 1900,
+           tm_utc.tm_mon + 1,
+           tm_utc.tm_mday);
+  return String(buf);
+}
+
+void sd_logger_init() {
+  if (!ENABLE_SD_LOGGING) {
+    g_sd_ready = false;
+    return;
+  }
+  if (!g_sd_spi) {
+    g_sd_spi = new SPIClass(HSPI);
+  }
+  g_sd_spi->begin(PIN_SD_SCK, PIN_SD_MISO, PIN_SD_MOSI, PIN_SD_CS);
+  g_sd_ready = SD.begin(PIN_SD_CS, *g_sd_spi);
+  if (SERIAL_DEBUG_MODE) {
+    if (g_sd_ready) {
+      uint8_t type = SD.cardType();
+      uint64_t size = SD.cardSize();
+      Serial.printf("sd: ok type=%u size=%llu\n", static_cast<unsigned>(type), static_cast<unsigned long long>(size));
+    } else {
+      Serial.println("sd: init failed");
+    }
+  }
+}
+
+bool sd_logger_is_ready() {
+  return g_sd_ready;
+}
+
+void sd_logger_log_sample(const MeterData &data, bool include_error_text) {
+  if (!g_sd_ready || data.ts_utc == 0) {
+    return;
+  }
+
+  String root_dir = "/dd3";
+  if (!ensure_dir(root_dir)) {
+    return;
+  }
+
+  String sender_dir = root_dir + "/" + String(data.device_id);
+  if (!ensure_dir(sender_dir)) {
+    return;
+  }
+
+  String filename = sender_dir + "/" + format_date_utc(data.ts_utc) + ".csv";
+  bool new_file = !SD.exists(filename);
+  File f = SD.open(filename, FILE_APPEND);
+  if (!f) {
+    return;
+  }
+
+  if (new_file) {
+    f.println("ts_utc,p_w,p1_w,p2_w,p3_w,e_kwh,bat_v,bat_pct,rssi,snr,err_m,err_d,err_tx,err_last");
+  }
+
+  f.print(data.ts_utc);
+  f.print(',');
+  f.print(data.total_power_w, 1);
+  f.print(',');
+  f.print(data.phase_power_w[0], 1);
+  f.print(',');
+  f.print(data.phase_power_w[1], 1);
+  f.print(',');
+  f.print(data.phase_power_w[2], 1);
+  f.print(',');
+  f.print(data.energy_total_kwh, 3);
+  f.print(',');
+  f.print(data.battery_voltage_v, 2);
+  f.print(',');
+  f.print(data.battery_percent);
+  f.print(',');
+  f.print(data.link_rssi_dbm);
+  f.print(',');
+  if (isnan(data.link_snr_db)) {
+    f.print("");
+  } else {
+    f.print(data.link_snr_db, 1);
+  }
+  f.print(',');
+  f.print(data.err_meter_read);
+  f.print(',');
+  f.print(data.err_decode);
+  f.print(',');
+  f.print(data.err_lora_tx);
+  f.print(',');
+  if (include_error_text && data.last_error != FaultType::None) {
+    f.print(fault_text(data.last_error));
+  }
+  f.println();
+  f.close();
+}
--- a/src/sd_logger.h
+++ b/src/sd_logger.h
@@ -0,0 +1,7 @@
+#pragma once
+
+#include "data_model.h"
+
+void sd_logger_init();
+bool sd_logger_is_ready();
+void sd_logger_log_sample(const MeterData &data, bool include_error_text);
--- a/src/test_mode.cpp
+++ b/src/test_mode.cpp
@@ -2,9 +2,7 @@

 #ifdef ENABLE_TEST_MODE
 #include "config.h"
-#include "compressor.h"
 #include "lora_transport.h"
-#include "json_codec.h"
 #include "time_manager.h"
 #include "display_ui.h"
 #include "mqtt_client.h"
@@ -14,16 +12,94 @@

 static uint32_t g_last_test_ms = 0;
 static uint16_t g_test_code_counter = 1000;
-static uint32_t g_last_timesync_ms = 0;
+static uint16_t g_test_batch_id = 1;
+static uint16_t g_test_last_acked_batch_id = 0;
 static constexpr uint32_t TEST_SEND_INTERVAL_MS = 30000;
-static constexpr uint32_t TEST_TIMESYNC_OFFSET_MS = 15000;

-void test_sender_loop(uint16_t short_id, const char *device_id) {
-  LoraPacket rx = {};
-  if (lora_receive(rx, 0) && rx.payload_type == PayloadType::TimeSync) {
-    time_handle_timesync_payload(rx.payload, rx.payload_len);
+static void write_u16_be(uint8_t *dst, uint16_t value) {
+  dst[0] = static_cast<uint8_t>((value >> 8) & 0xFF);
+  dst[1] = static_cast<uint8_t>(value & 0xFF);
 }

+static uint16_t read_u16_be(const uint8_t *src) {
+  return static_cast<uint16_t>(src[0] << 8) | static_cast<uint16_t>(src[1]);
+}
+
+static void write_u32_be(uint8_t *dst, uint32_t value) {
+  dst[0] = static_cast<uint8_t>((value >> 24) & 0xFF);
+  dst[1] = static_cast<uint8_t>((value >> 16) & 0xFF);
+  dst[2] = static_cast<uint8_t>((value >> 8) & 0xFF);
+  dst[3] = static_cast<uint8_t>(value & 0xFF);
+}
+
+static uint32_t read_u32_be(const uint8_t *src) {
+  return (static_cast<uint32_t>(src[0]) << 24) |
+      (static_cast<uint32_t>(src[1]) << 16) |
+      (static_cast<uint32_t>(src[2]) << 8) |
+      static_cast<uint32_t>(src[3]);
+}
+
+static uint32_t ack_window_ms() {
+  uint32_t air_ms = lora_airtime_ms(lora_frame_size(LORA_ACK_DOWN_PAYLOAD_LEN));
+  uint32_t window_ms = air_ms + 300;
+  if (window_ms < 1200) {
+    window_ms = 1200;
+  }
+  if (window_ms > 4000) {
+    window_ms = 4000;
+  }
+  return window_ms;
+}
+
+static bool receive_ack_for_batch(uint16_t batch_id, uint8_t &time_valid, uint32_t &ack_epoch, int16_t &rssi_dbm, float &snr_db) {
+  LoraPacket ack_pkt = {};
+  uint32_t window_ms = ack_window_ms();
+  bool got_ack = lora_receive_window(ack_pkt, window_ms);
+  if (!got_ack) {
+    got_ack = lora_receive_window(ack_pkt, window_ms / 2);
+  }
+  if (!got_ack || ack_pkt.msg_kind != LoraMsgKind::AckDown || ack_pkt.payload_len < LORA_ACK_DOWN_PAYLOAD_LEN) {
+    return false;
+  }
+
+  uint16_t ack_id = read_u16_be(&ack_pkt.payload[1]);
+  if (ack_id != batch_id) {
+    return false;
+  }
+
+  time_valid = ack_pkt.payload[0] & 0x01;
+  ack_epoch = read_u32_be(&ack_pkt.payload[3]);
+  rssi_dbm = ack_pkt.rssi_dbm;
+  snr_db = ack_pkt.snr_db;
+  return true;
+}
+
+static void send_test_ack(uint16_t self_short_id, uint16_t batch_id, uint8_t &time_valid, uint32_t &ack_epoch) {
+  ack_epoch = time_get_utc();
+  time_valid = (time_is_synced() && ack_epoch >= MIN_ACCEPTED_EPOCH_UTC) ? 1 : 0;
+  if (!time_valid) {
+    ack_epoch = 0;
+  }
+
+  LoraPacket ack = {};
+  ack.msg_kind = LoraMsgKind::AckDown;
+  ack.device_id_short = self_short_id;
+  ack.payload_len = LORA_ACK_DOWN_PAYLOAD_LEN;
+  ack.payload[0] = time_valid;
+  write_u16_be(&ack.payload[1], batch_id);
+  write_u32_be(&ack.payload[3], ack_epoch);
+
+  uint8_t repeats = ACK_REPEAT_COUNT == 0 ? 1 : ACK_REPEAT_COUNT;
+  for (uint8_t i = 0; i < repeats; ++i) {
+    lora_send(ack);
+    if (i + 1 < repeats && ACK_REPEAT_DELAY_MS > 0) {
+      delay(ACK_REPEAT_DELAY_MS);
+    }
+  }
+  lora_receive_continuous();
+}
+
+void test_sender_loop(uint16_t short_id, const char *device_id) {
  if (millis() - g_last_test_ms < TEST_SEND_INTERVAL_MS) {
    return;
  }
@@ -45,11 +121,13 @@ void test_sender_loop(uint16_t short_id, const char *device_id) {
  uint32_t now_utc = time_get_utc();
  uint32_t ts = now_utc > 0 ? now_utc : millis() / 1000;

