Compass device id no value

I have two apm2.8 with two neo7m gps.
in both compass_dev_id value is zero for both internal & external compass.( tried both copter 3.2.1 & beta version USING APM PLANNER 2.0)
when connected to qcgroundcontrol says compass_dev_id parameter missing
also, my compass heading is wrong after many attempts


First off, the firmware for the APM supports ONLY ONE compass, so you have to make a choice.

If you connect the external compass and leave the internal compass enabled, APM cannot ‘find’ either compass because they have the same i2c device ID.

Refer to the documentation that came with the board to determine how the internal compass can be disabled.

@oldgazer1 i had removed the mag jumper to disable the internal compass as per the guidelines available on internet.

In the advanced parameter list i have enabled first compass and disabled second, third compass

I think my compass calibration offsets are not getting saved due to no device id

OK, try this:

Disconnect the external compass.
Enable the internal compass.
Run the compass calibration…

Ok will try & tell u

Sir put the mag jumper on for internal compass after removing the external compass.Did caliberation but compass dev id value is zero.
Though the internal compass shows accurate heading the external deosnt show accurate heading

I assume that the compass dev id is required in apm2.8 to save caliberation offset to be saved to that ID.

Few pics

OK, so we know the internal compass works, so let’s disable it and connect the external.

With the external compass connected, connect the APM to Mission Planner.

When the parameter download completes, point the front of the aircraft North.

Watch the Compass Heading and rotate the aircraft Clock Wise (East) 90 Degrees. The heading should move towards 090 degrees. Now rotate the aircraft Counter Clock Wise (West) 180 degrees. The compass heading should follow the front of the aircraft, pass through 000 degrees and move towards 270 degrees.

I did that but the external compass heading shows east when actually pionted north after repeated caliberation.
Checked the mag chip orientation which is upside down and pointing forward ie 180 degrees roll. ( mag chip pin1 dot right and forward direction ie i am sure that compass orientation is ok)

As i armed my quad in open field the heading of external compass was accurate.
Did simple mode in pos hold everthing was ok
Later i would try RTH and super simple mode
Will ping you if any deviation occurs.