MPU9250 and LSM9DS1
Navio2 contains two 9DOF (degree of freedom) IMU: MPU9250 and LSM9DS1. Each of them combines a gyroscope, an accelerometer and a magnetometer in one device. IMU sensors are not only popular as a part of drone autopilot projects, but are also widely used in devices like cellphones, tablets, etc.
If you have not already done that, download Navio2 drivers and examples code here.
IMU example for Navio2 runs with one of the on-board sensors at a time. During start-up program you have to specify with which sensor to work.
If you have not build the examples yet, perform the following commands:
To check the IMU example, you need to run this command:
./AccelGyroMag -i [sensor name]
Move to the folder with the source code, compile and run the example:
python AccelGyroMag.py -i [sensor name]
[sensor name] allows you to choose inertial measurement unit:
mpu is MPU9250,
lsm is LSM9DS1.
LSM9DS1 driver is currently not implemented. Use the C++ counterpart.
You should immediately see 9 values, updated in real time. Try to move the device around and see them change. They include Accelerometer, Gyroscope and Magnetometer data, three axis each.
Connection established: True
Acc: +0.014 +0.139 +9.974 Gyr: -0.042 +0.022 +0.011 Mag: -3525.450 +29.584 +0.000
Acc: -0.010 +0.268 +10.036 Gyr: -0.042 +0.019 +0.015 Mag: -14.963 +43.390 -50.130
Acc: -0.010 +0.278 +9.888 Gyr: -0.043 +0.021 +0.012 Mag: -16.566 +42.852 -50.302
Acc: +0.010 +0.187 +10.041 Gyr: -0.039 +0.021 +0.011 Mag: -14.963 +42.314 -50.817
Acc: -0.062 +0.158 +9.855 Gyr: -0.039 +0.020 +0.011 Mag: -15.497 +42.493 -49.959
Acc: -0.067 +0.196 +10.056 Gyr: -0.044 +0.020 +0.013 Mag: -14.963 +43.748 -50.130
For further information, see source code.
create_inertial_sensor() creates object of class MPU9250 or LSM9DS1 depending on the argument passed to the program.
The next thing we should pay attention to is the line
sensor->initialize(), as it does an important job of setting internal device parameter. Note that this function also sets scales for both Accelerometer and Gyroscope (and for Magnitometer in case of LSM9DS1).
The main function loop is pretty straightforward: read the data, print the data.