BPI:bit and MPU-9250 Nine-Axis example using the Arduino IDE

In this article we look the MPU-9250 Nine-Axis (Gyro + Accelerometer + Compass) MEMS MotionTracking™ Device which is fitted to the BPI:bit

webduino:bit
webduino:bit

The sensor uses the following GPIO

MPU9250_SCL GPIO 22 Digital Output
MPU9250_SDA GPIO 21 Digital Output
MPU9250_INT GPIO 16 Digital Input

 

Parts Required

Name Link
Banana PI Bit board Banana PI Bit board with EPS32

 

$19.50 for this board is a good price

Features

Lets look at the sensor features from the manufacturer

Gyroscope Features
The triple-axis MEMS gyroscope in the MPU-9250 includes a wide range of features:

  • Digital-output X-, Y-, and Z-Axis angular rate sensors (gyroscopes) with a user-programmable full-scale range of ±250, ±500, ±1000, and ±2000°/sec and integrated 16-bit ADCs
  • Digitally-programmable low-pass filter
  • Gyroscope operating current: 3.2mA
  • Sleep mode current: 8μA

Accelerometer Features
The triple-axis MEMS accelerometer in MPU-9250 includes a wide range of features:

  • Digital-output triple-axis accelerometer with a programmable full scale range of ±2g, ±4g, ±8g and ±16g and integrated 16-bit ADCs
  • Accelerometer normal operating current: 450μA
  • Low power accelerometer mode current: 8.4μA at 0.98Hz, 19.8μA at 31.25Hz
  • Sleep mode current: 8μA
  • User-programmable interrupts
  • Wake-on-motion interrupt for low power operation of applications processor

Magnetometer Features
The triple-axis MEMS magnetometer in MPU-9250 includes a wide range of features:

  • 3-axis silicon monolithic Hall-effect magnetic sensor with magnetic concentrator
  • Wide dynamic measurement range and high resolution with lower current consumption.
  • Output data resolution of 14 bit (0.6μT/LSB) or 16 bit (15μT/LSB)
  • Full scale measurement range is ±4800μT
  • Magnetometer normal operating current: 280μA at 8Hz repetition rate
  • Self-test function with internal magnetic source to confirm magnetic sensor operation on end products

Additional Features
The MPU-9250 includes the following additional features:

  • Auxiliary master I2C bus for reading data from external sensors (e.g. pressure sensor)
  • 3.5mA operating current when all 9 motion sensing axes and the DMP are enabled
  • VDD supply voltage range of 2.43.6V
  • VDDIO reference voltage for auxiliary I2C devices
  • Smallest and thinnest QFN package for portable devices: 3x3x1mm
  • Minimal cross-axis sensitivity between the accelerometer, gyroscope and magnetometer axes
  • 512 byte FIFO buffer enables the applications processor to read the data in bursts
  • Digital-output temperature sensor
  • User-programmable digital filters for gyroscope, accelerometer, and temp sensor
  • 10,000 g shock tolerant
  • 400kHz Fast Mode I2C for communicating with all registers
  • 1MHz SPI serial interface for communicating with all registers
  • 20MHz SPI serial interface for reading sensor and interrupt registers

Code

You can roll your own code but I chose a library in the Arduino library manager called the MPU9250_asukiaaa

This is one of the default code examples

#include <MPU9250_asukiaaa.h>
 
#ifdef _ESP32_HAL_I2C_H_
#define SDA_PIN 21
#define SCL_PIN 22
#endif
 
MPU9250_asukiaaa mySensor;
float aX, aY, aZ, aSqrt, gX, gY, gZ, mDirection, mX, mY, mZ;
 
void setup() {
  Serial.begin(115200);
  while(!Serial);
  Serial.println("started");
 
#ifdef _ESP32_HAL_I2C_H_ // For ESP32
  Wire.begin(SDA_PIN, SCL_PIN);
  mySensor.setWire(&Wire);
#endif
 
  mySensor.beginAccel();
  mySensor.beginGyro();
  mySensor.beginMag();
 
  // You can set your own offset for mag values
  // mySensor.magXOffset = -50;
  // mySensor.magYOffset = -55;
  // mySensor.magZOffset = -10;
}
 
void loop() {
  uint8_t sensorId;
  if (mySensor.readId(&sensorId) == 0) {
    Serial.println("sensorId: " + String(sensorId));
  } else {
    Serial.println("Cannot read sensorId");
  }
 
  if (mySensor.accelUpdate() == 0) {
    aX = mySensor.accelX();
    aY = mySensor.accelY();
    aZ = mySensor.accelZ();
    aSqrt = mySensor.accelSqrt();
    Serial.println("accelX: " + String(aX));
    Serial.println("accelY: " + String(aY));
    Serial.println("accelZ: " + String(aZ));
    Serial.println("accelSqrt: " + String(aSqrt));
  } else {
    Serial.println("Cannod read accel values");
  }
 
  if (mySensor.gyroUpdate() == 0) {
    gX = mySensor.gyroX();
    gY = mySensor.gyroY();
    gZ = mySensor.gyroZ();
    Serial.println("gyroX: " + String(gX));
    Serial.println("gyroY: " + String(gY));
    Serial.println("gyroZ: " + String(gZ));
  } else {
    Serial.println("Cannot read gyro values");
  }
 
  if (mySensor.magUpdate() == 0) {
    mX = mySensor.magX();
    mY = mySensor.magY();
    mZ = mySensor.magZ();
    mDirection = mySensor.magHorizDirection();
    Serial.println("magX: " + String(mX));
    Serial.println("maxY: " + String(mY));
    Serial.println("magZ: " + String(mZ));
    Serial.println("horizontal direction: " + String(mDirection));
  } else {
    Serial.println("Cannot read mag values");
  }
 
  Serial.println("at " + String(millis()) + "ms");
  Serial.println(""); // Add an empty line
  delay(500);
}

Output

Here is an example of my output

sensorId: 113
accelX: -0.06
accelY: -0.08
accelZ: 1.04
accelSqrt: 1.04
gyroX: 0.67
gyroY: -0.49
gyroZ: -0.55
magX: 95.13
maxY: 8.12
magZ: -105.38
horizontal direction: 85.12
at 102570ms

Links

https://www.invensense.com/products/motion-tracking/9-axis/mpu-9250/

https://www.invensense.com/download-pdf/mpu-9250-datasheet/

 

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