OpenCR 1.0 IMU configuration

Sarwan · December 3, 2020, 10:22am

Hello,
I would like to change the register of the IMU in openCR 1.0 board. Currently, the accelerometer is set to 8g and gyroscope is set to ±2000 deg/sec. I need to set those values to 2g and ±250deg/sec.

I have gone through the MPU9250 cpp file and got the implemented values.

Kindly inform me how it can be done.

Thanks a lot

willson · December 8, 2020, 7:50am

Hi @Sarwan
You’ll need to modify the below IMU source code in order to do that.
Please refer to Gyroscope Configuration and Accelerometer Configuration sections of MPU-9250 datasheet.

github.com

ROBOTIS-GIT/OpenCR/blob/31eb2cc24a85f510507654fd7815ff2e41adb5a1/arduino/opencr_arduino/opencr/libraries/IMU/MPU9250.cpp#L119


      
          	delay(1);

          	imu_spi_write(MPU9250_SPIx_ADDR, MPU9250_INT_ENABLE, ENABLE);

          	delay(1);

          	//MPU9250 Set Sensors

          	imu_spi_write(MPU9250_SPIx_ADDR, MPU9250_PWR_MGMT_2, MPU9250_XYZ_GYRO & MPU9250_XYZ_ACCEL);

          	delay(1);

          	//MPU9250 Set SampleRate

          	//SAMPLE_RATE = Internal_Sample_Rate / (1 + SMPLRT_DIV)

          	imu_spi_write(MPU9250_SPIx_ADDR, MPU9250_SMPLRT_DIV, SMPLRT_DIV);

          	delay(1);

          	//MPU9250 Set Full Scale Gyro Range

          	//Fchoice_b[1:0] = [00] enable DLPF

          	imu_spi_write(MPU9250_SPIx_ADDR, MPU9250_GYRO_CONFIG, (MPU9250_FSR_2000DPS << 3));

          	delay(1);

          	//MPU9250 Set Full Scale Accel Range PS:2G

          	imu_spi_write(MPU9250_SPIx_ADDR, MPU9250_ACCEL_CONFIG, (MPU9250_FSR_2G << 3));

          	delay(1);

          	//MPU9250 Set Accel DLPF

          	data = imu_spi_read(MPU9250_SPIx_ADDR, MPU9250_ACCEL_CONFIG2);

          	data |= MPU9250_ACCEL_DLPF_41HZ;

          	delay(1);

The Accelerometer is already set to 2G in the line 124.

Please note that recent OpenCR comes with ICM-20648 instead of MPU-9250 due to the EOL of the sensor.
Thanks.

Sarwan · December 14, 2020, 6:21pm

Thanks a lot. I would like to read PPM signals from a receiver.

For this purpose I used the above-mentioned library in Arduino Uno.

I am new to programming. Could you please inform me , how to use the library for openCR board.

Kindly suggest to me a learning resource to do it , if it requires too many changes.

Thanks

willson · December 30, 2020, 12:59am

Looks like the developer has left a detailed instruction on how to use the library.
Download the library and copy it into the Arduino library directory, then append the #include <PPMReader.h> in the beginning of your code to use the PPM-reader.

If you are using Windows, Arduino library directory can be found from C:\users\<YOUR_ACCOUNT>\Documents\Arduino\libraries