54 lines
2.6 KiB
Markdown
54 lines
2.6 KiB
Markdown
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# OBU transmit firmware - Phase 2 (in progress: HLN-SV DENM beacon)
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Started. See `docs/04-transmit-setup.md` in the project root for build/flash
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steps and how to validate this against your own sniffer.
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## Toolchain: use a dedicated terminal (ESP-IDF 5.5.4)
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This project builds against the **global** ESP-IDF 5.5.4, NOT the 6.1 checkout
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that `obu-firmware` uses. Keep one terminal per toolchain and never export both
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in the same window - the second export inherits the first's
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`IDF_PYTHON_ENV_PATH` and then fails every dependency check (`click`,
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`esptool`, `cryptography`, ... "not met"). That is env-var bleed, not a broken
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install: do **not** run `install.bat` to "fix" it, that damages one of the two
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environments.
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| Terminal | Export | Project |
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|---|---|---|
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| Transmitter | `C:\Espressif\frameworks\esp-idf-v5.5.4\export.ps1` | this one |
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| OBU | `...\micrOBU_workspace\its-g5-receiver-firmware\esp-idf\export.ps1` | `obu-firmware` |
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If a terminal has already been used for the other IDF, clear the state first:
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```powershell
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$env:IDF_PYTHON_ENV_PATH = $null; $env:IDF_PATH = $null
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```
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Also note `build/` here was regenerated from scratch (its CMake cache still
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referenced an older source path under `micrOBU_workspace/v2x-obu-esp32c5/`,
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which makes `idf.py fullclean` refuse to run). If that error reappears, delete
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`build/` manually rather than fighting it.
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## CAM encoding
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`main/cam.c` IS compiled here (unlike `obu-firmware`'s copy, which is a
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reference only). It must stay bit-identical to `obu-firmware/main/cam.c` and
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the app's `CamUperCodec.kt` - all three encode the same wire format, and a
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one-bit divergence in any of them is invisible on the bench but wrong against
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real equipment. See the `CurvatureCalculationMode` comment in that file.
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Implements one profile so far: **HLN-SV** (aftermarket stationary recovery
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vehicle), causeCode 94 (stationaryVehicle), subCauseCode 0, active while the
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hazard-light GPIO is grounded. No location/alacarte containers.
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- `main/main.c` - entry point, the `phy_11p_set`/`phy_change_channel(5900,...)`
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register hack, GPIO polling, TX loop
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- `main/denm.c` / `.h` - ASN.1 UPER encoding of a minimal DENM
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- `main/geonet.c` / `.h` - GeoNetworking Basic/Common/SHB headers + BTP-B
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- `main/dot11p.c` / `.h` - 802.11 OCB (QoS Data, broadcast) frame + LLC/SNAP
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Known gaps, tracked as TODOs in the source: no real GNSS (lat/long hardcoded
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0), no real time source (detectionTime/referenceTime hardcoded 0, decodes as
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2004-01-01), fixed (non-rotating) pseudonym MAC, SHB instead of GeoBroadcast
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(no multi-hop forwarding), unsecured (no IEEE 1609.2 signing).
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