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https://github.com/f4exb/sdrangel.git
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Tom Hensel
dd0b2a4f1d
Both plugin readmes listed the SWGMeshtastic* placeholder as an outstanding item needing dedicated SWGMeshcore* schemas. This PR provides exactly that — strike the stale todo and note the resolution.
78 lines
3.3 KiB
Markdown
78 lines
3.3 KiB
Markdown
<h1>MeshCore modulator plugin</h1>
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<h2>Introduction</h2>
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This plugin codes and modulates a transmission signal based the LoRa Chirp
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Spread Spectrum (CSS) modulation scheme with a MeshCore payload.
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MeshCore (https://github.com/meshcore-dev/MeshCore, MIT) is a mesh networking
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protocol distinct from Meshtastic. The two share LoRa as the PHY layer but
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differ at the packet layer (envelope, addressing, crypto, routing). This
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plugin builds and transmits MeshCore wire packets — ADVERT, TXT_MSG,
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ANON_REQ, GRP_TXT, ACK — using vendored crypto (Monocypher for Ed25519 +
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X25519, tiny-AES-c for AES-128-ECB, Qt SHA-256 + hand-rolled HMAC-SHA256).
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The encode pipeline is derived from the Meshtastic modulator
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(LoRa-SDR-based, configurable BW/SF/CR/sync). MeshCore EU defaults
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are baked in: **869.618 MHz / 62.5 kHz / SF 8 / CR 4/8**, sync word
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0x12.
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This is a companion to the MeshCore demodulator plugin
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(`channelrx/demodmeshcore`) and the standalone `lora_trx` headless
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transceiver in gr4-lora.
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<h2>Status</h2>
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Functional surfaces:
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- TX of ADVERT / TXT_MSG / ANON_REQ / GRP_TXT / ACK / PATH / CTRL
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via the `MESHCORE:` command syntax below.
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- LoRa PHY with MeshCore EU radio defaults.
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- Identity store: an Ed25519 seed is persisted under the application
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support directory, auto-loaded by `MeshcoreMod`, and used to sign
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outgoing ADVERTs. Encoder output is bit-exact against gr4-lora's
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`meshcore_tx.py::build_advert_raw` reference for the same seed and
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timestamp.
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- REST sendNow action (`SWGMeshcoreModActions`) for programmatic
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single-packet TX.
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- Radio parameters (BW, SF, CR, preamble length, frequency offset)
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exposed via combo controls. BW combo includes 62500 / 125000 /
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250000 Hz — the bandwidths used by the MeshCore firmware CLI's
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`set radio freq_MHz,bw_kHz,sf,cr` command.
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- Preset combo populated with the well-known MeshCore regional
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defaults (EU_NARROW, EU_LONG_RANGE, EU_MEDIUM_RANGE, AU,
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AU_VICTORIA, CZ_NARROW, EU_433_LONG_RANGE, NZ, NZ_NARROW, PT_433,
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PT_868, CH, USA, VN, USER). Default is `EU_NARROW` (869.618 MHz /
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SF 8 / BW 62.5 kHz / CR 4/8). Selecting a preset applies its
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freq/BW/SF/CR via `modemmeshcore::command::applyMeshcorePreset`.
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- The Region and Channel controls are hidden: region is implicit
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in the preset frequency, and MeshCore has no numbered Channel
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concept.
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Outstanding:
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- WebAPI schema now uses dedicated `SWGMeshcoreModSettings` /
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`SWGMeshcoreModReport` / `SWGMeshcoreModActions` schemas (no longer
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a placeholder).
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<h2>MESHCORE: command syntax</h2>
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Send a MeshCore wire packet by setting the channel's "Text message" to a
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line starting with `MESHCORE:`:
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```
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MESHCORE: type=advert; seed=<hex64>; name=NodeA
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MESHCORE: type=txt_msg; seed=<hex64>; dest=<hex64>; text=Hello
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MESHCORE: type=anon_req; seed=<hex64>; dest=<hex64>; data=<hex>
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MESHCORE: type=grp_txt; channel=public; text=Hello group
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MESHCORE: type=ack; dest=<hex64>; msg_hash=<hex8>
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```
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Optional radio overrides on any line: `sf=8`, `bw=62500`, `cr=8` (for 4/8),
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`sync=0x12`, `freq=869.618M`, `preamble=8`.
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<h2>References</h2>
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- MeshCore protocol: https://github.com/meshcore-dev/MeshCore
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- gr4-lora python implementation: scripts/src/lora/core/meshcore_crypto.py
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- Vendored Monocypher: https://monocypher.org (BSD-2-Clause OR CC0-1.0)
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- Vendored tiny-AES-c: https://github.com/kokke/tiny-AES-c (public domain)
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