C/C++ - IMU Brick 2.0

Note

This Brick is currently in the prototype stage and the software/hardware as well as the documentation is in an incomplete state.

This is the description of the C/C++ API bindings for the IMU Brick 2.0. General information and technical specifications for the IMU Brick 2.0 are summarized in its hardware description.

An installation guide for the C/C++ API bindings is part of their general description.

Examples

The example code below is Public Domain (CC0 1.0).

API

Every function of the C/C++ bindings returns an integer which describes an error code. Data returned from the device, when a getter is called, is handled via call by reference. These parameters are labeled with the ret_ prefix.

Possible error codes are:

  • E_OK = 0
  • E_TIMEOUT = -1
  • E_NO_STREAM_SOCKET = -2
  • E_HOSTNAME_INVALID = -3
  • E_NO_CONNECT = -4
  • E_NO_THREAD = -5
  • E_NOT_ADDED = -6 (unused since bindings version 2.0.0)
  • E_ALREADY_CONNECTED = -7
  • E_NOT_CONNECTED = -8
  • E_INVALID_PARAMETER = -9
  • E_NOT_SUPPORTED = -10
  • E_UNKNOWN_ERROR_CODE = -11

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void imu_v2_create(IMUV2 *imu_v2, const char *uid, IPConnection *ipcon)

Creates the device object imu_v2 with the unique device ID uid and adds it to the IPConnection ipcon:

IMUV2 imu_v2;
imu_v2_create(&imu_v2, "YOUR_DEVICE_UID", &ipcon);

This device object can be used after the IP connection has been connected (see examples above).

void imu_v2_destroy(IMUV2 *imu_v2)

Removes the device object imu_v2 from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int imu_v2_get_all_data(IMUV2 *imu_v2, int16_t ret_acceleration[3], int16_t ret_magnetic_field[3], int16_t ret_angular_velocity[3], int16_t ret_euler_angle[3], int16_t ret_quaternion[4], int16_t ret_linear_acceleration[3], int16_t ret_gravity_vector[3], int8_t *ret_temperature, uint8_t *ret_calibration_status)

Return all of the available data of the IMU Brick.

The calibration status consists of four pairs of two bits. Each pair of bits represents the status of the current calibration.

  • bit 0-1: Magnetometer
  • bit 2-3: Accelerometer
  • bit 4-5: Gyroscope
  • bit 6-7: System

A value of 0 means for "not calibrated" and a value of 3 means "fully calibrated". In your program you should always be able to ignore the calibration status, it is used by the calibration window of the Brick Viewer and it can be ignored after the first calibration. See the documentation in the calibration window for more information regarding the calibration of the IMU Brick.

If you want to get the data periodically, it is recommended to use the callback IMU_V2_CALLBACK_ALL_DATA and set the period with imu_v2_set_all_data_period().

int imu_v2_leds_on(IMUV2 *imu_v2)

Turns the orientation and direction LEDs of the IMU Brick on.

int imu_v2_leds_off(IMUV2 *imu_v2)

Turns the orientation and direction LEDs of the IMU Brick off.

int imu_v2_are_leds_on(IMUV2 *imu_v2, bool *ret_leds)

Returns true if the orientation and direction LEDs of the IMU Brick are on, false otherwise.

Advanced Functions

int imu_v2_get_acceleration(IMUV2 *imu_v2, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)

Returns the calibrated acceleration from the accelerometer for the x, y and z axis in 1/100 m/s².

If you want to get the acceleration periodically, it is recommended to use the callback IMU_V2_CALLBACK_ACCELERATION and set the period with imu_v2_set_acceleration_period().

int imu_v2_get_magnetic_field(IMUV2 *imu_v2, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)

Returns the calibrated magnetic field from the magnetometer for the x, y and z axis in 1/16 µT (Microtesla).

If you want to get the magnetic field periodically, it is recommended to use the callback IMU_V2_CALLBACK_MAGNETIC_FIELD and set the period with imu_v2_set_magnetic_field_period().

int imu_v2_get_angular_velocity(IMUV2 *imu_v2, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)

Returns the calibrated angular velocity from the gyroscope for the x, y and z axis in 1/16 °/s.

If you want to get the angular velocity periodically, it is recommended to use the callback IMU_V2_CALLBACK_ANGULAR_VELOCITY and set the period with imu_v2_set_angular_velocity_period().

int imu_v2_get_temperature(IMUV2 *imu_v2, int8_t *ret_temperature)

Returns the temperature of the IMU Brick. The temperature is given in °C. The temperature is measured in the core of the BNO055 IC, it is not the ambient temperature

int imu_v2_get_orientation(IMUV2 *imu_v2, int16_t *ret_heading, int16_t *ret_roll, int16_t *ret_pitch)

Returns the current orientation (heading, roll, pitch) of the IMU Brick as Euler angles in 1/16 degree. Note that Euler angles always experience a gimbal lock.

