lib/battery: fix duplicate uORB publish and minor cleanup

[dagar]

While debugging I noticed battery_status was publishing at 200 Hz.

[dagar]

We need to be careful that the pub freq matches the configured filter freq.

Yes I'm pretty sure that's wrong for most of the cases outside of the typical NuttX boards. Maybe we could add an update method to AlphaFilter that passes the timestamp or dt.

FYI @MaEtUgR

[dagar]

[MaEtUgR]

Maybe we could add an update method to AlphaFilter that passes the timestamp or dt.

The Alpha filter has an update function setParameters() but in #14551 I was explicitly asked to not measure dt on every loop iteration for performance reasons. My conclusion was that battery update frequency needs to defined compile-time and that's why it's passed to the Battery class constructor.

[dagar]

My conclusion was that battery update frequency needs to defined compile-time and that's why it's passed to the Battery class constructor.

That's mostly true (probably all the NuttX boards you've used), but like quite a few other things in PX4 it unfortunately isn't that simple. I faced similar problems with drivers and the sensors pipeline, ultimately deciding to gut all the fixed rates we thought we knew and actually measure it in the consumer.