# DD3-LoRa-Bridge-MultiSender

Firmware for LilyGO T3 v1.6.1 (`ESP32 + SX1276 + SSD1306`) that runs as either:
- `Sender` (PIN `GPIO14` HIGH): reads one IEC 62056-21 meter, batches samples, sends over LoRa.
- `Receiver` (PIN `GPIO14` LOW): receives/ACKs batches, publishes MQTT, serves web UI, logs to SD.

## Current Architecture

- 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`).
- Sender batches up to `30` samples and retries on missing ACK (`BATCH_MAX_RETRIES=2`, retry policy `Keep`).
- Receiver uses STA mode when config is valid, otherwise AP fallback with web config.

## LoRa Frame Protocol (Current)

On-air frame format:

`[msg_kind:1][device_short_id:2][payload...][crc16:2]`

`msg_kind`:
- `0` = `BatchUp`
- `1` = `AckDown`

### `BatchUp`

Transport is chunked (`batch_id`, `chunk_index`, `chunk_count`, `total_len`) and reassembled before payload decode.

Payload codec (`src/payload_codec.cpp`) currently uses:
- `kMagic=0xDDB3`
- `kSchema=2`
- metadata: sender, batch, timestamp, interval, battery, fault counters
- data arrays: `energy_wh[]`, `p1_w[]`, `p2_w[]`, `p3_w[]`

`n == 0` is valid and used for sync request packets.

### `AckDown` (7 bytes)

`[flags:1][batch_id_be:2][epoch_utc_be:4]`

- `flags bit0`: `time_valid`
- Receiver repeats ACK (`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`).

## Time Bootstrap Guardrail

On sender boot:
- `g_time_acquired=false`
- no normal sampling/transmit yet
- sync request every `SYNC_REQUEST_INTERVAL_MS` (15s)

Only after valid ACK time is received:
- system time is set
- normal 1 Hz sampling and periodic LoRa batch transmit start

This blocks pre-threshold timestamps from MQTT/SD paths.

## Sender Meter Path

Implemented in `src/meter_driver.cpp` + sender loop in `src/main.cpp`:

- UART: `Serial2`, RX pin `GPIO34` (`PIN_METER_RX`), `9600 7E1`
- Frame detection: starts at `'/'`, ends at `'!'`, timeout protection included
- Parsed OBIS values:
  - `1-0:1.8.0` (total energy)
  - `1-0:16.7.0` (total power)
  - `1-0:36.7.0`, `56.7.0`, `76.7.0` (phase powers)
- `1-0:1.8.0*Wh` is automatically scaled to kWh

Sender samples every second and transmits batches every 30 seconds.

## Receiver Behavior

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 samples, log to SD, update web UI, publish MQTT.

## MQTT Topics and Payloads

State topic:
- `smartmeter/<device_id>/state`

Fault topic (retained):
- `smartmeter/<device_id>/faults`

State JSON fields (`src/json_codec.cpp`):
- `id`, `ts`, `e_kwh`
- `p_w`, `p1_w`, `p2_w`, `p3_w`
- `bat_v`, `bat_pct`
- optional link fields: `rssi`, `snr`
- fault/reject fields: `err_last`, `rx_reject`, `rx_reject_text` (+ non-zero counters)

Home Assistant discovery is enabled (`ENABLE_HA_DISCOVERY=true`) and publishes config topics under:
- `homeassistant/sensor/<device_id>/<key>/config`

## Web UI, Wi-Fi, Storage

- Wi-Fi/MQTT/NTP/web-auth config persists in Preferences (`wifi_manager`).
- AP fallback SSID prefix: `DD3-Bridge-`.
- Default web credentials: `admin/admin`.
- SD logging enabled (`ENABLE_SD_LOGGING=true`).

## Build Environments

From `platformio.ini`:

- `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`

Example:

```bash
~/.platformio/penv/bin/pio run -e lilygo-t3-v1-6-1
```

## Test Mode

`ENABLE_TEST_MODE` replaces normal sender/receiver loops with dedicated test loops (`src/test_mode.cpp`).
It sends/receives JSON test frames and publishes to `smartmeter/<device_id>/test`.