We recommend that you use quaternions instead.

The rotation angle has the following ranges:

  • heading: 0° to 360°
  • roll: -90° to +90°
  • pitch: -180° to +180°

If you want to get the orientation periodically, it is recommended to use the callback IMU_V2_CALLBACK_ORIENTATION and set the period with imu_v2_set_orientation_period().

int imu_v2_get_linear_acceleration(IMUV2 *imu_v2, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)

Returns the linear acceleration of the IMU Brick for the x, y and z axis in 1/100 m/s².

The linear acceleration is the acceleration in each of the three axis of the IMU Brick with the influences of gravity removed.

It is also possible to get the gravity vector with the influence of linear acceleration removed, see imu_v2_get_gravity_vector().

If you want to get the linear acceleration periodically, it is recommended to use the callback IMU_V2_CALLBACK_LINEAR_ACCELERATION and set the period with imu_v2_set_linear_acceleration_period().

int imu_v2_get_gravity_vector(IMUV2 *imu_v2, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)

Returns the current gravity vector of the IMU Brick for the x, y and z axis in 1/100 m/s².

The gravity vector is the acceleration that occurs due to gravity. Influences of additional linear acceleration are removed.

It is also possible to get the linear acceleration with the influence of gravity removed, see imu_v2_get_linear_acceleration().

If you want to get the gravity vector periodically, it is recommended to use the callback IMU_V2_CALLBACK_GRAVITY_VECTOR and set the period with imu_v2_set_gravity_vector_period().

int imu_v2_get_quaternion(IMUV2 *imu_v2, int16_t *ret_w, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)

Returns the current orientation (w, x, y, z) of the IMU Brick as quaternions.

You have to divide the returns values by 16383 (14 bit) to get the usual range of -1.0 to +1.0 for quaternions.

If you want to get the quaternions periodically, it is recommended to use the callback IMU_V2_CALLBACK_QUATERNION and set the period with imu_v2_set_quaternion_period().

int imu_v2_save_calibration(IMUV2 *imu_v2, bool *ret_calibration_done)

A call of this function saves the current calibration to be used as a starting point for the next restart of continuous calibration of the IMU Brick.

A return value of true means that the calibration could be used and false means that it could not be used (this happens if the calibration status is not "fully calibrated").

This function is used by the calibration window of the Brick Viewer, you should not need to call it in your program.

int imu_v2_get_api_version(IMUV2 *imu_v2, uint8_t ret_api_version[3])

Returns the version of the API definition (major, minor, revision) implemented by this API bindings. This is neither the release version of this API bindings nor does it tell you anything about the represented Brick or Bricklet.

int imu_v2_get_response_expected(IMUV2 *imu_v2, uint8_t function_id, bool *ret_response_expected)

Returns the response expected flag for the function specified by the function ID parameter. It is true if the function is expected to send a response, false otherwise.

For getter functions this is enabled by default and cannot be disabled, because those functions will always send a response. For callback configuration functions it is enabled by default too, but can be disabled by imu_v2_set_response_expected(). For setter functions it is disabled by default and can be enabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

See imu_v2_set_response_expected() for the list of function ID defines available for this function.

int imu_v2_set_response_expected(IMUV2 *imu_v2, uint8_t function_id, bool response_expected)

Changes the response expected flag of the function specified by the function ID parameter. This flag can only be changed for setter (default value: false) and callback configuration functions (default value: true). For getter functions it is always enabled and callbacks it is always disabled.

Enabling the response expected flag for a setter function allows to detect timeouts and other error conditions calls of this setter as well. The device will then send a response for this purpose. If this flag is disabled for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

The following function ID defines are available for this function:

  • IMU_V2_FUNCTION_LEDS_ON = 10
  • IMU_V2_FUNCTION_LEDS_OFF = 11
  • IMU_V2_FUNCTION_SET_ACCELERATION_PERIOD = 14
  • IMU_V2_FUNCTION_SET_MAGNETIC_FIELD_PERIOD = 16
  • IMU_V2_FUNCTION_SET_ANGULAR_VELOCITY_PERIOD = 18
  • IMU_V2_FUNCTION_SET_TEMPERATURE_PERIOD = 20
  • IMU_V2_FUNCTION_SET_ORIENTATION_PERIOD = 22
  • IMU_V2_FUNCTION_SET_LINEAR_ACCELERATION_PERIOD = 24
  • IMU_V2_FUNCTION_SET_GRAVITY_VECTOR_PERIOD = 26
  • IMU_V2_FUNCTION_SET_QUATERNION_PERIOD = 28
  • IMU_V2_FUNCTION_SET_ALL_DATA_PERIOD = 30
  • IMU_V2_FUNCTION_ENABLE_STATUS_LED = 238
  • IMU_V2_FUNCTION_DISABLE_STATUS_LED = 239
  • IMU_V2_FUNCTION_RESET = 243
int imu_v2_set_response_expected_all(IMUV2 *imu_v2, bool response_expected)

Changes the response expected flag for all setter and callback configuration functions of this device at once.

int imu_v2_enable_status_led(IMUV2 *imu_v2)

Enables the status LED.

