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