-  StaticJsonDocument<128> doc;
+  StaticJsonDocument<192> doc;
  doc["id"] = device_id;
  doc["role"] = "sender";
  doc["test_code"] = code;
  doc["ts"] = ts;
+  doc["batch_id"] = g_test_batch_id;
+  doc["last_acked"] = g_test_last_acked_batch_id;
  char bat_buf[8];
  snprintf(bat_buf, sizeof(bat_buf), "%.2f", data.battery_voltage_v);
  doc["bat_v"] = serialized(bat_buf);
@@ -60,58 +138,71 @@ void test_sender_loop(uint16_t short_id, const char *device_id) {
  data.ts_utc = ts;
  display_set_last_meter(data);

-  uint8_t compressed[LORA_MAX_PAYLOAD];
-  size_t compressed_len = 0;
-  if (!compressBuffer(reinterpret_cast<const uint8_t *>(json.c_str()), json.length(), compressed, sizeof(compressed), compressed_len)) {
+  if (json.length() > LORA_MAX_PAYLOAD) {
    return;
  }

  LoraPacket pkt = {};
-  pkt.protocol_version = PROTOCOL_VERSION;
-  pkt.role = DeviceRole::Sender;
+  pkt.msg_kind = LoraMsgKind::BatchUp;
  pkt.device_id_short = short_id;
-  pkt.payload_type = PayloadType::TestCode;
-  pkt.payload_len = compressed_len;
-  memcpy(pkt.payload, compressed, compressed_len);
-  lora_send(pkt);
+  pkt.payload_len = json.length();
+  memcpy(pkt.payload, json.c_str(), pkt.payload_len);
+  if (!lora_send(pkt)) {
+    return;
+  }
+
+  uint8_t time_valid = 0;
+  uint32_t ack_epoch = 0;
+  int16_t ack_rssi = 0;
+  float ack_snr = 0.0f;
+  if (receive_ack_for_batch(g_test_batch_id, time_valid, ack_epoch, ack_rssi, ack_snr)) {
+    if (time_valid == 1 && ack_epoch >= MIN_ACCEPTED_EPOCH_UTC) {
+      time_set_utc(ack_epoch);
+    }
+    g_test_last_acked_batch_id = g_test_batch_id;
+    g_test_batch_id++;
+    if (SERIAL_DEBUG_MODE) {
+      Serial.printf("test ack: batch=%u time_valid=%u epoch=%lu rssi=%d snr=%.1f\n",
+                    static_cast<unsigned>(g_test_last_acked_batch_id),
+                    static_cast<unsigned>(time_valid),
+                    static_cast<unsigned long>(ack_epoch),
+                    static_cast<int>(ack_rssi),
+                    static_cast<double>(ack_snr));
+    }
+  }
 }

 void test_receiver_loop(SenderStatus *statuses, uint8_t count, uint16_t self_short_id) {
-  if (g_last_timesync_ms == 0) {
-    g_last_timesync_ms = millis() - (TIME_SYNC_INTERVAL_SEC * 1000UL - TEST_TIMESYNC_OFFSET_MS);
-  }
-  if (millis() - g_last_timesync_ms > TIME_SYNC_INTERVAL_SEC * 1000UL) {
-    g_last_timesync_ms = millis();
-    time_send_timesync(self_short_id);
-  }
-
  LoraPacket pkt = {};
  if (!lora_receive(pkt, 0)) {
    return;
  }
-  if (pkt.payload_type != PayloadType::TestCode) {
+  if (pkt.msg_kind != LoraMsgKind::BatchUp) {
    return;
  }

-  uint8_t decompressed[160];
-  size_t decompressed_len = 0;
-  if (!decompressBuffer(pkt.payload, pkt.payload_len, decompressed, sizeof(decompressed) - 1, decompressed_len)) {
+  uint8_t decompressed[192];
+  if (pkt.payload_len >= sizeof(decompressed)) {
    return;
  }
-  if (decompressed_len >= sizeof(decompressed)) {
-    return;
-  }
-  decompressed[decompressed_len] = '\0';
+  memcpy(decompressed, pkt.payload, pkt.payload_len);
+  decompressed[pkt.payload_len] = '\0';

-  StaticJsonDocument<128> doc;
+  StaticJsonDocument<192> doc;
  if (deserializeJson(doc, reinterpret_cast<const char *>(decompressed)) != DeserializationError::Ok) {
    return;
  }

  const char *id = doc["id"] | "";
  const char *code = doc["test_code"] | "";
+  uint16_t batch_id = static_cast<uint16_t>(doc["batch_id"] | 0);
+  uint32_t ts = doc["ts"] | 0;
  float bat_v = doc["bat_v"] | NAN;

+  uint8_t time_valid = 0;
+  uint32_t ack_epoch = 0;
+  send_test_ack(self_short_id, batch_id, time_valid, ack_epoch);
+
  for (uint8_t i = 0; i < count; ++i) {
    if (strncmp(statuses[i].last_data.device_id, id, sizeof(statuses[i].last_data.device_id)) == 0) {
      display_set_test_code_for_sender(i, code);
@@ -119,12 +210,34 @@ void test_receiver_loop(SenderStatus *statuses, uint8_t count, uint16_t self_sho
        statuses[i].last_data.battery_voltage_v = bat_v;
        statuses[i].last_data.battery_percent = battery_percent_from_voltage(bat_v);
      }
+      statuses[i].last_data.link_valid = true;
+      statuses[i].last_data.link_rssi_dbm = pkt.rssi_dbm;
+      statuses[i].last_data.link_snr_db = pkt.snr_db;
+      statuses[i].last_data.ts_utc = ts;
+      statuses[i].last_acked_batch_id = batch_id;
      statuses[i].has_data = true;
      statuses[i].last_update_ts_utc = time_get_utc();
      break;
    }
  }

-  mqtt_publish_test(id, String(reinterpret_cast<const char *>(decompressed)));
+  StaticJsonDocument<256> mqtt_doc;
+  mqtt_doc["id"] = id;
+  mqtt_doc["role"] = "receiver";
+  mqtt_doc["test_code"] = code;
+  mqtt_doc["ts"] = ts;
+  mqtt_doc["batch_id"] = batch_id;
+  mqtt_doc["acked_batch_id"] = batch_id;
+  if (!isnan(bat_v)) {
+    mqtt_doc["bat_v"] = bat_v;
+  }
+  mqtt_doc["rssi"] = pkt.rssi_dbm;
+  mqtt_doc["snr"] = pkt.snr_db;
+  mqtt_doc["time_valid"] = time_valid;
+  mqtt_doc["ack_epoch"] = ack_epoch;
+
+  String mqtt_payload;
+  serializeJson(mqtt_doc, mqtt_payload);
+  mqtt_publish_test(id, mqtt_payload);
 }
 #endif
--- a/src/time_manager.cpp
+++ b/src/time_manager.cpp
@@ -1,12 +1,8 @@
 #include "time_manager.h"
-#include "compressor.h"
-#include "config.h"
-#include "rtc_ds3231.h"
 #include <time.h>

 static bool g_time_synced = false;
 static bool g_tz_set = false;
-static bool g_rtc_present = false;
 static uint32_t g_last_sync_utc = 0;

 static void note_last_sync(uint32_t epoch) {
@@ -55,59 +51,6 @@ void time_set_utc(uint32_t epoch) {
  settimeofday(&tv, nullptr);
  g_time_synced = true;
  note_last_sync(epoch);
-
-  if (g_rtc_present) {
-    rtc_ds3231_set_epoch(epoch);
-  }
-}
-
-bool time_send_timesync(uint16_t device_id_short) {
-  uint32_t epoch = time_get_utc();
-  if (epoch == 0) {
-    return false;
-  }
-
-  char payload_str[32];
-  snprintf(payload_str, sizeof(payload_str), "T:%lu", static_cast<unsigned long>(epoch));
-
-  uint8_t compressed[LORA_MAX_PAYLOAD];
-  size_t compressed_len = 0;
-  if (!compressBuffer(reinterpret_cast<const uint8_t *>(payload_str), strlen(payload_str), compressed, sizeof(compressed), compressed_len)) {
-    return false;
-  }
-
-  LoraPacket pkt = {};
-  pkt.protocol_version = PROTOCOL_VERSION;
-  pkt.role = DeviceRole::Receiver;
-  pkt.device_id_short = device_id_short;
-  pkt.payload_type = PayloadType::TimeSync;
-  pkt.payload_len = compressed_len;
-  memcpy(pkt.payload, compressed, compressed_len);
-  return lora_send(pkt);
-}
-
-bool time_handle_timesync_payload(const uint8_t *payload, size_t len) {
-  uint8_t decompressed[64];
-  size_t decompressed_len = 0;
-  if (!decompressBuffer(payload, len, decompressed, sizeof(decompressed), decompressed_len)) {
-    return false;
-  }
-  if (decompressed_len >= sizeof(decompressed)) {
-    return false;
-  }
-  decompressed[decompressed_len] = '\0';
-
-  if (decompressed_len < 3 || decompressed[0] != 'T' || decompressed[1] != ':') {
-    return false;
-  }
-
-  uint32_t epoch = static_cast<uint32_t>(strtoul(reinterpret_cast<const char *>(decompressed + 2), nullptr, 10));
-  if (epoch == 0) {
-    return false;
-  }
-
-  time_set_utc(epoch);
-  return true;
 }

 void time_get_local_hhmm(char *out, size_t out_len) {
@@ -121,33 +64,6 @@ void time_get_local_hhmm(char *out, size_t out_len) {
  snprintf(out, out_len, "%02d:%02d", timeinfo.tm_hour, timeinfo.tm_min);
 }

