MPU6050

Contributed by Shriyans.

The InvenSense MPU6050 is a high-performance 6-axis MotionTracking device that combines a 3-axis gyroscope and a 3-axis accelerometer on the same silicon die, communicating over an I2C serial bus.

The driver uses the uorb interface.

Application Programming Interface

#include <nuttx/sensors/mpu6050.h>

The MPU6050 registration function allows the driver to be registered as a uORB lower-half sensor driver. Registering this driver will cause two separate uORB topics to appear under /dev/uorb/:

sensor_accel<n> - Accelerometer topic reporting linear acceleration in m/s² and temperature.
sensor_gyro<n> - Gyroscope topic reporting angular velocity in rad/s and temperature.

Where n is the device number passed during device registration (e.g., 0).

/* Example uORB sensor registration on I2C bus 0 at default address 0x68 */

int err = mpu6050_register(0, i2c_master, MPU6050_ADDR_LOW, NULL);
if (err < 0)
  {
    syslog(LOG_ERR, "Failed to register MPU6050: %d\n", err);
  }

The device samples at 100 Hz.

Acquisition Modes

The driver reads the device on demand by default: a sample is taken when the application reads the topic, and is timestamped at that moment.

With CONFIG_SENSORS_MPU6050_INT the device drives the acquisition instead, through its data ready interrupt. Samples are then timestamped when they were measured rather than when they were asked for, and both topics are published from a single read, so accelerometer and gyroscope share one timestamp. This requires the INT pin to be wired, and the board to pass a struct mpu6050_config_s whose attach member connects that pin to the driver:

static int board_mpu6050_attach(FAR const struct mpu6050_config_s *config,
                                xcpt_t isr, FAR void *arg)
{
  /* Configure the GPIO for a rising edge and attach isr to it */
}

static const struct mpu6050_config_s g_mpu6050_config =
{
  .attach = board_mpu6050_attach,
};

int err = mpu6050_register(0, i2c_master, MPU6050_ADDR_LOW,
                           &g_mpu6050_config);

Registration fails with -EINVAL if the option is enabled and no attach is supplied, since the interrupt is the only source of samples in that build.

Configuration Options

CONFIG_SENSORS_MPU6050 - Enables uORB driver support for the InvenSense MPU6050 6-axis MotionTracker over I2C.
CONFIG_SENSORS_MPU6050_INT - Takes samples from the data ready interrupt instead of reading the device on demand. Requires board support, see Acquisition Modes.

Supported Operations

The MPU6050 uORB driver supports standard sensor operations (activate, set_interval, batch, and control), plus fetch when reading on demand. An instance provides either fetch or interrupt driven delivery, never both. It acquires simultaneous 3-axis accelerometer and 3-axis gyroscope samples, applies appropriate scale conversions, and publishes them to their respective uORB topics.

Example Usage (uorb_listener)

Once registered on target hardware, the MPU6050 topics can be verified directly from the NuttX shell (NSH) using the uorb_listener utility:

nsh> uorb_listener sensor_accel0 5
TOPIC: sensor_accel0 #0
timestamp: 12345678
x: 0.0210
y: 0.0035
z: 9.8066
temperature: 25.4000

nsh> uorb_listener sensor_gyro0 5
TOPIC: sensor_gyro0 #0
timestamp: 12345680
x: 0.0012
y: -0.0004
z: 0.0001
temperature: 25.4000