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FastIMU

1

Supported IMUS:

  • MPU9255
  • MPU9250
  • MPU6886
  • MPU6515
  • MPU6500
  • MPU6050
  • ICM20689
  • ICM20690
  • ICM20948
  • BMI055
  • BMX055 (Magnetometer currently untested)
  • BMI160
  • LSM6DS3 (And some of it's variants)
  • LSM6DSL (currently untested)
  • QMI8658

Supported Magnetometers:

  • QMC5883L
  • HMC5883L
  • AK8975
  • AK8963
  • AK09918
  • BMM150

Using non default I2C ports:

If you're planning on using an IMU on a non-default I2C port, you can specify the port in the constructor of your IMU, for example:

ICM20689 IMU1(Wire); 
MPU6500 IMU2(Wire1);

creates two IMU objects, ICM20689 will be using the I2C port assigned to Wire and MPU6500 will be on the I2C port assigned to Wire1.

Hybrid IMU's:

You can also use Hybrid IMU's, which means you can add any supported magnetometer to any supported IMU by using the IMU_HYBRID class as follows:

IMU_HYBRID<IMU, MAG> IMU(Wire);

For example

IMU_HYBRID<MPU6050, QMC5883L> IMU(Wire);

creates a hybrid MPU6050 and QMC5883L IMU object that behaves as a single IMU, that returns accel and gyro values from the MPU6050 and magnetometer values from the QMC5883L respectively

Planned:

  • BNO080 (probably soonish)
  • GY-85
  • BNO055 (the one I bought is DOA... might take a bit)
  • BMI270 (if I can get my hands on one)

Data types

  • AccelData Contains all three axis of Accelerometer data, these are named accelX, accelY and accelZ. Also contains a timestamp field (uint32_t, microseconds from micros()) updated only when the sensor has new data.

  • GyroData Contains all three axis of Gyroscope data, these are named gyroX, gyroY and gyroZ. Also contains a timestamp field updated independently of AccelData.

  • MagData Contains all three axis of Magnetometer data, these are named magX, magY and magZ. Also contains a timestamp field updated only when the magnetometer has new data.

  • Quaternion Contains Quaternion data, the components are named qW, qX, qY and qZ. Also contains a timestamp field.

  • CalData Contains a boolean component named valid that must be set to true if the data is valid, it contains float array named accelBias for accelerometer biases, one named gyroBias for gyroscope bias, one named magBias for magnetometer biases and one named magScale for magnetometer scaling.

Functions

  • init Takes in a calData function and an optional byte address, this function initializes the IMU, it defaults to the maximum ranges allowed by the IMU. This function will return a 0 if initialization was successful and a negative number if it failed to connect to the IMU. if no address is provided, the default for the selected IMU will be used.

  • update Reads new IMU data if available.

  • getAccel Takes in a pointer to AccelData and copies new accelerometer data to it, should be called after update.

  • getGyro Takes in a pointer to GyroData and copies new gyroscope data to it, should be called after update.

  • getMag Takes in a pointer to MagData and copies new magnetometer data to it, should be called after update. Will only return new magnetometer data if the IMU has a magnetometer.

  • getQuat Takes in a pointer to a Quaternion and copies new quaternion data to it, should be called after update. Will only return new Quaternion data if the IMU has a Quaternion output.

  • getTemp Returns temperature float data in °C, should be called after update, isn't very accurate.

  • setGyroRange Takes in an integer with the dps range wanted, (for example 2000 for ±2000dps), returns 0 if successful, returns -1 if the input range is not valid.

  • setAccelRange Takes in an integer with the dps range wanted, (for example 8 for ±8g), returns 0 if successful, returns -1 if the input range is not valid.

  • setIMUGeometry Takes in an integer with the wanted geometry index, rotates IMU measurements to match vr headset IMU mount. (see chart below).

  • setAccelODR Takes in an integer target output data rate in Hz and sets the accelerometer ODR to the nearest supported rate greater than or equal to the requested value. Returns the actual ODR that was set, or -1 if the sensor does not support configurable ODR.

  • setGyroODR Same as setAccelODR but for the gyroscope. On some sensors (e.g. MPU6050-family) accel and gyro share a rate divider so setting one affects both.

  • setMagODR Same as setAccelODR but for the magnetometer. Returns -1 if the IMU has no magnetometer or if it does not support a configurable continuous ODR (e.g. AK8975).

  • getAccelODR Returns the current accelerometer ODR in Hz as last set by setAccelODR, or -1 if not supported.

  • getGyroODR Returns the current gyroscope ODR in Hz as last set by setGyroODR, or -1 if not supported.

  • getMagODR Returns the current magnetometer ODR in Hz as last set by setMagODR, or -1 if not supported.

  • setAccelLPF Takes in an integer target low-pass filter cutoff frequency in Hz and sets the accelerometer LPF to the nearest available value. Returns the actual cutoff frequency that was set, 0 if the filter was disabled, or -1 if the sensor does not support a configurable accelerometer LPF (e.g. MPU6050, BMI055/BMX055 accel). Passing 0 disables the filter or sets the widest available bandwidth on sensors where bypass is not possible.

  • setGyroLPF Same as setAccelLPF but for the gyroscope. On sensors where the available bandwidths are ODR-dependent (e.g. LSM6DS3/DSL, QMI8658, BMI160, BMI055/BMX055), the nearest available bandwidth at the current ODR is selected without changing the ODR.

  • getAccelLPF Returns the accelerometer LPF cutoff frequency in Hz as last set by setAccelLPF, 0 if disabled, or -1 if not supported.

  • getGyroLPF Returns the gyroscope LPF cutoff frequency in Hz as last set by setGyroLPF, 0 if disabled, or -1 if not supported.

  • calibrateAccelGyro Takes in a pointer to calibration data and runs a Accelerometer and Gyroscope calibration, storing the new accelerometer and gyroscope calibration data in it. the IMU should be kept completely still and level during this.

  • calibrateMag Takes in a pointer to Calibration data and runs a Accelerometer and Gyroscope calibration, storing the new accelerometer and gyroscope calibration data in it. the IMU should be moved in a figure eight pattern while calibrating, calibration takes around 15 seconds.

  • hasMagnetometer Returns true if the IMU has a magnetometer.

  • hasTemperature Returns true if the IMU has a thermometer.

  • hasQuatOutput Returns true if the IMU has a direct quaternion output.

  • IMUName Returns a string containing the IMU's name.

  • IMUType Returns a string containing the IMU's type.

  • IMUManufacturer Returns a string containing the IMU's manufacturer.

Supported IMU VR geometries (and their index numbers):

2

TODO: VQF? built in filters?
TODO: get DMP working for pure quaternion output from invsense IMU's
TODO: get FIFO working for all IMU's that have it.
TODO: get proper matrix magnetometer calibration working instead of the current scalar garbage.