-void time_rtc_init() {
-  if (!ENABLE_DS3231) {
-    g_rtc_present = false;
-    return;
-  }
-  g_rtc_present = rtc_ds3231_init();
-}
-
-bool time_try_load_from_rtc() {
-  if (!g_rtc_present) {
-    return false;
-  }
-  if (time_is_synced()) {
-    return true;
-  }
-  uint32_t epoch = 0;
-  if (!rtc_ds3231_read_epoch(epoch) || epoch == 0) {
-    return false;
-  }
-  time_set_utc(epoch);
-  return true;
-}
-
-bool time_rtc_present() {
-  return g_rtc_present;
-}
-
 uint32_t time_get_last_sync_utc() {
  return g_last_sync_utc;
 }
--- a/src/web_server.cpp
+++ b/src/web_server.cpp
@@ -1,17 +1,111 @@
 #include "web_server.h"
 #include <WebServer.h>
 #include "wifi_manager.h"
+#include "config.h"
+#include "sd_logger.h"
+#include "time_manager.h"
+#include "html_util.h"
+#include <SD.h>
+#include <WiFi.h>
+#include <time.h>
+#include <new>
+#include <limits.h>
+#include <math.h>
+#include <stdlib.h>

 static WebServer server(80);
 static const SenderStatus *g_statuses = nullptr;
 static uint8_t g_status_count = 0;
 static WifiMqttConfig g_config;
 static bool g_is_ap = false;
+static String g_web_user;
+static String g_web_pass;
+static const FaultCounters *g_sender_faults = nullptr;
+static const FaultType *g_sender_last_errors = nullptr;
+static MeterData g_last_batch[NUM_SENDERS][METER_BATCH_MAX_SAMPLES];
+static uint8_t g_last_batch_count[NUM_SENDERS] = {};
+
+struct HistoryBin {
+  uint32_t ts;
+  float value;
+  uint32_t count;
+};
+
+enum class HistoryMode : uint8_t {
+  Avg = 0,
+  Max = 1
+};
+
+struct HistoryJob {
+  bool active;
+  bool done;
+  bool error;
+  String error_msg;
+  String device_id;
+  HistoryMode mode;
+  uint32_t start_ts;
+  uint32_t end_ts;
+  uint32_t res_sec;
+  uint32_t bins_count;
+  uint32_t bins_filled;
+  uint16_t day_index;
+  File file;
+  HistoryBin *bins;
+};
+
+static HistoryJob g_history = {};
+static constexpr size_t SD_LIST_MAX_FILES = 200;
+static constexpr size_t SD_DOWNLOAD_MAX_PATH = 160;
+
+static int32_t round_power_w(float value) {
+  if (isnan(value)) {
+    return 0;
+  }
+  long rounded = lroundf(value);
+  if (rounded > INT32_MAX) {
+    return INT32_MAX;
+  }
+  if (rounded < INT32_MIN) {
+    return INT32_MIN;
+  }
+  return static_cast<int32_t>(rounded);
+}
+
+static bool auth_required() {
+  return g_is_ap ? WEB_AUTH_REQUIRE_AP : WEB_AUTH_REQUIRE_STA;
+}
+
+static const char *fault_text(FaultType fault) {
+  switch (fault) {
+    case FaultType::MeterRead:
+      return "meter";
+    case FaultType::Decode:
+      return "decode";
+    case FaultType::LoraTx:
+      return "loratx";
+    default:
+      return "none";
+  }
+}
+
+static bool ensure_auth() {
+  if (!auth_required()) {
+    return true;
+  }
+  const char *user = g_web_user.c_str();
+  const char *pass = g_web_pass.c_str();
+  if (server.authenticate(user, pass)) {
+    return true;
+  }
+  server.requestAuthentication(BASIC_AUTH, "DD3", "Authentication required");
+  return false;
+}

 static String html_header(const String &title) {
+  String safe_title = html_escape(title);
  String h = "<!DOCTYPE html><html><head><meta charset='utf-8'><meta name='viewport' content='width=device-width,initial-scale=1'>";
-  h += "<title>" + title + "</title></head><body>";
-  h += "<h2>" + title + "</h2>";
+  h += "<title>" + safe_title + "</title></head><body>";
+  h += "<h2>" + safe_title + "</h2>";
  return h;
 }

@@ -19,22 +113,328 @@ static String html_footer() {
  return "</body></html>";
 }

