Calibrating Devantech cmps03

[westaust55]

Hello eagleslg,

I am having seemingly similar problems with a Devantch CMPS03 compass module.
Initially it was working and headings were accurate without needing to calibrate.
I disconnected the CMPS03 while I worked on some other hardware but when I returned to using the CMPS03 I found that the readings returned via the i2c bus are inaccurate.
The readings in (in 2-byte mode) no longer cover the full range from 0 to 3599 but vary from around 600 to 2700 varying gradually up and down in two cycles for a single 360 degree turn.

The values I am getting are as follows (rounded a bit):

compass...1-byte 2-byte
direction...value...value
N............060.....0850
NE..........191.....2700
E…........182.....2560
SE..........171.....2410
SES........085.....1200
S….........087.....1230
SW........092.....1300
W…......073.....1020
WNW.......056.....0788
NW........060.....0850
I am therefore very interested in what you did/found that finally resulted in your compass working correctly as I may have the same mistake/problem.