What to do if one of the output channel in pixhawk is not working

I am facing problem where the channel five of the pixhawk is not working,
and also I cant see the motor parameter on the qground control

Help is appreciated.


@mittalpathare I just responded to your support e-mail. It is most likely a bad PWM out on the Pixhawk and we will have to send a replacement.

Hey @kklemens/BlueROV gang,

I also just had a similar problem on a current build and thought I should report it as it was weird and also definitely didn’t/doesn’t require sending out a new Pixhawk…

It’s a heavy setup so I’m using all 8 output channels. As with the original post, the problem I had was with output channel 5. Strangely, everything was working fine, but I realised that I had to update the companion software (0.0.17 - > 0.0.31) and also had to work on another problem which required disconnecting all the ESCs (one of the lessons of this tale is to only troubleshoot one issue at a time!) Once all the ESCs were reconnected I ran a motor test and #5 was unresponsive. I checked all the ESC connections as I thought I might have rewired badly but couldn’t see any issues. I then swapped the connections for motors 4 and 5 around on the pixhawk. That got motor #5 working and #4 stopped, isolating the problem to the pixhawk itself or the software/settings, which I thought unlikely. However, I went into the SERVO menu of the parameters section of QGC and lo-and-behold, servo 5 was coming up as “disabled”. I selected motor 5 and voila, back in action.

No idea why that servo would have been turned off - I was previously unaware of the SERVO part of the parameters, so I hadn’t been in to that menu myself and turned something off. Best guess is that it was something to do with the companion software update? So i thought you all might want to know for future development etc.

In terms of the version that I flashed to the SD card: I got the link for that from this forum yesterday (No companion update button available - #42 by bjcresswell) but it’s worth noting that there are various links to “update” the companion software. Might be worth going through older threads and deleting old links or pointing them all to one “master” software update page?? Sure you guys are engaged with this, but just an observation from an end user.

Let me know if you want any more info on this.



Hi @bjcresswell, thanks for the heads-up on this, I’ve passed it on to the other members of our support team :slight_smile:

Not sure how the SERVO output could have been set to disabled without direct user input, since parameters generally aren’t set automatically - that’s definitely odd. Perhaps worth noting that the reset parameters to defaults functionality in QGroundControl can be used if the Pixhawk starts acting weirdly.

Given you flashed the SD card directly there was no update script that could have potentially changed something, so I’m not sure that’s a possible cause. If 0.0.31 was setting a parameter on startup it should happen every time to everyone, which isn’t the case. That said, I don’t know what did cause it, so it’s at least something we know has happened now, and can try to keep an eye out for in case it comes up again some time.

Fair point, although that’s something of a bandaid fix for the underlying issue that “it should be obvious how to update the software correctly”. As I understand it most of the links are to a documentation or website page, which should have the latest information or automatically redirect to somewhere that does. Direct download links tend to be of custom temporary versions that fixed a specific issue, and generally we expect that the context there will discourage people from using them, especially if they’re old links. If and when that kind of thing gets attempted by mistake it generally doesn’t work anymore, which either leads to the relevant documentation being found, or a question on the forum/to our support email asking how to fix the issue.

Conveniently, the existing companion software is in the process of being replaced with a version that is very different, and requires flashing to upgrade to, so we effectively get a fresh start. We’re also in the process of replacing our docs system and structure, along with various other changes that should improve information accessibility (e.g. I’ve just added a Software and Firmware section to our work-in-progress Technical Reference) :slight_smile:

Hey @EliotBR, thanks so much for the speedy and thorough response! It definitely seems like an anomaly, so am glad you guys have it on record, just in case…

I did also note in your response to my other related query (software update) that you mention there was a specific issue with the update process from 0.0.17 and I just thought I’d better highlight that the ROV I’m working on was purchased from you guys last August, so there’s clearly still old software going out on current hardware. I imagine it was just one that fell through the cracks, but might be something to keep an eye out for, although it also looks like you are on the brink of deploying some nice shiny new software which I look forward to trying :slight_smile:

Thanks again,


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We had some hold-ups last year with keeping our vehicle production process in line with our software updates. That’s since been rectified, although we’re still working on improving the process to minimise that turnaround.

Indeed. The original Companion software was a decent first attempt at the functionality that’s been required over time, but because it was built up incrementally and without precedents it’s not structured amazingly for what it needs to do now, and is a bit unwieldy to work with/extend. The replacement takes our learnings from the first one to create a more modular and expandable structure, which should be easier to use on a variety of devices, and more robust when operating and granular when updating.

We’re definitely excited for the new structure and direction, particularly because it should be significantly easier for users and third-parties to develop their own extensions and additions, while also being easier for us to maintain and improve the core functionality :slight_smile: