Member Since: February 3, 2014

Country: United Kingdom

  • I’ve just purchased a Razor-IMU board and have had great success getting it working - fabulous little IMU platform.

    Firstly, I apologise if this is the wrong place to ask this question but there seems to be an active community. If this is not the correct place, I’d be grateful for a better link.

    What I’m trying to do now is to run the Razor-IMU firmware on an ARM platform (Cortex-M4) using the same 3 sensors as present on the Razor (ADXL345, HMC533L, ITG3200). I’m struggling to get the code working as well as the Razor works and I believe my main issue is the orientation of the sensors on my custom PCB - I can’t for the life of me figure out whether I need to invert axes or swap them around. I’d be really grateful of some help with this, I’ve Googled in regards to sensor orientation but I just can’t get my head around it.

    My board axis has X going horizontally, Y vertically with Z down (NED, I guess). The accelerometer is positioned so that the +X axis points west, +Y points south and +Z points down. The magnetometer has its +X axis pointing west, +Y pointing south and +Z pointing down. The gyro might be where I’m getting confused - the +X axis runs horizontal (according to the right-hand rule) with turns towards south being positive, +Y runs vertically with turns towards east being positive and counter-clockwise rotations on Z are positive.

    With reference to the Razor IMU firmware, how would I then map my axis orientations into the firmware? I seem to have tried all combinations but I still have a very unstable system - when I rotate the sensor, observing the yaw, pitch and roll, the yaw always seems to return to an initial value. Its driving me mad!!

    Thanks in advance to anyone who can help.

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