"One more question; other than yaw control, and protection against motor failure, is there any other reason why the top- and underside props would need to behave differently?  In other words, other than the above two, can the upper and lower props be…"

"Thanks - that's exactly what I needed confirming - it does mean I need to think a lot harder about my controller code, and PCB. Hugues said:
The eight motors are controlled individually by their ESC and own PWM signal from the flight controller.…"

"I was about to ask the same question, so I'll share what _I_ think, and hope someone chips in to tell me if I'm wrong.

1 - the compass gives you absolute orientation of your UAV compared to the magnetic north pole - currently somewhere north of…"

"OK, I did a little more testing:
Setting the gyro DLPF to 0, the ADC sampling rate goes up to 8kHz according to the spec.  Then setting SMPLRT_DIV to 31 should mean the data ready interrupt triggers at 250Hz.  But whatever I set SMPLRT_DIV to, I get…"

"Thanks Phillip, useful background

I'll have a go with trying higher frequency dlfp - it makes a lot of sense - I already have lots of code integrating / averaging both sets of sensor readings much like you describe so it should be relatively safe…"

"One (unrelated) questions?  Why set dlpf as high as 250Hz?  I'd always assumed that nearly everything above 10Hz was just going to be prop / motor noise - I'd assumed acceleration due to movement was not noisy once the props / motor noise was…"

"Thanks Phillip,

I tried pointing X and Y axes down, and they did show 1g as expected, so as you say they were fine - after a bit of thinking and digging around, I found a bug in my code that was creating the dead-zone (related to subtracting…"