+static String format_faults(uint8_t idx) {
+  if (!g_sender_faults || !g_sender_last_errors || idx >= g_status_count) {
+    return "";
+  }
+  String s;
+  s += " faults m:";
+  s += String(g_sender_faults[idx].meter_read_fail);
+  s += " d:";
+  s += String(g_sender_faults[idx].decode_fail);
+  s += " tx:";
+  s += String(g_sender_faults[idx].lora_tx_fail);
+  s += " last:";
+  s += String(static_cast<uint8_t>(g_sender_last_errors[idx]));
+  s += " (" + String(fault_text(g_sender_last_errors[idx])) + ")";
+  return s;
+}
+
+static bool sanitize_sd_download_path(String &path, String &error) {
+  path.trim();
+  if (path.length() == 0) {
+    error = "empty";
+    return false;
+  }
+  if (path.startsWith("dd3/")) {
+    path = "/" + path;
+  }
+  if (path.length() > SD_DOWNLOAD_MAX_PATH) {
+    error = "too_long";
+    return false;
+  }
+  if (!path.startsWith("/dd3/")) {
+    error = "prefix";
+    return false;
+  }
+  if (path.indexOf("..") >= 0) {
+    error = "dotdot";
+    return false;
+  }
+  if (path.indexOf('\\') >= 0) {
+    error = "backslash";
+    return false;
+  }
+  if (path.indexOf("//") >= 0) {
+    error = "repeated_slash";
+    return false;
+  }
+  return true;
+}
+
+static bool checkbox_checked(const char *name) {
+  if (!server.hasArg(name)) {
+    return false;
+  }
+  String val = server.arg(name);
+  return val == "on" || val == "true" || val == "1";
+}
+
+static bool sanitize_history_device_id(const String &input, String &out_device_id) {
+  if (sanitize_device_id(input, out_device_id)) {
+    return true;
+  }
+  if (g_statuses) {
+    for (uint8_t i = 0; i < g_status_count; ++i) {
+      String known = g_statuses[i].last_data.device_id;
+      if (input.equalsIgnoreCase(known) && sanitize_device_id(known, out_device_id)) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+static String sanitize_download_filename(const String &input, bool &clean) {
+  String out;
+  out.reserve(input.length());
+  clean = true;
+  for (size_t i = 0; i < input.length(); ++i) {
+    unsigned char c = static_cast<unsigned char>(input[i]);
+    if (c < 32 || c == 127 || c == '"' || c == '\\' || c == '/') {
+      out += '_';
+      clean = false;
+      continue;
+    }
+    out += static_cast<char>(c);
+  }
+  out.trim();
+  if (out.length() == 0) {
+    out = "download.bin";
+    clean = false;
+  }
+  return out;
+}
+
+static void history_reset() {
+  if (g_history.file) {
+    g_history.file.close();
+  }
+  if (g_history.bins) {
+    delete[] g_history.bins;
+  }
+  g_history = {};
+}
+
+static String history_date_from_epoch(uint32_t ts_utc) {
+  time_t t = static_cast<time_t>(ts_utc);
+  struct tm tm_utc;
+  gmtime_r(&t, &tm_utc);
+  char buf[16];
+  snprintf(buf, sizeof(buf), "%04d-%02d-%02d", tm_utc.tm_year + 1900, tm_utc.tm_mon + 1, tm_utc.tm_mday);
+  return String(buf);
+}
+
+static bool history_open_next_file() {
+  if (!g_history.active || g_history.done || g_history.error) {
+    return false;
+  }
+  if (g_history.file) {
+    g_history.file.close();
+  }
+  uint32_t day_ts = g_history.start_ts + static_cast<uint32_t>(g_history.day_index) * 86400UL;
+  if (day_ts > g_history.end_ts) {
+    g_history.done = true;
+    return false;
+  }
+  String path = String("/dd3/") + g_history.device_id + "/" + history_date_from_epoch(day_ts) + ".csv";
+  g_history.file = SD.open(path.c_str(), FILE_READ);
+  g_history.day_index++;
+  return true;
+}
+
+static bool history_parse_line(const char *line, uint32_t &ts_out, float &p_out) {
+  if (!line || line[0] < '0' || line[0] > '9') {
+    return false;
+  }
+  const char *comma = strchr(line, ',');
+  if (!comma) {
+    return false;
+  }
+  char ts_buf[16];
+  size_t ts_len = static_cast<size_t>(comma - line);
+  if (ts_len >= sizeof(ts_buf)) {
+    return false;
+  }
+  memcpy(ts_buf, line, ts_len);
+  ts_buf[ts_len] = '\0';
+  char *end = nullptr;
+  uint32_t ts = static_cast<uint32_t>(strtoul(ts_buf, &end, 10));
+  if (end == ts_buf) {
+    return false;
+  }
+  const char *p_start = comma + 1;
+  const char *p_end = strchr(p_start, ',');
+  char p_buf[16];
+  size_t p_len = p_end ? static_cast<size_t>(p_end - p_start) : strlen(p_start);
+  if (p_len >= sizeof(p_buf)) {
+    return false;
+  }
+  memcpy(p_buf, p_start, p_len);
+  p_buf[p_len] = '\0';
+  char *endp = nullptr;
+  float p = strtof(p_buf, &endp);
+  if (endp == p_buf) {
+    return false;
+  }
+  ts_out = ts;
+  p_out = p;
+  return true;
+}
+
+static void history_tick() {
+  if (!g_history.active || g_history.done || g_history.error) {
+    return;
+  }
+  if (!sd_logger_is_ready()) {
+    g_history.error = true;
+    g_history.error_msg = "sd_not_ready";
+    return;
+  }
+
+  uint32_t start_ms = millis();
+  while (millis() - start_ms < SD_HISTORY_TIME_BUDGET_MS) {
+    if (!g_history.file) {
+      if (!history_open_next_file()) {
+        if (g_history.done) {
+          g_history.active = false;
+        }
+        return;
+      }
+    }
+    if (!g_history.file.available()) {
+      g_history.file.close();
+      continue;
+    }
+
+    char line[160];
+    size_t n = g_history.file.readBytesUntil('\n', line, sizeof(line) - 1);
+    line[n] = '\0';
+    if (n == 0) {
+      continue;
+    }
+    uint32_t ts = 0;
+    float p = 0.0f;
+    if (!history_parse_line(line, ts, p)) {
+      continue;
+    }
+    if (ts < g_history.start_ts || ts > g_history.end_ts) {
+      continue;
+    }
+    uint32_t idx = (ts - g_history.start_ts) / g_history.res_sec;
+    if (idx >= g_history.bins_count) {
+      continue;
+    }
+    HistoryBin &bin = g_history.bins[idx];
+    if (bin.count == 0) {
+      bin.ts = g_history.start_ts + idx * g_history.res_sec;
+      bin.value = p;
+      bin.count = 1;
+      g_history.bins_filled++;
+    } else if (g_history.mode == HistoryMode::Avg) {
+      bin.value += p;
+      bin.count++;
+    } else {
+      if (p > bin.value) {
+        bin.value = p;
+      }
+      bin.count++;
+    }
+  }
+}
+
 static String render_sender_block(const SenderStatus &status) {
  String s;
  s += "<div style='margin-bottom:10px;padding:6px;border:1px solid #ccc'>";
-  s += "<strong>" + String(status.last_data.device_id) + "</strong><br>";
+  uint8_t idx = 0;
+  if (g_statuses) {
+    for (uint8_t i = 0; i < g_status_count; ++i) {
+      if (&g_statuses[i] == &status) {
+        idx = i;
+        break;
+      }
+    }
+  }
+  String device_id = status.last_data.device_id;
+  String device_id_safe = html_escape(device_id);
+  String device_id_url = url_encode_component(device_id);
+  s += "<strong><a href='/sender/" + device_id_url + "' target='_blank' rel='noopener noreferrer'>" + device_id_safe + "</a></strong>";
+  if (status.has_data && status.last_data.link_valid) {
+    s += " RSSI:" + String(status.last_data.link_rssi_dbm) + " SNR:" + String(status.last_data.link_snr_db, 1);
+  }
+  if (status.has_data) {
+    s += " ack:" + String(status.last_acked_batch_id);
+    s += " err_tx:" + String(status.last_data.err_lora_tx);
+    s += " err_last:" + String(static_cast<uint8_t>(status.last_data.last_error));
+    s += " (" + String(fault_text(status.last_data.last_error)) + ")";
+    s += " rx_reject:" + String(status.last_data.rx_reject_reason);
+    s += " (" + String(rx_reject_reason_text(static_cast<RxRejectReason>(status.last_data.rx_reject_reason))) + ")";
+  }
+  s += format_faults(idx);
+  s += "<br>";
  if (!status.has_data) {
    s += "No data";
  } else {
-    s += "Energy: " + String(status.last_data.energy_total_kwh, 3) + " kWh<br>";
-    s += "Power: " + String(status.last_data.total_power_w, 1) + " W<br>";
-    s += "Battery: " + String(status.last_data.battery_voltage_v, 2) + " V (" + String(status.last_data.battery_percent) + ")";
+    if (status.last_data.energy_multi) {
+      s += "Energy1: " + String(status.last_data.energy_kwh_int[0]) + " kWh<br>";
+      s += "Energy2: " + String(status.last_data.energy_kwh_int[1]) + " kWh<br>";
+      if (status.last_data.energy_meter_count >= 3) {
+        s += "Energy3: " + String(status.last_data.energy_kwh_int[2]) + " kWh<br>";
+      }
+    } else {
+      s += "Energy: " + String(status.last_data.energy_total_kwh, 2) + " kWh<br>";
+      s += "Power: " + String(round_power_w(status.last_data.total_power_w)) + " W<br>";
+      s += "P1/P2/P3: " + String(round_power_w(status.last_data.phase_power_w[0])) + " / " +
+           String(round_power_w(status.last_data.phase_power_w[1])) + " / " +
+           String(round_power_w(status.last_data.phase_power_w[2])) + " W<br>";
+    }
+    s += "Battery: " + String(status.last_data.battery_percent) + "% (" + String(status.last_data.battery_voltage_v, 2) + " V)";
  }
  s += "</div>";
  return s;
 }

+static void append_sd_listing(String &html, const String &dir_path, uint8_t depth, size_t &count) {
+  if (count >= SD_LIST_MAX_FILES || depth > 4) {
+    return;
+  }
+  File dir = SD.open(dir_path.c_str());
+  if (!dir || !dir.isDirectory()) {
+    return;
+  }
+  File entry = dir.openNextFile();
+  while (entry && count < SD_LIST_MAX_FILES) {
+    String name = entry.name();
+    String full_path = name;
+    if (!full_path.startsWith(dir_path)) {
+      if (!dir_path.endsWith("/")) {
+        full_path = dir_path + "/" + name;
+      } else {
+        full_path = dir_path + name;
+      }
+    }
+    if (entry.isDirectory()) {
+      html += "<li><strong>" + html_escape(full_path) + "/</strong></li>";
+      append_sd_listing(html, full_path, depth + 1, count);
+    } else {
+      String href = full_path;
+      if (!href.startsWith("/")) {
+        href = "/" + href;
+      }
+      String href_enc = url_encode_component(href);
+      html += "<li><a href='/sd/download?path=" + href_enc + "' target='_blank' rel='noopener noreferrer'>" + html_escape(full_path) + "</a>";
+      html += " (" + String(entry.size()) + " bytes)</li>";
+      count++;
+    }
+    entry = dir.openNextFile();
+  }
+  dir.close();
+}
+
 static void handle_root() {
+  if (!ensure_auth()) {
+    return;
+  }
  String html = html_header("DD3 Bridge Status");
  html += g_is_ap ? "<p>Mode: AP</p>" : "<p>Mode: STA</p>";

@@ -44,22 +444,45 @@ static void handle_root() {
    }
  }

+  if (sd_logger_is_ready()) {
+    html += "<h3>SD Files</h3><ul>";
+    size_t count = 0;
+    append_sd_listing(html, "/dd3", 0, count);
+    if (count >= SD_LIST_MAX_FILES) {
+      html += "<li>Listing truncated...</li>";
+    }
+    html += "</ul>";
+  } else {
+    html += "<p>SD: not ready</p>";
+  }
+
  html += "<p><a href='/wifi'>Configure WiFi/MQTT/NTP</a></p>";
+  html += "<p><a href='/manual'>Manual</a></p>";
  html += html_footer();
  server.send(200, "text/html", html);
 }

