I have an MPU9250 IMU sensor (namely this board: 9DOF Razor IMU M0) that I am using to measure orientation.
I want to use the MPU's Digital Motion Processor (DMP) to compute the orientation based on its measurements. Now I need to transfer the computed data to the Raspberry Pi over I2C, and this is where I am having difficulties.
9DOF Razor IMU M0 Code:
#include <Wire.h> #include <SparkFunMPU9250-DMP.h> #define SerialPort SerialUSB #define SLAVE_ADDRESS 0x08 uint8_t data_to_echo = 0; MPU9250_DMP imu; bool run_imu = true; void setup() { SerialPort.begin(9600); Wire.begin(SLAVE_ADDRESS); Wire.onReceive(receiveData); Wire.onRequest(sendData); if(run_imu){ if (imu.begin() != INV_SUCCESS) { while (1) { SerialPort.println("Unable to communicate with MPU-9250"); SerialPort.println("Check connections, and try again."); SerialPort.println(); delay(5000); } } imu.dmpBegin(DMP_FEATURE_6X_LP_QUAT | // Enable 6-axis quat DMP_FEATURE_GYRO_CAL, // Use gyro calibration 100); } } void loop() { } void receiveData(int bytecount) { for (int i = 0; i < bytecount; i++) { data_to_echo = Wire.read(); } } void sendData() { Wire.write(data_to_echo); } Behaviour:
When run_imu = false, the i2cdetect -y 1 detects two devices on the I2C bus - 0x08 and 0x68 and I am able to echo bytes back and I would hope that the same will keep happening when I turn the IMU and DMP on. However, after setting run_imu=true, the only device on the I2C bus seems to be the MPU9250 and I cannot send bytes to the MCU. (I get the OSError: [Errno 121] Remote I/O error as the device with the address 0x08 is not present on the bus)
Problem:
I was able to send bytes back and forth between the SAMD21 processor (which is on the 9DOF Razor IMU M0 board) and the RPi. However, when I turn the imu on (by calling imu.begin()) I am no longer able to communicate with the MCU, and the only I2C address shown by i2cdetect -y 1 is the MPU's 0x68.
I am guessing it has to do something with the fact that the MCU and MPU9250 also communicate using an I2C bus and imu.begin() registers the MCU as a master wrt. to the MPU and therefore it cannot serve as a slave to the RPi - am I right?
Question:
Is there a way how the 9DOF Razor IMU M0's MCU can send data from the DMP over I2C to the Raspberry Pi? Ideally I would like to be able to something like:
. . . void loop() { // Check for new data in the FIFO if ( imu.fifoAvailable() ) { // Use dmpUpdateFifo to update the ax, gx, mx, etc. values if ( imu.dmpUpdateFifo() == INV_SUCCESS) { // computeEulerAngles can be used -- after updating the // quaternion values -- to estimate roll, pitch, and yaw imu.computeEulerAngles(); // Sending the orientation to the RPi using I2C, something like: Wire.write(imu.roll); Wire.write(imu.pitch); Wire.write(imu.yaw); } } } . . . Any tips or ideas on how I might go about transferring the data from the DMP over I2C to the Raspberry Pi are highly appreciated - Thanks!
