GY-91 // MPU-9250 + AHRS ... here come troubles!

Hello everyone,

I'm looking to understand what is expecting the Adafruit AHRS library ?
I need to know what are the input units and ... what is the correct sensor calibration ?
What should be the offsets/bias/scale factors/etc ...
Sensor is already working, I can gather data from it using SPI @ 20 Mhz easily.

Thanks for your inputs :slight_smile:

That information is in the sensor data sheet.

What should be the offsets/bias/scale factors/etc

Follow this tutorial for the accelerometer and magnetometer: Tutorial: How to calibrate a compass (and accelerometer) with Arduino | Underwater Arduino Data Loggers

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Thanks @jremington ,

Seems like what I want to achieve might be pretty hard ...
I'm actually looking to onboard a MPU9250 inside a project for an ultra light aircraft as a tracker for orientation and applied Gs (Ex. : when there is a hard landing).

Calibrating this kind of sensors should be done in the final environment which seems a little bit tricky to do it in a plane.
Anyway, I know there are devices from Garmin that do the same but without the need of calibration each time and/or over time ... which definitely seems strange to me right now after reading your link.

Do you think there is a way to do something about that or is it totally impossible based on the limitations of the IMU/MPU ?

Thanks for your time.

You will find that those are not very accurate.

Accurate calibration of the MPU-9250 requires some effort, but is not difficult. If you do the calibration outside of the "ultralight", mount the sensor as far as possible away from any magnetic or iron containing objects, and it should work OK.

Github link to working AHRS for the MPU-9250 (the Sparkfun and Kris Winer versions give totally erroneous results): GitHub - jremington/MPU-9250-AHRS: Arduino Mahony AHRS, includes magnetometer and accelerometer calibration code