 static void handle_wifi_get() {
+  if (!ensure_auth()) {
+    return;
+  }
  String html = html_header("WiFi/MQTT Config");
  html += "<form method='POST' action='/wifi'>";
-  html += "SSID: <input name='ssid' value='" + g_config.ssid + "'><br>";
-  html += "Password: <input name='pass' type='password' value='" + g_config.password + "'><br>";
-  html += "MQTT Host: <input name='mqhost' value='" + g_config.mqtt_host + "'><br>";
+  html += "SSID: <input name='ssid' value='" + html_escape(g_config.ssid) + "'><br>";
+  html += "Password: <input name='pass' type='password'> ";
+  html += "<label><input type='checkbox' name='clear_wifi_pass'> Clear password</label><br>";
+  html += "MQTT Host: <input name='mqhost' value='" + html_escape(g_config.mqtt_host) + "'><br>";
  html += "MQTT Port: <input name='mqport' value='" + String(g_config.mqtt_port) + "'><br>";
-  html += "MQTT User: <input name='mquser' value='" + g_config.mqtt_user + "'><br>";
-  html += "MQTT Pass: <input name='mqpass' type='password' value='" + g_config.mqtt_pass + "'><br>";
-  html += "NTP Server 1: <input name='ntp1' value='" + g_config.ntp_server_1 + "'><br>";
-  html += "NTP Server 2: <input name='ntp2' value='" + g_config.ntp_server_2 + "'><br>";
+  html += "MQTT User: <input name='mquser' value='" + html_escape(g_config.mqtt_user) + "'><br>";
+  html += "MQTT Pass: <input name='mqpass' type='password'> ";
+  html += "<label><input type='checkbox' name='clear_mqtt_pass'> Clear password</label><br>";
+  html += "NTP Server 1: <input name='ntp1' value='" + html_escape(g_config.ntp_server_1) + "'><br>";
+  html += "NTP Server 2: <input name='ntp2' value='" + html_escape(g_config.ntp_server_2) + "'><br>";
+  html += "<hr>";
+  html += "Web UI User: <input name='webuser' value='" + html_escape(g_config.web_user) + "'><br>";
+  html += "Web UI Pass: <input name='webpass' type='password'> ";
+  html += "<label><input type='checkbox' name='clear_web_pass'> Clear password</label><br>";
+  html += "<div style='font-size:12px;color:#666;'>Leaving password blank keeps the existing one.</div>";
  html += "<button type='submit'>Save</button>";
  html += "</form>";
  html += html_footer();
@@ -67,15 +490,38 @@ static void handle_wifi_get() {
 }

 static void handle_wifi_post() {
-  WifiMqttConfig cfg;
-  cfg.ntp_server_1 = "pool.ntp.org";
-  cfg.ntp_server_2 = "time.nist.gov";
+  if (!ensure_auth()) {
+    return;
+  }
+  WifiMqttConfig cfg = g_config;
+  cfg.ntp_server_1 = g_config.ntp_server_1.length() > 0 ? g_config.ntp_server_1 : "pool.ntp.org";
+  cfg.ntp_server_2 = g_config.ntp_server_2.length() > 0 ? g_config.ntp_server_2 : "time.nist.gov";
  cfg.ssid = server.arg("ssid");
-  cfg.password = server.arg("pass");
+  String wifi_pass = server.arg("pass");
+  if (checkbox_checked("clear_wifi_pass")) {
+    cfg.password = "";
+  } else if (wifi_pass.length() > 0) {
+    cfg.password = wifi_pass;
+  }
  cfg.mqtt_host = server.arg("mqhost");
  cfg.mqtt_port = static_cast<uint16_t>(server.arg("mqport").toInt());
  cfg.mqtt_user = server.arg("mquser");
-  cfg.mqtt_pass = server.arg("mqpass");
+  String mqtt_pass = server.arg("mqpass");
+  if (checkbox_checked("clear_mqtt_pass")) {
+    cfg.mqtt_pass = "";
+  } else if (mqtt_pass.length() > 0) {
+    cfg.mqtt_pass = mqtt_pass;
+  }
+  String web_user = server.arg("webuser");
+  if (web_user.length() > 0) {
+    cfg.web_user = web_user;
+  }
+  String web_pass = server.arg("webpass");
+  if (checkbox_checked("clear_web_pass")) {
+    cfg.web_pass = "";
+  } else if (web_pass.length() > 0) {
+    cfg.web_pass = web_pass;
+  }
  if (server.arg("ntp1").length() > 0) {
    cfg.ntp_server_1 = server.arg("ntp1");
  }
@@ -83,6 +529,9 @@ static void handle_wifi_post() {
    cfg.ntp_server_2 = server.arg("ntp2");
  }
  cfg.valid = true;
+  g_config = cfg;
+  g_web_user = cfg.web_user;
+  g_web_pass = cfg.web_pass;
  wifi_save_config(cfg);
  server.send(200, "text/html", "<html><body>Saved. Rebooting...</body></html>");
  delay(1000);
@@ -90,16 +539,107 @@ static void handle_wifi_post() {
 }

 static void handle_sender() {
+  if (!ensure_auth()) {
+    return;
+  }
  if (!g_statuses) {
    server.send(404, "text/plain", "No senders");
    return;
  }
  String uri = server.uri();
  String device_id = uri.substring(String("/sender/").length());
+  String device_id_url = url_encode_component(device_id);
  for (uint8_t i = 0; i < g_status_count; ++i) {
    if (device_id.equalsIgnoreCase(g_statuses[i].last_data.device_id)) {
      String html = html_header("Sender " + device_id);
      html += render_sender_block(g_statuses[i]);
+      html += "<h3>History (Power)</h3>";
+      html += "<div>";
+      html += "Days: <input id='hist_days' type='number' min='1' max='" + String(SD_HISTORY_MAX_DAYS) + "' value='7' style='width:60px'> ";
+      html += "Res(min): <input id='hist_res' type='number' min='" + String(SD_HISTORY_MIN_RES_MIN) + "' value='5' style='width:60px'> ";
+      html += "<select id='hist_mode'><option value='avg'>avg</option><option value='max'>max</option></select> ";
+      html += "<button onclick='drawHistory()'>Draw</button>";
+      html += "<div id='hist_status' style='font-size:12px;margin-top:4px;color:#666;'></div>";
+      html += "<canvas id='hist_canvas' width='320' height='140' style='width:100%;max-width:520px;border:1px solid #ccc;margin-top:6px;'></canvas>";
+      html += "</div>";
+      html += "<script>";
+      html += "const deviceId='" + device_id_url + "';";
+      html += "let histTimer=null;";
+      html += "function histStatus(msg){document.getElementById('hist_status').textContent=msg;}";
+      html += "function drawHistory(){";
+      html += "const days=document.getElementById('hist_days').value;";
+      html += "const res=document.getElementById('hist_res').value;";
+      html += "const mode=document.getElementById('hist_mode').value;";
+      html += "histStatus('Starting...');";
+      html += "fetch(`/history/start?device_id=${deviceId}&days=${days}&res=${res}&mode=${mode}`)";
+      html += ".then(r=>r.json()).then(j=>{";
+      html += "if(!j.ok){histStatus('Error: '+(j.error||'failed'));return;}";
+      html += "if(histTimer){clearInterval(histTimer);}";
+      html += "histTimer=setInterval(()=>fetchHistory(),1000);";
+      html += "fetchHistory();";
+      html += "});";
+      html += "}";
+      html += "function fetchHistory(){";
+      html += "fetch(`/history/data?device_id=${deviceId}`).then(r=>r.json()).then(j=>{";
+      html += "if(!j.ready){histStatus(j.error?('Error: '+j.error):('Processing... '+(j.progress||0)+'%'));return;}";
+      html += "if(histTimer){clearInterval(histTimer);histTimer=null;}";
+      html += "renderChart(j.series);";
+      html += "histStatus('Done');";
+      html += "});";
+      html += "}";
+      html += "function renderChart(series){";
+      html += "const canvas=document.getElementById('hist_canvas');";
+      html += "const w=canvas.clientWidth;const h=canvas.clientHeight;";
+      html += "canvas.width=w;canvas.height=h;";
+      html += "const ctx=canvas.getContext('2d');";
+      html += "ctx.clearRect(0,0,w,h);";
+      html += "if(!series||series.length===0){ctx.fillText('No data',10,20);return;}";
+      html += "let min=Infinity,max=-Infinity;";
+      html += "for(const p of series){if(p[1]===null)continue; if(p[1]<min)min=p[1]; if(p[1]>max)max=p[1];}";
+      html += "if(!isFinite(min)||!isFinite(max)){ctx.fillText('No data',10,20);return;}";
+      html += "if(min===max){min=0;}";
+      html += "ctx.strokeStyle='#333';ctx.lineWidth=1;ctx.beginPath();";
+      html += "let first=true;";
+      html += "for(let i=0;i<series.length;i++){";
+      html += "const v=series[i][1];";
+      html += "if(v===null)continue;";
+      html += "const x=(i/(series.length-1))* (w-2) + 1;";
+      html += "const y=h-2-((v-min)/(max-min))*(h-4);";
+      html += "if(first){ctx.moveTo(x,y);first=false;} else {ctx.lineTo(x,y);} }";
+      html += "ctx.stroke();";
+      html += "ctx.fillStyle='#666';ctx.fillText(min.toFixed(0)+'W',4,h-4);";
+      html += "ctx.fillText(max.toFixed(0)+'W',4,12);";
+      html += "}";
+      html += "</script>";
+      if (g_last_batch_count[i] > 0) {
+        html += "<h3>Last batch (" + String(g_last_batch_count[i]) + " samples)</h3>";
+        html += "<table border='1' cellspacing='0' cellpadding='3'>";
+        html += "<tr><th>#</th><th>ts</th><th>energy1_kwh</th><th>energy2_kwh</th><th>energy3_kwh</th><th>p_w</th><th>p1_w</th><th>p2_w</th><th>p3_w</th>";
+        html += "<th>bat_v</th><th>bat_pct</th><th>rssi</th><th>snr</th><th>err_tx</th><th>err_last</th><th>rx_reject</th></tr>";
+        for (uint8_t r = 0; r < g_last_batch_count[i]; ++r) {
+          const MeterData &d = g_last_batch[i][r];
+          html += "<tr>";
+          html += "<td>" + String(r) + "</td>";
+          html += "<td>" + String(d.ts_utc) + "</td>";
+          html += "<td>" + String(d.energy_kwh_int[0]) + "</td>";
+          html += "<td>" + String(d.energy_kwh_int[1]) + "</td>";
+          html += "<td>" + String(d.energy_kwh_int[2]) + "</td>";
+          html += "<td>" + String(round_power_w(d.total_power_w)) + "</td>";
+          html += "<td>" + String(round_power_w(d.phase_power_w[0])) + "</td>";
+          html += "<td>" + String(round_power_w(d.phase_power_w[1])) + "</td>";
+          html += "<td>" + String(round_power_w(d.phase_power_w[2])) + "</td>";
+          html += "<td>" + String(d.battery_voltage_v, 2) + "</td>";
+          html += "<td>" + String(d.battery_percent) + "</td>";
+          html += "<td>" + String(d.link_rssi_dbm) + "</td>";
+          html += "<td>" + String(d.link_snr_db, 1) + "</td>";
+          html += "<td>" + String(d.err_lora_tx) + "</td>";
+          html += "<td>" + String(static_cast<uint8_t>(d.last_error)) + " (" + String(fault_text(d.last_error)) + ")</td>";
+          html += "<td>" + String(d.rx_reject_reason) + " (" +
+                  String(rx_reject_reason_text(static_cast<RxRejectReason>(d.rx_reject_reason))) + ")</td>";
+          html += "</tr>";
+        }
+        html += "</table>";
+      }
      html += html_footer();
      server.send(200, "text/html", html);
      return;
@@ -108,8 +648,217 @@ static void handle_sender() {
  server.send(404, "text/plain", "Not found");
 }

