# DD3-LoRa-Bridge-MultiSender

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.

## 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`), 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.

## LoRa Frame Protocol (Current)

Frame format on-air:

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

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

### `BatchUp`

`BatchUp` is chunked in transport (`batch_id`, `chunk_index`, `chunk_count`, `total_len`) and then decoded via `payload_codec`.

Payload header contains:
- fixed magic/schema fields (`kMagic=0xDDB3`, `kSchema=2`)
- `schema_id`
- sender/batch/time/error metadata

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

`n == 0` is used as sync request (no meter samples).

### `AckDown` (7 bytes)

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

- `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`).

## Time Bootstrap Guardrail

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

This prevents publishing/storing pre-threshold timestamps.

## Multi-Meter Sender Behavior

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

- 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`)

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`

Default RX pins:
- Meter1: `GPIO34` (`Serial2`)
- Meter2: `GPIO25` (`Serial1`)
- Meter3: `GPIO3` (`Serial`, prod only because debug serial is disabled)

## 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 to `MeterData`, 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`

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)

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`.

## 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

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 plain JSON test frames and publishes to `smartmeter/<device_id>/test`.