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9DOF IMU

ICM-20948​

Navio2 Plus contains two 9DOF (degree of freedom) IMU: ICM-20948. 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.

IMU example​

If you have not already done that, download Navio2 Plus drivers and examples code here.

IMU example for Navio2 Plus runs with one of the on-board sensors at a time. During start-up program you have to specify with which sensor to work.

C++​

note

If you have not build the examples yet, perform the following commands:

cd C++
make

To check the IMU example, you need to run this command:

cd Build
./AccelGyroMag -i [sensor name]

Python​

Move to the folder with the source code, compile and run the example:

cd Python
python AccelGyroMag.py -i [sensor name]

Argument [sensor name] allows you to choose inertial measurement unit: icm1 is ICM-20948 on CS 1, icm3 is ICM-20948 CS 3.

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. 

Selected: ICM20948 CS 1
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.

tip

Function create_inertial_sensor() creates object of class ICM20948 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.

The main function loop is pretty straightforward: read the data, print the data.

note

You can find additional information about the chip in ICM-20948 datasheet.