+static void handle_manual() {
+  if (!ensure_auth()) {
+    return;
+  }
+  String html = html_header("DD3 Manual");
+  html += "<ul>";
+  html += "<li>Energy: total kWh since meter start.</li>";
+  html += "<li>Power: total active power in W.</li>";
+  html += "<li>P1/P2/P3: phase power in W.</li>";
+  html += "<li>Battery: percent with voltage in V.</li>";
+  html += "<li>RSSI/SNR: LoRa link quality from last packet.</li>";
+  html += "<li>err_tx: sender-side LoRa TX error counter.</li>";
+  html += "<li>err_last: last error code (0=None, 1=MeterRead, 2=Decode, 3=LoraTx).</li>";
+  html += "<li>rx_reject: last RX reject reason (0=None, 1=crc_fail, 2=invalid_msg_kind, 3=length_mismatch, 4=device_id_mismatch, 5=batch_id_mismatch).</li>";
+  html += "<li>faults m/d/tx: receiver-side counters (meter read fails, decode fails, LoRa TX fails).</li>";
+  html += "<li>faults last: last receiver-side error code (same mapping as err_last).</li>";
+  html += "</ul>";
+  html += html_footer();
+  server.send(200, "text/html", html);
+}
+
+static void handle_history_start() {
+  if (!ensure_auth()) {
+    return;
+  }
+  if (!sd_logger_is_ready()) {
+    server.send(200, "application/json", "{\"ok\":false,\"error\":\"sd_not_ready\"}");
+    return;
+  }
+  if (!time_is_synced()) {
+    server.send(200, "application/json", "{\"ok\":false,\"error\":\"time_not_synced\"}");
+    return;
+  }
+  String device_id_arg = server.arg("device_id");
+  String device_id;
+  if (!sanitize_history_device_id(device_id_arg, device_id)) {
+    server.send(200, "application/json", "{\"ok\":false,\"error\":\"bad_device_id\"}");
+    return;
+  }
+  uint16_t days = static_cast<uint16_t>(server.arg("days").toInt());
+  uint16_t res_min = static_cast<uint16_t>(server.arg("res").toInt());
+  String mode_str = server.arg("mode");
+  if (device_id.length() == 0 || days == 0 || res_min == 0) {
+    server.send(200, "application/json", "{\"ok\":false,\"error\":\"bad_params\"}");
+    return;
+  }
+  if (days > SD_HISTORY_MAX_DAYS) {
+    days = SD_HISTORY_MAX_DAYS;
+  }
+  if (res_min < SD_HISTORY_MIN_RES_MIN) {
+    res_min = SD_HISTORY_MIN_RES_MIN;
+  }
+  uint32_t bins = (static_cast<uint32_t>(days) * 24UL * 60UL) / res_min;
+  if (bins == 0 || bins > SD_HISTORY_MAX_BINS) {
+    String resp = String("{\"ok\":false,\"error\":\"too_many_bins\",\"max_bins\":") + SD_HISTORY_MAX_BINS + "}";
+    server.send(200, "application/json", resp);
+    return;
+  }
+
+  history_reset();
+  g_history.active = true;
+  g_history.done = false;
+  g_history.error = false;
+  g_history.device_id = device_id;
+  g_history.mode = (mode_str == "max") ? HistoryMode::Max : HistoryMode::Avg;
+  g_history.res_sec = static_cast<uint32_t>(res_min) * 60UL;
+  g_history.bins_count = bins;
+  g_history.day_index = 0;
+  g_history.bins = new (std::nothrow) HistoryBin[bins];
+  if (!g_history.bins) {
+    g_history.error = true;
+    g_history.error_msg = "oom";
+    server.send(200, "application/json", "{\"ok\":false,\"error\":\"oom\"}");
+    return;
+  }
+  for (uint32_t i = 0; i < bins; ++i) {
+    g_history.bins[i] = {};
+  }
+  g_history.end_ts = time_get_utc();
+  uint32_t span = static_cast<uint32_t>(days) * 86400UL;
+  g_history.start_ts = g_history.end_ts > span ? (g_history.end_ts - span) : 0;
+  if (g_history.res_sec > 0) {
+    g_history.start_ts = (g_history.start_ts / g_history.res_sec) * g_history.res_sec;
+  }
+
+  String resp = String("{\"ok\":true,\"bins\":") + bins + "}";
+  server.send(200, "application/json", resp);
+}
+
+static void handle_history_data() {
+  if (!ensure_auth()) {
+    return;
+  }
+  String device_id_arg = server.arg("device_id");
+  String device_id;
+  if (!sanitize_history_device_id(device_id_arg, device_id)) {
+    server.send(200, "application/json", "{\"ready\":false,\"error\":\"bad_device_id\"}");
+    return;
+  }
+  if (!g_history.bins || device_id.length() == 0 || device_id != g_history.device_id) {
+    server.send(200, "application/json", "{\"ready\":false,\"error\":\"no_job\"}");
+    return;
+  }
+  if (g_history.error) {
+    String resp = String("{\"ready\":false,\"error\":\"") + g_history.error_msg + "\"}";
+    server.send(200, "application/json", resp);
+    return;
+  }
+  if (g_history.active && !g_history.done) {
+    uint32_t progress = g_history.bins_count == 0 ? 0 : (g_history.bins_filled * 100UL / g_history.bins_count);
+    String resp = String("{\"ready\":false,\"progress\":") + progress + "}";
+    server.send(200, "application/json", resp);
+    return;
+  }
+
+  server.setContentLength(CONTENT_LENGTH_UNKNOWN);
+  server.send(200, "application/json", "");
+  server.sendContent("{\"ready\":true,\"series\":[");
+  bool first = true;
+  for (uint32_t i = 0; i < g_history.bins_count; ++i) {
+    const HistoryBin &bin = g_history.bins[i];
+    if (!first) {
+      server.sendContent(",");
+    }
+    first = false;
+    float value = NAN;
+    if (bin.count > 0) {
+      value = (g_history.mode == HistoryMode::Avg) ? (bin.value / static_cast<float>(bin.count)) : bin.value;
+    }
+    if (bin.count == 0) {
+      server.sendContent(String("[") + bin.ts + ",null]");
+    } else {
+      int32_t rounded = round_power_w(value);
+      server.sendContent(String("[") + bin.ts + "," + String(rounded) + "]");
+    }
+  }
+  server.sendContent("]}");
+}
+
+static void handle_sd_download() {
+  if (!ensure_auth()) {
+    return;
+  }
+  if (!sd_logger_is_ready()) {
+    server.send(404, "text/plain", "SD not ready");
+    return;
+  }
+  String path = server.arg("path");
+  String error;
+  if (!sanitize_sd_download_path(path, error)) {
+    if (SERIAL_DEBUG_MODE) {
+      Serial.printf("sd: reject path '%s' reason=%s\n", path.c_str(), error.c_str());
+    }
+    server.send(400, "text/plain", "Invalid path");
+    return;
+  }
+  File f = SD.open(path.c_str(), FILE_READ);
+  if (!f) {
+    server.send(404, "text/plain", "Not found");
+    return;
+  }
+  size_t size = f.size();
+  String filename = path.substring(path.lastIndexOf('/') + 1);
+  bool name_clean = true;
+  (void)name_clean;
+  String safe_name = sanitize_download_filename(filename, name_clean);
+  String cd = "attachment; filename=\"" + safe_name + "\"; filename*=UTF-8''" + url_encode_component(safe_name);
+  server.sendHeader("Content-Disposition", cd);
+  server.setContentLength(size);
+  const char *content_type = "application/octet-stream";
+  if (filename.endsWith(".csv")) {
+    content_type = "text/csv";
+  } else if (filename.endsWith(".txt")) {
+    content_type = "text/plain";
+  }
+  server.send(200, content_type, "");
+  WiFiClient client = server.client();
+  uint8_t buf[512];
+  while (f.available()) {
+    size_t n = f.read(buf, sizeof(buf));
+    if (n == 0) {
+      break;
+    }
+    client.write(buf, n);
+    delay(0);
+  }
+  f.close();
+}
+
 void web_server_set_config(const WifiMqttConfig &config) {
  g_config = config;
+  g_web_user = config.web_user;
+  g_web_pass = config.web_pass;
+}
+
+void web_server_set_sender_faults(const FaultCounters *faults, const FaultType *last_errors) {
+  g_sender_faults = faults;
+  g_sender_last_errors = last_errors;
+}
+
+void web_server_set_last_batch(uint8_t sender_index, const MeterData *samples, size_t count) {
+  if (!samples || sender_index >= NUM_SENDERS) {
+    return;
+  }
+  if (count > METER_BATCH_MAX_SAMPLES) {
+    count = METER_BATCH_MAX_SAMPLES;
+  }
+  g_last_batch_count[sender_index] = static_cast<uint8_t>(count);
+  for (size_t i = 0; i < count; ++i) {
+    g_last_batch[sender_index][i] = samples[i];
+  }
 }

