> I'm using a BMP581 barometric pressure sensor on my custom flight computer designed for a rocket project. The altitude data I read from the sensor is not stable over time. While the sensor is in a stationary position (not moving), the altitude value sometimes slowly decreases, reaching values like -70 meters, and then slowly starts increasing again.
As said, this sensor measures barometric pressure - not altitude. The altitudes are your interpretation.
First, I suppose you know that barometric pressure is not constant. In fact, it can vary significantly in the very same location over the day. To interpret a barometric pressure as altitude, a very recent calibration to the local pressure is essential. And essential means before every single use.
Secondly, I have dealt with the BMP280, which has a quite elaborate calibration process. I assume the BMP580 is not dissimilar. But for a proper calibration, your measuring hardware must have reached thermal equilibrum. As it sounds, some of your boards do not - otherwise values wouldn't drift so much. Or, as noted below, the supply voltage drifts.
>The first one has the same problem even though I removed the components L8 and C31 instead of keeping them.
I have no idea what you are talking about.
If you refer to a specific board, show us the schematics, or a link to it.
Although from the component names, I don't think they can influence pressure readings in any way directly.
> This issue does not occur when I test with last year's flight computer using the same sensor model, so I'm trying to understand whether this is a hardware-related issue (power supply, layout, noise) or if something in my software or configuration could cause it.
Thus your assessment as "bug report" is very rushed.
Perhaps an electrical issue like supply voltage drift or thermal problems. Or a change in design regarding air flow direction and orientation.
