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MPU-9250 instead of MPU-9255?
#21
I don't think it's the auto calibration.

The screenshot is very strange behavior, I have not seen. Does it do this with both sensors?

I have found a problem that gives bad data from the imu when the ram is full and the kernel is swapping. Not sure how I will deal with this, but it is not normally a problem for autopilot.
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#22
just curious is there something close to the imu, fan, disk drive, speaker or some other EM source that could interfere .
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#23
it would be easy to find out by running the scope on the compass output, then moving the fan wires or other possible sources around.
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#24
(2018-07-29, 01:14 PM)seandepagnier Wrote: it would be easy to find out by running the scope on the compass output, then moving the fan wires or other possible sources around.

No there is nothing around that could disturb the IMU.
The IMU stays stable for a while, and than suddenly starts misbehaving.
   

As you can see on the picture above, it is not only the magnetic compass, but also the pitch and heel.
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#25
I have not seen that, but I have seen sensors with broken axes, and extreme biases.

Could you try a different sensor?
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#26
(2018-07-30, 07:45 PM)seandepagnier Wrote: I have not seen that, but I have seen sensors with broken axes, and extreme biases.

Could you try a different sensor?

I dus. The third one was ok :-)

If you want to investigate it, I can send it to you...
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#27
(2018-07-24, 02:48 PM)seandepagnier Wrote: If it works with openplotter it should work with tinypilot because the driver is the same.

There is a bug in tinypilot that if you change to a different sensor, it won't work.  If you delete RTIMULib.ini it will work again.  I will correct this soon, I am currently working on supporting more sensors.   the library may technically detect them and give data, but many sensors need to calibrate the accelerometer bias unlike mpu925x.

The new mpu9255 with orange (not yellow) capacitor also need accelerometer bias calibrated, so beware of this.  Currently I have some that have bias so far wrong (more than 1 g)  that they saturate the 2g range even when perfectly still.   This needs additional work to automatically switch to 4g range in the driver, and will lose a bit of precision (which should be ok)

So at the moment I suggest only mpu9250/mpu9255 with yellow capacitor or otherwise factory calibrated accelerometer (range .098 to 1.02 g)   but I will support other sensors soon, and it requires additional calibration for accelerometer bias.

Is this still a issue? I was using the MPU9255 with orange capacitor with no problems now I received the MPU9255 with Yellow capacitor when I swap it says error compass or gyro failure.

Deleting RTIMULib.ini did not help
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#28
   

I have tested these 3 types the number in green or red is what I bought (do not know if it is what I bought?) 
Red did not work , green did work.
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#29
5-10% of these are completely defective in one way or another and cannot be used

another 20-40% of these have compass sensor with very large bias, or accelerometer with too large bias that saturates the 2g range so degrades performance

I discard these sensors and almost half are rejected.
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#30
I would recommend the following IMU if it does not interfere with your current use of pi pinouts.

Used to be 12US now they are 20 bucks

amzn link
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