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MeshCoreNG Protocol Audit

Sources inspected:

  • Local Python package: /home/michel/source/PyMesh/venv/lib/python3.12/site-packages/meshcore
  • Local firmware/docs: /home/michel/source/MeshCoreNG
  • Upstream CLI: https://github.com/meshcore-dev/meshcore-cli

Transport

BLE uses Nordic UART Service:

  • service 6E400001-B5A3-F393-E0A9-E50E24DCCA9E
  • write/RX 6E400002-B5A3-F393-E0A9-E50E24DCCA9E
  • notify/TX 6E400003-B5A3-F393-E0A9-E50E24DCCA9E

BLE payloads are raw MeshCore companion command/response frames.

USB serial wraps outbound companion payloads as:

  • start byte 0x3c
  • payload length uint16 little-endian
  • payload bytes

Serial inbound frames use:

  • start byte 0x3e
  • payload length uint16 little-endian
  • payload bytes

Python rejects serial payload lengths over 300 bytes and resynchronizes by searching for the next inbound start byte.

Command Surface

The Android app currently implements the Phase 1 core commands:

  • info: command 0x01 0x03 " mccli", waits for SELF_INFO or ERROR
  • firmware version: command 0x16 0x03, waits for DEVICE_INFO or ERROR
  • nodes: command 0x04 [lastmod:u32le], consumes contact frames until CONTACT_END
  • statistics: command 0x38 <statsType>, waits for STATS
  • reboot: command 0x13 "reboot", waits for OK or ERROR

The enum tables in lib/core/packets/mesh_enums.dart mirror the Python meshcore.packets values.

Monitor Frames

RF log push frames use packet type 0x88. Payload layout:

  • signed SNR byte scaled by 4
  • signed RSSI byte
  • raw MeshCore RF packet payload

The RF packet header uses:

  • route type: header & 0x03
  • payload type: (header & 0x3c) >> 2
  • payload version: (header & 0xc0) >> 6
  • transport code is present for route types 0x00 and 0x03
  • path byte high two bits encode hash size minus one
  • path byte low six bits encode hop/hash count

The monitor parser handles malformed frames with sentinel values instead of throwing.

Compatibility Notes

meshcore-cli is a higher-level interactive client. Its README confirms BLE, Serial, and TCP companion transports, command chaining, node/contact management, repeater command forwarding, channel echoes, and log-based path/RSSI/SNR inspection. Protocol truth is in the meshcore Python package used by that CLI.