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feat: adopt ELRS USB CRSF frame format, add skeleton modules

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Switch CRC from CCITT (0x07) to DVB-S2 (0xD5) to match ELRS.
Adopt ELRS USB frame format: [addr][length][type][payload][crc].
Update frame type constants to match current ELRS protocol values.

New skeleton modules (stub implementations with TODO comments):
  - crsf_telemetry.h/.c: telemetry decoders (GPS, battery, link..)
  - crsf_stream.h/.c: incremental streaming frame reader
  - crsf_param.h/.c: parameter protocol (read/write/set_power)

Retained old frame format as *_legacy functions for backward
compatibility with existing telemetry tool and tests.

Add cel_serial_find_elrs_port() and cel_serial_open_probe()
stubs to serial module for port auto-detection and baud probing.
This commit is contained in:
portersky
2026-06-14 20:47:56 +02:00
parent c42ec407da
commit df3d399610
16 changed files with 919 additions and 156 deletions
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AGENTS.md
+18 -16
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@@ -131,19 +131,22 @@ Added unit tests for empty, single-byte, and known-value cases.
```text
celrs/
crsf.h / crsf.c CRSF protocol: CRC8, frame parse/build
serial.h / serial.c Serial port abstraction (Win/POSIX stubs)
logger.h / logger.c Level-filtering logger
log_write.h/.c stdout log sink
crsf.h / crsf.c CRSF protocol: CRC8/DVB-S2, frame build/parse
crsf_telemetry.h/.c Telemetry frame decoders (GPS, battery, link..)
crsf_stream.h/.c Incremental streaming frame reader
crsf_param.h/.c Parameter protocol (read/write/set_power)
serial.h / serial.c Serial port abstraction (Win/POSIX)
logger.h / logger.c Level-filtering logger
log_write.h/.c stdout log sink
tools/
telemetry.c Telemetry read tool
telemetry.c Telemetry read tool
tests/
test_crsf.c CRSF CRC, parse, build tests
test_serial.c Serial open/close/stub tests
test_logger.c Logger level-filtering tests
test_crsf.c CRSF CRC, parse, build tests
test_serial.c Serial open/close/stub tests
test_logger.c Logger level-filtering tests
deps/
FindUnity.cmake Fetches Unity v2.6.1 via ZIP
FindCMock.cmake Fetches CMock v2.6.0 via ZIP
FindUnity.cmake Fetches Unity v2.6.1 via ZIP
FindCMock.cmake Fetches CMock v2.6.0 via ZIP
```
## TDD Workflow
@@ -239,9 +242,8 @@ The project supports Windows, Linux, macOS, Emscripten, and Android via
CRSF is the Crossfire Serial Protocol used by ELRS. Key points:
- Frame header is always `0xC8`
- CRC8-CCITT with polynomial `0x07`, init `0x00`
- CRC is computed over: destination + source + type + size + payload
- Standard baud rate for ELRS CRSF is 400000 bps
- TX modules expose CRSF over USB serial (appears as COM port on Windows,
/dev/ttyUSB* on Linux)
- Frame format: [addr][length][type][payload...][crc]
- CRC8/DVB-S2 with polynomial `0xD5`, init `0x00`
- CRC is computed over: type + payload
- Address byte varies: `0xC8` (host), `0xEE` (module), `0xEF` (lua)
- Standard baud rate for ELRS CRSF is 400000 bps (probe 921600 first)