External mag on I2C problem on UBLOX NEO-M8N HMC5983 GPS Mod

I have a UBLOX NEO-M8N HMC5983 GPS Module GYGPSV5-NEO from
http://www.banggood.com/NEO-M8N-Flight-Controller-GPS-Module-GYGPSV5-NEO-for-Pixhawk-APM-p-974362.html and the GPS is working nicely. But I do not get the ext. mag on this GPS running correctly.
When I try to calibrate this ext. mag, I do not get any rotation on the calibration screen from mission planner.
Is this ext. mag supported? should it work?

Best wishes