How to Use MPU9250/GY -91: Examples, Pinouts, and Specs

The MPU9250/GY-91 is a multi-faceted motion tracking device that integrates a 3-axis gyroscope, a 3-axis accelerometer, and a 3-axis compass. This 9-axis sensor is widely used in the field of robotics, wearable devices, and motion-based game controllers, providing precise data for orientation and motion sensing.

• Inertial Measurement Units (IMUs) for robotics
• Orientation tracking for virtual reality (VR) devices
• Motion analysis in sports technology
• Drone stabilization and navigation
• Smartphone and tablet motion features

• Voltage: 2.4V - 3.6V
• Current: 10μA in low-power accelerometer only mode
• Gyroscope Range: ±250, ±500, ±1000, ±2000°/sec
• Accelerometer Range: ±2g, ±4g, ±8g, ±16g
• Magnetometer Range (Compass): ±4800μT
• Communication: I2C/SPI

1. Powering the Device: Connect the VCC pin to a 2.4V - 3.6V power source and the GND pin to the ground.
2. Communication Setup: For I2C communication, connect SCL to the I2C clock and SDA to the I2C data. For SPI, connect SCLK, SDI, SDO, and NCS accordingly.
3. Address Selection: The AD0/SDO pin can be used to set the I2C address. Connect it to VCC or GND to select between the two available addresses.
4. Interrupts (Optional): The INT pin can be connected to an external interrupt on a microcontroller to trigger actions when data is ready or other events occur.

• Ensure that the power supply is within the specified voltage range to prevent damage.
• Use pull-up resistors on the I2C lines if they are not built into the microcontroller.
• For SPI communication, ensure that the NCS pin is kept high when the device is not in use.
• When using the interrupt feature, configure the MPU9250/GY-91 registers to set up the interrupt conditions.

#include <Wire.h>

// MPU9250 I2C address (depends on AD0 pin, check datasheet)
const int MPU9250_ADDRESS = 0x68;

void setup() {
  Wire.begin(); // Initialize I2C
  Serial.begin(9600); // Start serial communication at 9600 baud
  setupMPU9250(); // Setup MPU9250 registers for operation
}

void loop() {
  // Read sensor data and print it
  readSensorData();
  delay(100); // Delay for readability
}

void setupMPU9250() {
  // Write to the power management register to wake up the MPU9250
  writeMPU9250Register(MPU9250_ADDRESS, 0x6B, 0x00);
}

void writeMPU9250Register(byte address, byte reg, byte data) {
  Wire.beginTransmission(address);
  Wire.write(reg);
  Wire.write(data);
  Wire.endTransmission();
}

void readSensorData() {
  Wire.beginTransmission(MPU9250_ADDRESS);
  Wire.write(0x3B); // Starting register for accelerometer data
  Wire.endTransmission(false);
  Wire.requestFrom(MPU9250_ADDRESS, 14, true); // Request 14 bytes from the MPU9250

  // Read and process accelerometer, gyroscope, and temperature data
  // Accelerometer data
  int16_t ax = Wire.read() << 8 | Wire.read();
  int16_t ay = Wire.read() << 8 | Wire.read();
  int16_t az = Wire.read() << 8 | Wire.read();
  // Temperature data (not used in this example)
  Wire.read(); Wire.read();
  // Gyroscope data
  int16_t gx = Wire.read() << 8 | Wire.read();
  int16_t gy = Wire.read() << 8 | Wire.read();
  int16_t gz = Wire.read() << 8 | Wire.read();

  // Print the sensor data
  Serial.print("Accel: ");
  Serial.print("X="); Serial.print(ax);
  Serial.print(" Y="); Serial.print(ay);
  Serial.print(" Z="); Serial.println(az);
  Serial.print("Gyro: ");
  Serial.print("X="); Serial.print(gx);
  Serial.print(" Y="); Serial.print(gy);
  Serial.print(" Z="); Serial.println(gz);
}

• No Data Output: Ensure that the device is properly powered and that the I2C/SPI connections are correct.
• Inaccurate Readings: Calibrate the sensor for your specific application environment.
• Intermittent Connection: Check for loose connections and ensure that the pull-up resistors are in place for I2C.

• Power Supply Issues: Use a multimeter to verify the voltage at the VCC pin.
• Communication Errors: Use an I2C scanner sketch to check if the MPU9250 is detected on the bus.
• Sensor Calibration: Follow the manufacturer's guidelines for calibrating the gyroscope, accelerometer, and compass.

Q: Can the MPU9250/GY-91 be used with both 3.3V and 5V microcontrollers? A: Yes, but ensure that the voltage levels for communication are compatible or use level shifters if necessary.

Q: How can I change the I2C address of the MPU9250? A: The I2C address can be changed by connecting the AD0/SDO pin to either VCC or GND.

Q: What is the default I2C address of the MPU9250? A: The default I2C address is 0x68 when AD0/SDO is connected to GND. It changes to 0x69 when connected to VCC.

Q: How do I interpret the raw data from the MPU9250? A: The raw data needs to be converted using the sensitivity levels specified in the datasheet. This will give you the actual measurements in the appropriate units (e.g., g for acceleration, °/sec for gyroscope, μT for magnetometer).