It works!!! 
So I can definitely say that there are remains of an RTIMU lib in the system.
You need to remove all the RTIMUlib files in usr/lib/... but ALSO all the python files hidden everywhere (usr/lib/python2.7, usr/lib/python3.4, usr/lib/python3 , also in usr/local/lib/python/...).
After what I reinstalled RTIMU (and I added python3 setup.py install).
Now when I open openplotter, the good file is created, also with the i2c-detect.py creating "detected-....ini". The value of the magnetic heading and the pitch are now visible and working in SignalK. (But they (+temperature + pression + humidity) are not send to NMEA183 at the moment, only GPS data
)
@sailoog : I would be you, I would maybe generate a new NOOB without the corrupted old files. That is maybe why you say that RTIMULib is not stable. And it would speed up the process of reinstalling the system after some experimentation.
So I can definitely say that there are remains of an RTIMU lib in the system.
You need to remove all the RTIMUlib files in usr/lib/... but ALSO all the python files hidden everywhere (usr/lib/python2.7, usr/lib/python3.4, usr/lib/python3 , also in usr/local/lib/python/...).
After what I reinstalled RTIMU (and I added python3 setup.py install).
Now when I open openplotter, the good file is created, also with the i2c-detect.py creating "detected-....ini". The value of the magnetic heading and the pitch are now visible and working in SignalK. (But they (+temperature + pression + humidity) are not send to NMEA183 at the moment, only GPS data
)@sailoog : I would be you, I would maybe generate a new NOOB without the corrupted old files. That is maybe why you say that RTIMULib is not stable. And it would speed up the process of reinstalling the system after some experimentation.