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97 lines
3.2 KiB
Markdown
97 lines
3.2 KiB
Markdown
# MeshCore Protocol Specification
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## Section 18: Companion Protocol
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### Overview
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The companion protocol enables BLE (Bluetooth Low Energy) and serial
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communication between a MeshCore radio and a companion app (phone, tablet, or
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computer). It uses a binary framing format over the Nordic UART Service (NUS)
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BLE profile.
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### BLE Service
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| UUID | Description |
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|------|-------------|
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| `6E400001-B5A3-F393-E0A9-E50E24DCCA9E` | Nordic UART Service |
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| `6E400002-...` | RX Characteristic (app writes to radio) |
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| `6E400003-...` | TX Characteristic (radio notifies app) |
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### Frame Format
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Each companion protocol frame consists of a 1-byte type identifier followed by
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variable-length data:
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```
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[type(1)][data(0-171)]
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```
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Maximum frame size is 172 bytes.
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### Message Types (Radio to App)
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| Type | Value | Description |
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|------|-------|-------------|
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| PACKET_CHANNEL_MSG_RECV | 0x01 | Channel message received |
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| PACKET_CONTACT_MSG_RECV | 0x02 | Contact message received |
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| PACKET_ADV_RECV | 0x03 | Advertisement received |
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| PACKET_CONTACT_MSG_RECV_V3 | 0x04 | Contact message V3 (includes SNR) |
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| PACKET_CHANNEL_MSG_RECV_V3 | 0x05 | Channel message V3 (includes SNR) |
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### Command Types (App to Radio)
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| Command | Value | Description |
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|---------|-------|-------------|
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| CMD_APP_START | 0x01 | Initialize connection |
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| CMD_DEVICE_QUERY | 0x02 | Query device info |
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| CMD_SET_CHANNEL | 0x03 | Set active channel |
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| CMD_SEND_CHANNEL_MESSAGE | 0x04 | Send message to channel |
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| CMD_SEND_CONTACT_MESSAGE | 0x05 | Send message to contact |
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| CMD_GET_CONTACTS | 0x06 | Get contact list |
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| CMD_GET_CHANNELS | 0x07 | Get channel list |
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| CMD_SET_TIME | 0x08 | Set device time |
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| CMD_ADD_CONTACT | 0x09 | Add a contact |
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| CMD_ADD_CHANNEL | 0x0A | Add a channel |
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| CMD_SEND_LOGIN | 0x0B | Login to room/repeater |
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| CMD_GET_SETTINGS | 0x0C | Get device settings |
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| CMD_SET_SETTINGS | 0x0D | Set device settings |
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| CMD_REMOVE_CONTACT | 0x0E | Remove a contact |
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| CMD_REMOVE_CHANNEL | 0x0F | Remove a channel |
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| CMD_SHARE_CONTACT | 0x10 | Share contact info |
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| CMD_SET_ADV_NAME | 0x11 | Set advertisement name |
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| CMD_REBOOT | 0x12 | Reboot device |
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| CMD_SEND_RAW | 0x13 | Send raw packet |
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### Connection Sequence
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1. Scan for BLE devices advertising the Nordic UART Service.
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2. Connect and discover services.
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3. Enable notifications on the TX characteristic.
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4. Send `CMD_APP_START` to initialize.
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5. Send `CMD_DEVICE_QUERY` to get device info.
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6. Send `CMD_SET_TIME` to synchronize clock.
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7. Send `CMD_GET_CONTACTS` and `CMD_GET_CHANNELS` to fetch state.
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### Byte Order
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All multi-byte integers in the companion protocol are **little-endian**, except
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for CayenneLPP sensor data which uses **big-endian**.
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### Message Length Limit
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Text messages are limited to 133 characters.
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### MTU Considerations
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The default BLE MTU is 23 bytes (20 bytes of payload). For complex operations,
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implementations SHOULD request a larger MTU (up to 512 bytes).
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### Cross-References
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- [Section 1: Wire Format](01-wire-format.md) — Underlying packet format
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- Test vectors: [`corpus/companion/`](https://git.swaits.com/swaits/meshcore-spec/src/branch/main/versions/v0.1.0/corpus/companion/)
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### Reference Implementation
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- `docs/companion_protocol.md` in the MeshCore repository
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