IMU: MPU-6050

Working Principle

The InvenSense MPU-6050 is a 6-axis inertial measurement unit combining a 3-axis MEMS accelerometer and a 3-axis MEMS gyroscope on one chip. The accelerometer measures linear acceleration (including gravity), while the gyroscope measures angular velocity. Together they provide complete motion sensing.

Analogy: The accelerometer is like a marble-on-a-plate that slides when tilted. The gyroscope is like a spinning top that resists changes in orientation. Combining both gives you a full picture of how an object moves and rotates.

Electrical Characteristics

Parameter	Value
Supply Voltage	2.375 V – 3.46 V
Accelerometer Range	±2g, ±4g, ±8g, ±16g
Gyroscope Range	±250, ±500, ±1000, ±2000 °/s
ADC Resolution	16-bit
Interface	I2C (400 kHz) at 0x68/0x69
On-chip DMP	Digital Motion Processor for sensor fusion

Interfacing

Calibration

• Accelerometer offset: Place sensor flat; X and Y should read 0 g, Z should read +1 g. Record offsets.
• Gyroscope offset: Keep sensor stationary for 5 seconds; average readings are the zero-rate offset.
• Complementary filter: Combine accelerometer (stable, noisy) with gyroscope (smooth, drifts) using α = 0.98 to get drift-free tilt angles.

Code Example

/*
 * MPU-6050 Tilt Angle via Complementary Filter — Arduino
 * Requires: Wire.h (built-in)
 * Wiring: I2C — SCL→A5, SDA→A4, VCC→3.3V
 */
#include <Wire.h>

#define MPU_ADDR 0x68

float accelAngleX, gyroAngleX, compAngleX;
unsigned long prevTime;

void setup() {
    Serial.begin(115200);
    Wire.begin();

    /* Wake up MPU-6050 */
    Wire.beginTransmission(MPU_ADDR);
    Wire.write(0x6B);  /* PWR_MGMT_1 register */
    Wire.write(0x00);  /* Wake up (clear sleep bit) */
    Wire.endTransmission(true);

    prevTime = millis();
    compAngleX = 0;
}

void loop() {
    int16_t ax, ay, az, gx;

    /* Read accelerometer (0x3B-0x40) and gyro X (0x43-0x44) */
    Wire.beginTransmission(MPU_ADDR);
    Wire.write(0x3B);
    Wire.endTransmission(false);
    Wire.requestFrom(MPU_ADDR, 8, true);

    ax = Wire.read() << 8 | Wire.read();
    ay = Wire.read() << 8 | Wire.read();
    az = Wire.read() << 8 | Wire.read();
    /* Skip temp (2 bytes) — read gyro X */
    Wire.read(); Wire.read();

    Wire.beginTransmission(MPU_ADDR);
    Wire.write(0x43);
    Wire.endTransmission(false);
    Wire.requestFrom(MPU_ADDR, 2, true);
    gx = Wire.read() << 8 | Wire.read();

    /* Convert to physical units */
    float accelX = atan2(ay, az) * 180.0 / PI;
    float gyroRateX = gx / 131.0;  /* ±250°/s range */

    /* Complementary filter */
    unsigned long now = millis();
    float dt = (now - prevTime) / 1000.0;
    prevTime = now;

    compAngleX = 0.98 * (compAngleX + gyroRateX * dt) + 0.02 * accelX;

    Serial.print("Tilt X: ");
    Serial.print(compAngleX, 1);
    Serial.println("°");
    delay(10);
}

Real-World Applications

MPU-9250: 9-Axis with Magnetometer

The MPU-9250 integrates the MPU-6050’s 6-axis accelerometer/gyroscope with an AK8963 3-axis magnetometer, providing full 9-DoF orientation sensing in one package. The magnetometer adds absolute heading (compass), solving the MPU-6050’s yaw drift problem. Use a Madgwick or Mahony sensor fusion filter combining all 9 axes for drift-free 3D orientation.

ICM-20948: The Modern Successor

TDK InvenSense’s ICM-20948 is the recommended replacement for the discontinued MPU-9250. It offers 9-axis sensing (accel + gyro + AKM magnetometer) with lower noise, improved temperature stability, and an on-chip DMP (Digital Motion Processor) that outputs quaternions directly. It supports both I²C and SPI interfaces.

IMU Family Comparison

Feature	MPU-6050	MPU-9250	ICM-20948	BNO055
Axes	6 (A+G)	9 (A+G+M)	9 (A+G+M)	9 (A+G+M)
Magnetometer	✗	✓ (AK8963)	✓ (AK09916)	✓ (BMM150)
On-Chip Fusion	DMP (basic)	DMP (basic)	DMP (quaternion)	Full AHRS (quaternion, Euler, gravity)
Interface	I²C/SPI	I²C/SPI	I²C/SPI	I²C
Gyro Noise	0.005 °/s/√Hz	0.01 °/s/√Hz	0.015 °/s/√Hz	0.014 °/s/√Hz
Status	Active	Discontinued	Active	Active
Best For	Basic tilt	Legacy 9-axis	New 9-axis projects	Plug-and-play AHRS

Limitations

• Gyro drift: Without magnetometer correction, yaw angle drifts continuously. Use MPU-9250, ICM-20948, or BNO055 for drift-free heading.
• Vibration sensitivity: Engine vibration corrupts accelerometer data; apply low-pass filtering.
• No absolute heading: The MPU-6050 alone has no compass; pair with HMC5883L or upgrade to a 9-axis IMU.
• MPU-9250 discontinued: InvenSense no longer manufactures the MPU-9250; use ICM-20948 for new designs.