 void web_server_begin_ap(const SenderStatus *statuses, uint8_t count) {
@@ -118,6 +867,10 @@ void web_server_begin_ap(const SenderStatus *statuses, uint8_t count) {
  g_is_ap = true;

  server.on("/", handle_root);
+  server.on("/manual", handle_manual);
+  server.on("/history/start", handle_history_start);
+  server.on("/history/data", handle_history_data);
+  server.on("/sd/download", handle_sd_download);
  server.on("/wifi", HTTP_GET, handle_wifi_get);
  server.on("/wifi", HTTP_POST, handle_wifi_post);
  server.on("/sender/", handle_sender);
@@ -137,7 +890,11 @@ void web_server_begin_sta(const SenderStatus *statuses, uint8_t count) {
  g_is_ap = false;

  server.on("/", handle_root);
+  server.on("/manual", handle_manual);
  server.on("/sender/", handle_sender);
+  server.on("/history/start", handle_history_start);
+  server.on("/history/data", handle_history_data);
+  server.on("/sd/download", handle_sd_download);
  server.on("/wifi", HTTP_GET, handle_wifi_get);
  server.on("/wifi", HTTP_POST, handle_wifi_post);
  server.onNotFound([]() {
@@ -151,5 +908,6 @@ void web_server_begin_sta(const SenderStatus *statuses, uint8_t count) {
 }

 void web_server_loop() {
+  history_tick();
  server.handleClient();
 }
--- a/src/wifi_manager.cpp
+++ b/src/wifi_manager.cpp
@@ -1,4 +1,5 @@
 #include "wifi_manager.h"
+#include "config.h"
 #include <WiFi.h>
 #include <esp_wifi.h>

@@ -10,9 +11,6 @@ void wifi_manager_init() {

 bool wifi_load_config(WifiMqttConfig &config) {
  config.valid = prefs.getBool("valid", false);
-  if (!config.valid) {
-    return false;
-  }
  config.ssid = prefs.getString("ssid", "");
  config.password = prefs.getString("pass", "");
  config.mqtt_host = prefs.getString("mqhost", "");
@@ -21,6 +19,11 @@ bool wifi_load_config(WifiMqttConfig &config) {
  config.mqtt_pass = prefs.getString("mqpass", "");
  config.ntp_server_1 = prefs.getString("ntp1", "pool.ntp.org");
  config.ntp_server_2 = prefs.getString("ntp2", "time.nist.gov");
+  config.web_user = prefs.getString("webuser", WEB_AUTH_DEFAULT_USER);
+  config.web_pass = prefs.getString("webpass", WEB_AUTH_DEFAULT_PASS);
+  if (!config.valid) {
+    return false;
+  }
  return config.ssid.length() > 0 && config.mqtt_host.length() > 0;
 }

@@ -34,6 +37,8 @@ bool wifi_save_config(const WifiMqttConfig &config) {
  prefs.putString("mqpass", config.mqtt_pass);
  prefs.putString("ntp1", config.ntp_server_1);
  prefs.putString("ntp2", config.ntp_server_2);
+  prefs.putString("webuser", config.web_user);
+  prefs.putString("webpass", config.web_pass);
  return true;
 }

