Normally, there's no need to calibrate the IMU by the user. If the 
LED blinks Green quickly of motion detection when it is stationary 
on the ground, please try basic or advanced calibration according
 the sensor mod value.
1.  Gyroscope 'mod' value normally is [0.0, 1.5], if it's at the range 
    of [1.5, 3.0], please do basic calibration, if it's larger than 3.0,
    advanced calibration is needed;
2.  Accelerate 'mod' value normally is [0.98, 1.02], if it's at the 
    range of [0.97, 0.98] or [1.02, 1.03], please do basic calibration,
    if it's less than 0.97 or larger than 1.03, advanced calibration 
    is needed; 

The Compass (raw) shows raw data of the magnetic vector, and the
 normal range is from -500~500. The ‘mod’ shows the calibrated 
data modulus of magnetic vector, and it could be used to check the
 calibration effect. If the mod value is below 750 or beyond 2250, 
you should check whether there is magnetic interference or not. 
If yes, clear them and recalibrate. If not, but the ‘mod’ value is still 
out of normal range after recalibration, try to use a magnet (<3cm 
away from the compass) to orbit the compass module (on two 
horizontal axis and one vertical axis) several laps to degauss the 
compass, since it may be magnetized. After degaussing (Tip of 
Other-ERR[27] disappears on the software), do recalibration.