Using the BNO055 I find it gives the different heading reading depending on the orientation when I power up.
I'm using NDOF (OPR MODE = 0xC0) & I've calibrated until I get 3 is all the cal status bits (CALIB_STAT = 0xFF). I then save the OFFSET & RADIUS reg to non-volatile ram (regs 0x55 thru to 0x6A). I then power the unit up point in one direction & get (say) 160 degees. I then power off, rotate thru 90 degees & power up again. I then move it back to the original direction & it read 114 degees
I staying in the same place & keeping the pitch & roll very close to 0 degees.