--- a/test/test_html_escape/test_html_escape.cpp
+++ b/test/test_html_escape/test_html_escape.cpp
@@ -0,0 +1,37 @@
+#include <Arduino.h>
+#include <unity.h>
+#include "html_util.h"
+
+static void test_html_escape_basic() {
+  TEST_ASSERT_EQUAL_STRING("", html_escape("").c_str());
+  TEST_ASSERT_EQUAL_STRING("plain", html_escape("plain").c_str());
+  TEST_ASSERT_EQUAL_STRING("a&amp;b", html_escape("a&b").c_str());
+  TEST_ASSERT_EQUAL_STRING("&lt;tag&gt;", html_escape("<tag>").c_str());
+  TEST_ASSERT_EQUAL_STRING("&quot;hi&quot;", html_escape("\"hi\"").c_str());
+  TEST_ASSERT_EQUAL_STRING("it&#39;s", html_escape("it's").c_str());
+  TEST_ASSERT_EQUAL_STRING("&amp;&lt;&gt;&quot;&#39;", html_escape("&<>\"'").c_str());
+}
+
+static void test_sanitize_device_id() {
+  String out;
+  TEST_ASSERT_TRUE(sanitize_device_id("F19C", out));
+  TEST_ASSERT_EQUAL_STRING("dd3-F19C", out.c_str());
+  TEST_ASSERT_TRUE(sanitize_device_id("dd3-f19c", out));
+  TEST_ASSERT_EQUAL_STRING("dd3-F19C", out.c_str());
+  TEST_ASSERT_FALSE(sanitize_device_id("F19G", out));
+  TEST_ASSERT_FALSE(sanitize_device_id("dd3-12", out));
+  TEST_ASSERT_FALSE(sanitize_device_id("dd3-12345", out));
+  TEST_ASSERT_FALSE(sanitize_device_id("../F19C", out));
+  TEST_ASSERT_FALSE(sanitize_device_id("dd3-%2f", out));
+  TEST_ASSERT_FALSE(sanitize_device_id("dd3-12/3", out));
+  TEST_ASSERT_FALSE(sanitize_device_id("dd3-12\\3", out));
+}
+
+void setup() {
+  UNITY_BEGIN();
+  RUN_TEST(test_html_escape_basic);
+  RUN_TEST(test_sanitize_device_id);
+  UNITY_END();
+}
+
+void loop() {}
Author	SHA1	Message	Date
acidburns	eb80f49046	test: align test mode with ACK/time flow and expose ack metrics	2026-02-04 20:12:02 +01:00
acidburns	31a3eea5dd	docs: rewrite README for current multi-meter behavior	2026-02-04 19:03:43 +01:00
acidburns	c62f07bf44	Document multi-meter UART mapping and energy-only sender behavior	2026-02-04 15:22:30 +01:00
acidburns	938f490a32	Add multi-meter energy sender schema with UART0/1/2 mode split	2026-02-04 15:22:24 +01:00
acidburns	290ca55b8b	Reset RX signal state at start of each receive window	2026-02-04 15:11:07 +01:00
acidburns	f177e5562d	Drain oversized LoRa packets to prevent RX FIFO corruption	2026-02-04 15:10:37 +01:00
acidburns	cb6929bdc1	Add detailed sender ACK RX diagnostics with reject context	2026-02-04 14:42:44 +01:00
acidburns	c3e5ba3a53	Use protocol constants for ACK airtime window sizing	2026-02-04 14:40:34 +01:00
acidburns	373667ab8a	Document minimal batch/ack protocol and timestamp safety rules	2026-02-04 11:57:59 +01:00
acidburns	f0503af8c7	Refactor LoRa protocol to batch+ack with ACK-based time bootstrap	2026-02-04 11:57:49 +01:00
acidburns	f08d9a34d3	Normalize power/energy output formatting	2026-02-04 02:33:43 +01:00
acidburns	7e5e23e56c	Scale ACK RX window to LoRa airtime - Compute ACK receive window from airtime with bounds and margin - Retry once if initial window misses - Document ACK window sizing	2026-02-04 01:21:42 +01:00
acidburns	1024aa3dd0	Add RX reject reasons to telemetry and UI BACKWARD-INCOMPATIBLE: MeterBatch schema bumped to v2 with err_rx_reject. - Track and log RX reject reasons (CRC/protocol/role/payload/length/id/batch) - Include rx_reject in sender telemetry JSON and receiver web UI - Add lora_receive reject reason logging under SERIAL_DEBUG_MODE	2026-02-04 01:01:49 +01:00
acidburns	0e7214d606	Repeat batch ACKs to cover RX latency - Add ACK_REPEAT_COUNT/ACK_REPEAT_DELAY_MS and repeat ACK sends - Update README with repeat-ACK behavior	2026-02-04 00:53:06 +01:00
acidburns	5a86d1bd30	Add LoRa TX timing diagnostics - Log idle/begin/write/end timing for LoRa TX under SERIAL_DEBUG_MODE - Document TX timing logs in README	2026-02-04 00:48:20 +01:00
acidburns	0a99bf3268	Send batch ACKs immediately after reassembly - Move ACK ahead of MQTT/web work to meet sender 400ms window - Update ACK log format and document early-ACK behavior	2026-02-04 00:36:40 +01:00
acidburns	4e06f7a96d	Log ACK transmit and reject cases - Add debug log for ACK TX with batch/sender/receiver ids - Log rejected ACKs to help diagnose mismatched ids or batches	2026-02-04 00:35:01 +01:00
acidburns	fde4719a50	Improve timesync acquisition and logging - Add boot acquisition mode with wider RX windows until first TimeSync - Log sender TimeSync RX results and receiver TX events - Document acquisition behavior	2026-02-04 00:33:05 +01:00
acidburns	e0d35d49bc	Validate RTC epoch before setting time - Reject out-of-range DS3231 epochs and log accept/reject under SERIAL_DEBUG_MODE - Document RTC validation so LoRa TimeSync can recover	2026-02-04 00:31:10 +01:00
acidburns	e8fb8680cb	Gate slow timesync on LoRa reception - Keep sender in fast TimeSync listen mode until it receives a LoRa beacon - Reset scheduler when interval changes to avoid stuck timing	2026-02-04 00:03:38 +01:00
acidburns	cbf0f7d9b9	Expose timesync error in MQTT and web UI BACKWARD-INCOMPATIBLE: MQTT faults payload now always includes err_last/err_last_text and err_last_age (schema change).	2026-02-04 00:01:38 +01:00
acidburns	f7a2503d7a	Add timesync burst handling and sender-only timeout - Add TimeSync fault code and labels in UI/SD/web docs - Trigger receiver beacon bursts on sender drift, but keep errors sender-local - Sender flags TimeSync only after TIME_SYNC_ERROR_TIMEOUT_MS	2026-02-03 23:40:11 +01:00
acidburns	43893c24d1	Keep receiver timesync fast and extend sender fast window - Receiver now sends time sync every 60s indefinitely (mains powered) - Sender stays in fast timesync listen mode for first 60s even with RTC	2026-02-03 22:28:36 +01:00
acidburns	cd4c99f125	Calibrate battery ADC and document LiPo curve - Add BATTERY_CAL config and debug logging for raw ADC samples - Use LiPo voltage curve (4.2V full, 2.9V empty) for % mapping - Document battery calibration, curve, and debug output in README	2026-02-03 22:12:48 +01:00
acidburns	b8a4c27daa	Average battery ADC samples - Read battery 5 times and average for a steadier voltage estimate	2026-02-02 23:28:54 +01:00
acidburns	2199627a35	Fix OLED autosleep timing and battery sampling cadence - Track last OLED activity to avoid double timeout; keep power gating on transitions - Copy TZ before setenv() in timegm_fallback to avoid invalid pointer reuse - Add BATTERY_SAMPLE_INTERVAL_MS and only refresh cache at batch start when due - Keep battery sampling to a single ADC read (Arduino core lacks explicit ADC power gating)	2026-02-02 23:01:55 +01:00
acidburns	90d830da6f	Keep receiver LoRa in continuous RX - Add lora_receive_continuous() helper and use it after init and TX (ACK/time sync) - Ensure receiver returns to RX immediately after lora_send - Document continuous RX behavior in README	2026-02-02 22:17:09 +01:00
acidburns	237e392c02	Make IEC 62056-21 meter input non-blocking - Add RX state machine with frame buffer, timeouts, and debug counters - Expose meter_poll_frame/meter_parse_frame and reuse existing OBIS parsing - Use cached last-valid frame at 1 Hz sampling to avoid blocking - Document non-blocking meter handling in README	2026-02-02 22:03:58 +01:00
acidburns	8e6c64a18e	Reduce sender power draw (RX windows + CPU/WiFi/ADC/pins) - Add LoRa idle/sleep/receive-window helpers and use short RX windows for ACK/time sync - Schedule sender time-sync windows (fast/slow) and track RX vs sleep time in debug - Lower sender power (80 MHz CPU, WiFi/BT off, reduced ADC sampling, unused pins pulldown) - Make SERIAL_DEBUG_MODE a build flag, add prod envs with debug off, and document changes	2026-02-02 21:44:04 +01:00
acidburns	a4d9be1903	Harden history device ID validation and SD download filename	2026-02-02 21:19:44 +01:00
acidburns	0e12b406de	Harden web UI auth, input handling, and SD path validation - Add optional Basic Auth with NVS-backed credentials and STA/AP flags; protect status, wifi, history, and download routes - Stop pre-filling WiFi/MQTT/Web UI password fields; keep stored secrets on blank and add clear-password checkboxes - Add HTML escaping + URL encoding helpers and apply to user-controlled strings; add unit test - Harden /sd/download path validation (prefix, length, dotdot, slashes) and log rejections - Enforce protocol version in LoRa receive and release GPIO14 before SD init - Update README security, SD, and GPIO sharing notes	2026-02-02 21:08:05 +01:00
acidburns	b5477262ea	Add SD history UI and pin remap - Add SD history chart + download listing to web UI - Use HSPI for SD and fix SD pin mapping - Swap role/OLED control pins and update role detection - Update README pin mapping and SD/history docs	2026-02-02 01:43:54 +01:00
acidburns	d32ae30014	Move AP credentials to config and clarify STA UI access	2026-02-02 00:23:52 +01:00
acidburns	f3af5b3f1c	Add SD logging and update docs - Add optional microSD CSV logging per sender/day on receiver - Wire logger into receiver packet handling - Document new batch header fields, build envs, and SD logging - Make sender links open in a new tab	2026-02-02 00:22:35 +01:00
acidburns	5085b9ad3d	Improve receiver web UI fields and manual	2026-02-02 00:00:55 +01:00
acidburns	a03c2cdb07	Include sender error counters in batch payload	2026-02-02 00:00:29 +01:00
acidburns	13f2f02e42	Tidy sender page layout and use SF12	2026-02-01 23:38:43 +01:00
acidburns	16c1b90b1e	Add payload codec test envs and enable serial debug	2026-02-01 22:54:07 +01:00
acidburns	e5c4e04ff9	Update README for binary batch payload and SF11	2026-02-01 22:42:26 +01:00
acidburns	e24798eb55	Use compact binary payload for LoRa batches	2026-02-01 22:37:21 +01:00
acidburns	d27b68c1cc	adjust batch ack timing and rename e_wh field	2026-02-01 21:53:18 +01:00
acidburns	01f4494f00	expand web ui with batch table and manual	2026-02-01 21:04:34 +01:00
acidburns	50436cd0bb	document batching updates and restore bat_v in batches	2026-02-01 20:59:45 +01:00
acidburns	a0080b249d	increase lora throughput and improve receiver display	2026-02-01 20:09:44 +01:00
acidburns	876c572bb3	force watchdog reinit for custom timeout	2026-02-01 19:37:47 +01:00
acidburns	13b4025443	add lora send bypass for debugging	2026-02-01 19:34:28 +01:00
acidburns	7f31b9dd95	instrument tx timings for watchdog analysis	2026-02-01 19:21:59 +01:00
acidburns	660d1cde94	prevent watchdog from killing while printing json	2026-02-01 18:59:12 +01:00
acidburns	f9bcfbd5f2	serial debugging console implemented, enable via config.h	2026-02-01 18:43:06 +01:00
acidburns	fbd18b2e78	no sleep while ack pending	2026-02-01 18:27:58 +01:00
acidburns	b4344db828	attempted lora fix: timeout increase	2026-02-01 17:53:01 +01:00
acidburns	22ed41b55c	Add sender queue display and batch timing	2026-02-01 17:46:26 +01:00
acidburns	430b0d7054	Update ESP32 platform and LoRa batching	2026-02-01 17:03:08 +01:00
acidburns	16c65744e3	Keep in-flight batch until ACK	2026-01-31 02:09:34 +01:00
acidburns	8fba67fcf3	Update batch schema and add ACK handling	2026-01-31 01:53:02 +01:00