sdrangel/plugins/channelrx/demodmeshcore

MeshCore demodulator plugin

Introduction

This plugin demodulates and decodes incoming MeshCore wire packets. It is the RX counterpart of the MeshCore modulator plugin (channeltx/modmeshcore) and the standalone lora_trx headless transceiver in gr4-lora.

The decode pipeline is derived from the Meshtastic demodulator (LoRa-SDR-based, configurable BW/SF/CR/sync). MeshCore EU defaults are baked in: 869.618 MHz / 62.5 kHz / SF 8 / CR 4/8, sync word 0x12.

Status

Functional surfaces:

• LoRa PHY decode covering MeshCore EU radio params (preamble, sync, CFO, soft demod), with the following adjustments: m_nbSymbolsMax default raised to 1023 (256 symbols are needed for a 120-byte ADVERT at SF=8 / CR=4/8; the prior default of 255 clipped this); channel filter cutoff widened to BW/1.25; interpolator upsample regime in feed(); m_chirp initialization aligned to the standard LoRa upchirp.
• Packet::decodeFrame (in modemmeshcore) for ADVERT / TXT_MSG / GRP_TXT / ANON_REQ / ACK / PATH / CTRL packets.
• ADVERT signature verification (Ed25519 via vendored Monocypher).
• Auto-augmented PSK for public channels.
• Optional UDP JSON sink (sendJsonViaUDP) for off-process observation.
• Radio parameters (BW, SF, CR, preamble length, frequency offset) exposed via combo controls. BW combo includes 62500 / 125000 / 250000 Hz — the bandwidths used by the MeshCore firmware CLI's set radio freq_MHz,bw_kHz,sf,cr command.
• Preset combo populated with the well-known MeshCore regional defaults (EU_NARROW, EU_LONG_RANGE, EU_MEDIUM_RANGE, AU, AU_VICTORIA, CZ_NARROW, EU_433_LONG_RANGE, NZ, NZ_NARROW, PT_433, PT_868, CH, USA, VN, USER). Default is EU_NARROW (869.618 MHz / SF 8 / BW 62.5 kHz / CR 4/8). Selecting a preset applies its freq/BW/SF/CR via modemmeshcore::command::applyMeshcorePreset.
• The Region and Channel controls are hidden: region is implicit in the preset frequency, and group channels are managed via the keys dialog rather than a numbered Channel selector.

Outstanding:

• WebAPI schema now uses dedicated SWGMeshcoreDemodSettings / SWGMeshcoreDemodReport schemas (no longer a placeholder).

References

• MeshCore protocol: https://github.com/meshcore-dev/MeshCore
• gr4-lora python decoder: scripts/src/lora/decoders/meshcore.py
• gr4-lora python crypto: scripts/src/lora/core/meshcore_crypto.py
• Vendored Monocypher: https://monocypher.org (BSD-2-Clause OR CC0-1.0)
• Vendored tiny-AES-c: https://github.com/kokke/tiny-AES-c (public domain)