# Meshtastic backend

[Meshtastic](https://meshtastic.org) protocol backend for the mesh service (`mesh-module`). It registers itself with
`mesh_backend_register()` as `meshtastic`. It has a GPL-3.0 license, and none of its headers are part of the app SDK.

Supported:

- The LongFast preset (SF11, 250 kHz, CR 4/5, sync word 0x2B), in the frequency slot that the primary channel's
  name selects within the region's band, like Meshtastic does.
- Channels: the primary channel is preconfigured as "LongFast" with the default key. More channels can be added with
  `mesh_set_channel()`, with a 1-byte PSK index, or a 16 or 32-byte key.
- Text messages on channels, and direct messages to and from nodes. Direct messages request an acknowledgement and
  received ones are acknowledged.
- NodeInfo: sent at start and every 3 hours, received NodeInfo provides node names.

The node number is random and stored in the backend's data directory. The node doesn't rebroadcast packets for
others (like the CLIENT_MUTE role).

Not implemented: public key (PKI) encryption of direct messages, other modem presets, positions and telemetry.
Direct messages are encrypted with the primary channel's key, which current firmware still accepts.