Lab 22 - MPU9255 Sensor Module

CLASSWORK:

Task: get YPR data off of the MPU:

1. Download the Sparkfun MPU-9250 9 DOF IMU Breakout Library from the Arduino IDE's Library Manager. Make sure the author is Sparkfun Electronics and that it says Version 1.0.0.
2. Go to Examples and open up the MPU9250BasicsAHRS code.
3. Wire up the sensor to the Arduino: VCC to 3.3v, GND to GND, SDA to A4, SCL to A5.
4. Upload the sample code to the Arduino.
5. Open up the Serial Monitor to see the data streams.

Simplified MPU 9250 sample code (w/o YPR data)

#include "MPU9250.h"

MPU9250 myIMU;

void setup()

{

 Wire.begin();

 Serial.begin(38400);

 myIMU.MPU9250SelfTest(myIMU.SelfTest); // Start by performing self test and reporting values

 myIMU.calibrateMPU9250(myIMU.gyroBias, myIMU.accelBias); // Calibrate gyro and accelerometers, load biases in bias registers

 myIMU.initMPU9250(); // Initialize device for active mode read of acclerometer, gyroscope, and temperature

 myIMU.initAK8963(myIMU.magCalibration); // Initialize device for active mode read of magnetometer

}

void loop()

{

 if (myIMU.readByte(MPU9250_ADDRESS, INT_STATUS) & 0x01)

 {

 myIMU.readAccelData(myIMU.accelCount); // Read the x/y/z adc values

 myIMU.getAres();

 // Now we'll calculate the accleration value into actual g's

 // This depends on scale being set

 myIMU.ax = (float)myIMU.accelCount[0]*myIMU.aRes; // - accelBias[0];

 myIMU.ay = (float)myIMU.accelCount[1]*myIMU.aRes; // - accelBias[1];

 myIMU.az = (float)myIMU.accelCount[2]*myIMU.aRes; // - accelBias[2];

 myIMU.readGyroData(myIMU.gyroCount); // Read the x/y/z adc values

 myIMU.getGres();

 // Calculate the gyro value into actual degrees per second

 // This depends on scale being set

 myIMU.gx = (float)myIMU.gyroCount[0]*myIMU.gRes;

 myIMU.gy = (float)myIMU.gyroCount[1]*myIMU.gRes;

 myIMU.gz = (float)myIMU.gyroCount[2]*myIMU.gRes;

 myIMU.readMagData(myIMU.magCount); // Read the x/y/z adc values

 myIMU.getMres();

 myIMU.magbias[0] = +470.;

 // User environmental x-axis correction in milliGauss TODO axis??

 myIMU.magbias[1] = +120.;

 // User environmental x-axis correction in milliGauss

 myIMU.magbias[2] = +125.;

 myIMU.mx = (float)myIMU.magCount[0]*myIMU.mRes*myIMU.magCalibration[0] -

 myIMU.magbias[0];

 myIMU.my = (float)myIMU.magCount[1]*myIMU.mRes*myIMU.magCalibration[1] -

 myIMU.magbias[1];

 myIMU.mz = (float)myIMU.magCount[2]*myIMU.mRes*myIMU.magCalibration[2] -

 myIMU.magbias[2];

 } // if (readByte(MPU9250_ADDRESS, INT_STATUS) & 0x01)

 // Must be called before updating quaternions!

 myIMU.updateTime();

 myIMU.delt_t = millis() - myIMU.count;

 if (myIMU.delt_t > 500)

 {

 // Print acceleration values in milligs!

 Serial.print("X-acceleration: "); Serial.print(1000*myIMU.ax);

 Serial.print(" mg ");

 Serial.print("Y-acceleration: "); Serial.print(1000*myIMU.ay);

 Serial.print(" mg ");

 Serial.print("Z-acceleration: "); Serial.print(1000*myIMU.az);

 Serial.println(" mg ");

 // Print gyro values in degree/sec

 Serial.print("X-gyro rate: "); Serial.print(myIMU.gx, 3);

 Serial.print(" degrees/sec ");

 Serial.print("Y-gyro rate: "); Serial.print(myIMU.gy, 3);

 Serial.print(" degrees/sec ");

 Serial.print("Z-gyro rate: "); Serial.print(myIMU.gz, 3);

 Serial.println(" degrees/sec");

 // Print mag values in degree/sec

 Serial.print("X-mag field: "); Serial.print(myIMU.mx);

 Serial.print(" mG ");

 Serial.print("Y-mag field: "); Serial.print(myIMU.my);

 Serial.print(" mG ");

 Serial.print("Z-mag field: "); Serial.print(myIMU.mz);

 Serial.println(" mG");

 //myIMU.tempCount = myIMU.readTempData(); // Read the adc values

 // Temperature in degrees Centigrade

 //myIMU.temperature = ((float) myIMU.tempCount) / 333.87 + 21.0;

 // Print temperature in degrees Centigrade

 //Serial.print("Temperature is "); Serial.print(myIMU.temperature, 1);

 //Serial.println(" degrees C");

 myIMU.count = millis();

 }

}

HOMEWORK:

Currently, the header file for the MPU 9250 is written such that the maximum acceleration that can be read by the accelerometer is 2g's. Modify the header file so that it allows the MPU 9250 to read a maximum acceleration of 16g's.