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IMU axis/orientation
  • icecream
    hi all

    just wondering about IMU orientation

    mine looks very much like this:

    https://cdn-aerialpixelscom.netdna-ssl.com/wp-content/uploads/2014/01/P1180384.jpg

    i'm intending on mounting the IMU such that the printed side (as pictured above) is effectively attached to the bottom of the camera. from my understanding, this should correspond to Axis TOP = Z, however this seems to result in the pitch axis being upside down. so am i misunderstanding or is this item printed incorrectly?
  • 200sx
    I think you try reverse the z to -z. In the GUI you can change the values. If it works, the it's printed wrongly
  • icecream
    yes this does work. perhaps the print is meant to be interpreted as if printed on top. strange.

    one other thing i've noted is that when axis top/right = -Z/-X, it is impossible to successfully calibrate the accelerometer. it just keeps returning "accelerometer is not calibrated" after attempting to calibrate (and beeping is different). not an issue for me but possibly a bug so thought i'd just note it (i'm running 2.4b7 8bit 3axis).

    thanks
  • OctovisualsOctovisuals
    Yeah, mine is mounted with the printed side upwards and it's -Z in the GUI/firmware.

    I think this should be explained properly in the manual in the first place...

    Anyway, just as 200sx said, just mount it the best way (tight and paralled to the axes) and configure the software accordingly.

    Don't forget to do the 6-point calibration first.

    Best regards.
  • Garug
    On this document http://www.invensense.com/mems/gyro/documents/PS-MPU-6000A-00v3.4.pdf page 40 shows the axis in relation to the IC. The positioning dot is really small on the IC, but it is there.

    Page 43 speaks about orientation error. I do not find how accurately the axis are aligned inside the IC, but I suppose then they are aligned so accurately we do not need to care about that. It is then this misalignment of the IC installation that we are trying to calibrate with 6 point calibration.

    My advise is not to perform 6 point calibration before everything is working reasonably well. After everything is reasonably well working, there is a reference to witch it can be compared if 6 point calibration improved anything. I guess it could also make things worse if not performed accurately.
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