[crsf] Add support for link statistics message #25693

niklaut · 2025-10-01T09:39:35Z

Solved Problem

Add support for ELRS and CRSF link statistics messages.
Allow setting CRSF baudrate via parameters, some receivers use slightly different baudrates than 420000
Extend the packet reception timeout to 0.5s.
Add ability to inject messages into the buffer (disabled by default via KConfig option)
Version the input_rc message and add it to the DDS bridge.

Changelog Entry

For release notes:

Feature: Add CRSF and ELRS link statistics messages

Alternatives

We could also split the input_rc message into just the control values and then a input_rc_link message with all the link quality metrics. But that involves probably quite a lot of refactoring.

Test coverage

Tested in hardware with CRSF and ELRS receivers

github-actions · 2025-10-01T09:45:29Z

🔎 FLASH Analysis

px4_fmu-v5x [Total VM Diff: 920 byte (0.05 %)]

    FILE SIZE        VM SIZE    
--------------  -------------- 
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  [NEW]     +42  [ = ]       0    ProcessElrsStatus()
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px4_fmu-v6x [Total VM Diff: 920 byte (0.05 %)]

    FILE SIZE        VM SIZE    
--------------  -------------- 
+0.0%    +920  +0.0%    +920    .text
  [NEW]    +352  [NEW]    +352    ucdr_serialize_input_rc()
   +12%    +156   +12%    +156    CrsfRc::Run()
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  +5.9%      +1  [ = ]       0    CrsfRc::CrsfRc()
  [NEW]     +42  [ = ]       0    ProcessElrsStatus()
  [NEW]     +48  [ = ]       0    ProcessLinkStatisticsTx()
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  [NEW]     +48  [ = ]       0    _GLOBAL__sub_I__ZN6CrsfRcC2EPKcm
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  [NEW]     +32  [ = ]       0    CSWTCH.188
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  [NEW]     +32  [ = ]       0    ProcessElrsStatus()
  [NEW]     +32  [ = ]       0    ProcessLinkStatisticsTx()
  [DEL]     -64  [ = ]       0    _GLOBAL__sub_I__ZN6CrsfRcC2EPKc
  [NEW]     +64  [ = ]       0    _GLOBAL__sub_I__ZN6CrsfRcC2EPKcm
  [NEW]     +32  [ = ]       0    ucdr_serialize_input_rc()
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+0.0% +8.41Ki  +0.0%    +920    TOTAL

Updated: 2025-10-08T05:20:21

src/drivers/rc/crsf_rc/CrsfParser.cpp

dagar · 2025-10-01T19:54:45Z

Version the input_rc message and add it to the DDS bridge.

Do people really need both uncalibrated (input_rc) and calibrated (manual_control_setpoint, etc) data exposed? I'd send everything if we could afford it...

I'd also try to avoid making msgs versioned by default and only do it once strictly needed. We don't want to force unnecessary data migration work on people if it doesn't actually matter.

PetervdPerk-NXP · 2025-10-01T21:23:05Z

Version the input_rc message and add it to the DDS bridge.

Do people really need both uncalibrated (input_rc) and calibrated (manual_control_setpoint, etc) data exposed? I'd send everything if we could afford it...

I'd also try to avoid making msgs versioned by default and only do it once strictly needed. We don't want to force unnecessary data migration work on people if it doesn't actually matter.

I want to drop a bit of a bomb here: I think message versioning inside the PX4 firmware was a bad idea from the start. The MCU is the wrong place to be solving this. Adding versioning at the firmware level complicates things unnecessarily and forces migrations that don’t actually bring value for most users.

If we really want some safety guard, a lightweight hash/checksum is enough. With that in place, a ROS 2 node can take care of everything else if needed including handling conversions or bridging between formats just using optional hashes for integrators that suffer from this problem. This keeps PX4 clean and avoids burdening the firmware with problems that belong on the integration side.

hamishwillee

@niklaut Can you also update https://docs.px4.io/main/en/telemetry/crsf_telemetry.html#telemetry-messages - and add a note in https://docs.px4.io/main/en/releases/main.html

niklaut · 2025-10-02T11:14:21Z

Can you also update https://docs.px4.io/main/en/telemetry/crsf_telemetry.html#telemetry-messages

I think those are different messages relating to something with OpenTX. The table is copied from the PDF, I don't think I should add anything to it.

hamishwillee · 2025-10-02T22:57:48Z

Can you also update https://docs.px4.io/main/en/telemetry/crsf_telemetry.html#telemetry-messages

I think those are different messages relating to something with OpenTX. The table is copied from the PDF, I don't think I should add anything to it.

Fair enough. I guess my point is "if this is a message that users can get and might find useful, we should document it". If not, ignore.

docs/en/releases/main.md

github-actions · 2025-10-08T05:15:13Z

No flaws found

niklaut force-pushed the pr-crsf-status-messages branch from a7e0589 to 66ed0e3 Compare October 1, 2025 09:46

niklaut mentioned this pull request Oct 1, 2025

[vtx] Add support for VTX control via Tramp and SmartAudio protocols #25694

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11 tasks

dakejahl previously approved these changes Oct 1, 2025

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dagar reviewed Oct 1, 2025

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hamishwillee reviewed Oct 1, 2025

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niklaut dismissed dakejahl’s stale review via f5a0664 October 2, 2025 11:11

niklaut force-pushed the pr-crsf-status-messages branch from 66ed0e3 to f5a0664 Compare October 2, 2025 11:11

github-actions bot added the Documentation 📑 label Oct 2, 2025

niklaut added 5 commits October 3, 2025 12:31

[crsf_rc] Add support for link statistic messages

28194f5

[crsf_rc] Allow setting the baudrate via parameter

91a79da

[crsf_rc] Extend the RC packet reception timeouts to 0.5s

5c32c42

[crsf_rc] Add ability to inject buffers for development

4fb4f00

[dds] Version input_rc and output it on DDS

97de489

niklaut force-pushed the pr-crsf-status-messages branch from f5a0664 to 97de489 Compare October 3, 2025 10:32

hamishwillee reviewed Oct 8, 2025

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[crsf] Add support for link statistics message #25693

[crsf] Add support for link statistics message #25693

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niklaut commented Oct 1, 2025

Solved Problem

Changelog Entry

Alternatives

Test coverage

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