Frame IMU Issues
  • A while ago I bought the alexmos standard gimbal controller, with dual IMUs. I've just got it hooked up to my gimbal, and i'm having some issues. The frame and camera IMUs seem to combine their values, and so the controller is just getting garbage data from the sensors. I read the documentation and learned of the ADDR bridge, however on my Rev.B IMU it is not a thin line, but more of a thick pad. I cut the ADDR line, yet this has made no difference. I think the issue is that both IMUs are being interpreted as 0x68 rather than one being 0x68 and the other being 0x69. Is there something obvious i'm missing here? The other thing is that I accidentally lost the splitter that was provided, so I spliced and soldered both IMUs into one line. If I just use one of either IMU, they work flawlessly. The issue is only when using them both together.

    Thanks Guys!
  • So I've been working on this problem and have discovered something interesting. I can get both IMUs to function perfectly, however it required me soldering a 33nf capacitor between the 5v and GND lines on the i2c line, connecting the gimbal to the basecam software, checking i2c high speed, writing to board, then unchecking i2c high speed and writing to board. Once this final write is done, the board works perfectly. However, on a full board restart (unplug/plug in) it goes back to reading both IMUs as the same (0x68) and another i2c high speed cycle is needed to get it to work again. This feels like odd behaviour? I'm sure there is something that I'm missing.
  • You have too many things going on. You just need correctly addressed IMUs and reasobable length I2C cables running separate from other cables, and it will work.

    Note, some boards have build in IMU.
  • Hello,
    I guess that both IMUs still has the same I2C address, and when you turn I2C to high speed, one IMU does not work (may be because of cable length or so). Ensure that you actualy cut the ADDR line on one IMU only, and leave it on the other.
    Also note that some boards (not basecam but made by license) have on-board IMU connected to the same I2C line, so it may cause conflict in addressing. In original basecam boards, on-board IMU is located on a different I2C line so does not interfere with external IMUs.
  • I have the same issue. I can't get the proper addres to second IMU. I there a board scheme to findout and measure the connections?