SBUS not detected

Ansel Misfeldt · 19 Dec 2024, 18:15

Hello,

I'm trying to connect an SBUS receiver to a particular Flight Core v2 and it's not detecting it. The same cabling and receiver works just fine on a VOXL Flight, but this particular Flight Core v2 board won't detect it.

We haven't used SBUS with this particular board before (previously was using MAVLINK for control). We've tried the usual things like firmware updates, resetting all parameters, etc, but it won't seem to register the SBUS connection.

Is there something different with the v2 like requiring the signal to be inverted, or could there something wrong with this particular unit?

Appreciate any ideas anymore might have like a parameter that could be wrong!

Thanks!
Ansel

Ansel Misfeldt · 20 Dec 2024, 20:44

I did more digging and it seems that the problem is related to the v1.14+ firmware I upgraded it to (from the Flight Core v2 downloads). For some reason in recent firmware updates it breaks the SBUS input.

I verified this by also upgrading a working VOXL Flight and was able to reproduce the same problem with the upgraded firmware in 1.14 and 1.15.

Any idea why this would break on the latest firmware releases?

Alex Kushleyev · 3 Jan 2025, 17:22

@Ansel-Misfeldt , I don't think that we are aware of the issue - can you please let us know what is the latest version of PX4 firmware for Flight Core / Flight Core V2 that has working SBUS input based on your testing?

Thank you

Alex

Ansel Misfeldt · 3 Jan 2025, 17:22

@Alex-Kushleyev It was working on v1.11 for certain, and I recall it was working on v1.13 too, but seemed to stop working on v1.14+ from what I recall. We flashed them to different versions many times during troubleshooting and we weren't taking specific notes on which versions it was working on.

Let me know if you need us to test the specific version it breaks on.

Zachary Lowell 0 · 6 Jan 2025, 18:10

@Ansel-Misfeldt said in SBUS not detected:

Let me know if you need us to test the specific version it breaks on.

Reply

@Ansel-Misfeldt will flash a flight core and let you know what we find.

Zach

teddy.zaremba · 7 Jan 2025, 22:13

Hi @Ansel-Misfeldt we're able to get our SBUS radios talking on 1.14 and 1.15.

Could you verify that your radios are bound and that you have the following parameters set on PX4?

Also if you could verify your wiring is setup correctly. RED (power), BLACK (ground), YELLOW SBus RX:

Ansel Misfeldt · 8 Jan 2025, 17:30

@Zachary-Lowell-0 Got it working. It seems we encountered a documented bug where the defaults were somehow getting incorrectly set to the wrong parameter for RC input protocol when we reset the board to firmware defaults. We were checking the COM_RC_IN_MODE but had always had the RC_IN set to Auto previously. This made everything look fine until it glitched and changed the parameter without us knowing.

In case anyone else runs into it, here is the bug: https://github.com/PX4/PX4-Autopilot/issues/22986

Appreciate the assistance on figuring this out Zachary, we can switch over to Flight Cores and VOXL Flights for this client now which they'll be happy about.