Pressure sensor noise filtering on APM1 shields

I have 3 APM1 shields, of which only one is usable due to excessive noise on the pressure sensors of the other two. This noise appears to be stochastic (ie random, with a mean of 0), therefore it should be easy to remove with a simple filter. I searched through the PARAM list of AC3.01 and I find no parameter that controls filtering on this sensor, which I find very strange given how noisy they were when the APM1s first came out.

My question is: has anyone tried a custom fix for this problem? It would be sad to have to chuck these APM1s out, since I have got AC3.01 working nicely on my other APM1. However the way they are now it is impossible to reliably use altitude hold, which is also required for any of the autonomous modes too.


Johnny I don’t know quite how to break it to you but one day soon you are going to have to let go of those V1 boards. It sounds like you are pushing them though, well done.

Hi Johnnybravo,
The baros on the APM 1 never performed as well as they were supposed to and they are extremely sensitive to light. :frowning:
They do need to be well covered at least by a piece of light darkening foam.
But basically you are dealing with a no longer supported board for at least the last 6 months or so.
I would strongly urge you to move into the new Pixhawk camp which should be good for at least another couple of years,
At this point the APM 2, 2.5 and 2.6 will be supported with current features for another year or so, but they are unlikely to have many new features added to them because both performance wise and memory wise they are pretty well maxed out.
There will probably still be a few improvements, but basically all the new stuff will be on the Pixhawk.
Best Regards,

Guys, thanks for the replies. I do have an APM2.5 and I intend to get a PixHawk, I’m mainly using the old APM1 boards for testing purposes. I realise they are outdated now, quite considerably, and I won’t attempt certain things that strain the processor such as autotuning. But knowing I can put them in a cheap frame and do range testing on autonomous flights, video feeds etc is reassuring.

My suggestion re the filtering is because I realised that if the noise is stochastic, a simple exponential moving average filter - with just one parameter - could be a real low cost workaround. I’m not much of a coder so I won’t attempt to patch it myself, but I figured that someone else may have attempted it.

I’ll take the advice and do the light-sensitivity workaround. Its summer here in Africa and very bright in the day :smiley: