fix(nebula_hesai): ignore fault message packets in the decoder - #521

PR Type

• Bug Fix

Related Links

• Split from feat: support AT128P and FTX140 #520 as requested in feat: support AT128P and FTX140 #520 (comment)
• TIER IV INTERNAL LINK

Description

Some Hesai sensors (e.g. the AT128P) send fault messages to the data port alongside point cloud packets. These packets start with SOP 0xCDDC and are 99 bytes long.

• Before: HesaiDecoder treated them as truncated point cloud packets. It logged Packet size mismatch: 99 | Expected at least: ... for each one, which is about 200 errors per second per sensor and buries the real errors in the log.
• After: HesaiDecoder::unpack() checks the SOP first and returns the new DecodeError::PACKET_IGNORED for fault messages, without logging. All other packets are handled as before, so truncated point cloud packets are still reported as PACKET_PARSE_FAILED.

DecodeError::PACKET_IGNORED is meant for any valid packet that carries no point cloud data (e.g. IMU or fault message packets), so other decoders can use it too.

The content of the fault messages is not decoded.

Review Procedure

1. Build and run the unit tests:

   colcon build --packages-up-to nebula_hesai --cmake-args -DBUILD_TESTING=ON
   colcon test --packages-select nebula_hesai nebula_hesai_decoders nebula_hesai_hw_interfaces
   colcon test-result --verbose

   New test: test_hesai_fault_message feeds a HesaiDecoder<PandarAT128> two packets:

   • A fault message. It must return PACKET_IGNORED and log no error.
   • A truncated point cloud packet. It must still return PACKET_PARSE_FAILED and log one error.

Test results

• Unit tests: 158 tests in nebula_hesai, nebula_hesai_decoders and nebula_hesai_hw_interfaces pass (ROS 2 Jazzy, Agnocast disabled).
• pre-commit: passes on all changed files.

Remarks

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