drivers/optical_flow/paw3902: backup scheduling to fetch 0 flow

[dagar]

• this sensor provides a MOTION interrupt used for default scheduling, but we also need to publish zero flow information if it's valid

The core issue here is that if there isn't motion we don't have a mechanism to know if the current 0 flow readings aren't stale.

[AlexKlimaj]

Do we need to update the PAA3905 driver to match?

[dagar]

Do we need to update the PAA3905 driver to match?

Yes if this checks out.

[AlexKlimaj]

Hard to tell if its better. It was always slowly yawing to the north.
https://review.px4.io/plot_app?log=9b65dc13-87f4-44e3-84ea-285e25a9a017

Did a mag cal and this is slightly better. Still has the bug where it slowly descends until it lands.
https://review.px4.io/plot_app?log=26a34e80-6518-4130-9456-0fd60d24b7e3

I can see it now will publish 0,0 pixel flow.

[AlexKlimaj]

This is definitely better. This PR on the FC and ARK Flow. EKF_HGT_REF set to baro.
https://review.px4.io/plot_app?log=4c2f02a3-dcba-481d-bde7-60952adc7158

There are times in a hover where the gyro noise causes a 0 flow value to have a compensated velocity. I wonder if we want to ignore the gyro when the pixel flow is 0?

[AlexKlimaj]

Added logic to only compensate when pixel flow if non zero and it flies great. I'm current doing it if either pixel flow value is non zero to compensate both axis. But it might be better to do it per axis?
https://review.px4.io/plot_app?log=19493eb4-0c0f-44a9-a17e-06bbb7af9f83

[bresch]

Great, that much better than before, the position is now rock solid while hovering.
Tested indoors on a QAV250: https://logs.px4.io/plot_app?log=ffa07b2c-fd47-4a0e-89c1-71f5d348ed2f

[bresch]

@AlexKlimaj I'm not sure if adding this logic is really necessary, the gyro noise should be centered around 0 so it isn't an issue. Did you see an improvement by adding that conditional gyro compensation? (I flew with it and it worked well, but I didn't try without)

[DronecodeBot]

This pull request has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/optical-flow-oscillating-position/34470/2

[DronecodeBot]

This pull request has been mentioned on Discussion Forum for PX4, Pixhawk, QGroundControl, MAVSDK, MAVLink. There might be relevant details there:

https://discuss.px4.io/t/holybro-optical-flow-sensor-thoneflow-oscillations-on-main/34768/1