Have just been alerted by another Pixhack owner that in AC 3.5.0 the second onboard compass is no longer recognised whereas it was fine in AC 3.4.6.In looking back over a few logs it seems this is correct.Despite disabling the third compass it was recognised as can be seen in the parameters.This is no biggy for me as two compasses are plenty but it does mean something went wrong in the transition to 3.5.0. and it no longer sees this bit of hardware.
CUAV Pixhack V3
**AC 3,4,6 **
PARM, 52446178, COMPASS_DEV_ID, 73225
PARM, 52446206, COMPASS_DEV_ID2, 131874
PARM, 52446274, COMPASS_DEV_ID3, 263178
AC3.5.0 with different primary compass.
PARM, 248385139, COMPASS_DEV_ID, 466441
PARM, 248385174, COMPASS_DEV_ID2, 131874
PARM, 248385207, COMPASS_DEV_ID3, 0
This also showed up in my recent calibration video with only two green bars active during it.