The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.

The default state is enabled.

int imu_v2_disable_status_led(IMUV2 *imu_v2)

Disables the status LED.

The status LED is the blue LED next to the USB connector. If enabled is is on and it flickers if data is transfered. If disabled it is always off.

The default state is enabled.

int imu_v2_is_status_led_enabled(IMUV2 *imu_v2, bool *ret_enabled)

Returns true if the status LED is enabled, false otherwise.

int imu_v2_get_protocol1_bricklet_name(IMUV2 *imu_v2, char port, uint8_t *ret_protocol_version, uint8_t ret_firmware_version[3], char ret_name[40])

Returns the firmware and protocol version and the name of the Bricklet for a given port.

This functions sole purpose is to allow automatic flashing of v1.x.y Bricklet plugins.

int imu_v2_get_chip_temperature(IMUV2 *imu_v2, int16_t *ret_temperature)

Returns the temperature in °C/10 as measured inside the microcontroller. The value returned is not the ambient temperature!

The temperature is only proportional to the real temperature and it has an accuracy of +-15%. Practically it is only useful as an indicator for temperature changes.

int imu_v2_reset(IMUV2 *imu_v2)

Calling this function will reset the Brick. Calling this function on a Brick inside of a stack will reset the whole stack.

After a reset you have to create new device objects, calling functions on the existing ones will result in undefined behavior!

int imu_v2_get_identity(IMUV2 *imu_v2, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)

Returns the UID, the UID where the Brick is connected to, the position, the hardware and firmware version as well as the device identifier.

The position can be '0'-'8' (stack position).

The device identifier numbers can be found here. There is also a constant for the device identifier of this Brick.

Callback Configuration Functions

void imu_v2_register_callback(IMUV2 *imu_v2, uint8_t id, void *callback, void *user_data)

Registers a callback with ID id to the function callback. The user_data will be given as a parameter of the callback.

The available IDs with corresponding function signatures are listed below.

int imu_v2_set_acceleration_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_ACCELERATION callback is triggered periodically. A value of 0 turns the callback off.

The default value is 0.

int imu_v2_get_acceleration_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_acceleration_period().

int imu_v2_set_magnetic_field_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_MAGNETIC_FIELD callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_magnetic_field_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_magnetic_field_period().

int imu_v2_set_angular_velocity_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_ANGULAR_VELOCITY callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_angular_velocity_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_angular_velocity_period().

int imu_v2_set_temperature_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_TEMPERATURE callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_temperature_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_temperature_period().

int imu_v2_set_orientation_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_ORIENTATION callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_orientation_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_orientation_period().

int imu_v2_set_linear_acceleration_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_LINEAR_ACCELERATION callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_linear_acceleration_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_linear_acceleration_period().

int imu_v2_set_gravity_vector_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_GRAVITY_VECTOR callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_gravity_vector_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_gravity_vector_period().

int imu_v2_set_quaternion_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_QUATERNION callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_quaternion_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_quaternion_period().

int imu_v2_set_all_data_period(IMUV2 *imu_v2, uint32_t period)

Sets the period in ms with which the IMU_V2_CALLBACK_ALL_DATA callback is triggered periodically. A value of 0 turns the callback off.

int imu_v2_get_all_data_period(IMUV2 *imu_v2, uint32_t *ret_period)

Returns the period as set by imu_v2_set_all_data_period().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the imu_v2_register_callback() function. The parameters consist of the device object, the callback ID, the callback function and optional user data:

void my_callback(int p, void *user_data) {
    printf("parameter: %d\n", p);
}

imu_v2_register_callback(&imu_v2, IMU_V2_CALLBACK_EXAMPLE, (void *)my_callback, NULL);

The available constants with corresponding callback function signatures are described below.

Note

Using callbacks for recurring events is always preferred compared to using getters. It will use less USB bandwidth and the latency will be a lot better, since there is no round trip time.

IMU_V2_CALLBACK_ACCELERATION
void callback(int16_t x, int16_t y, int16_t z, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_acceleration_period(). The parameters are the acceleration for the x, y and z axis.

IMU_V2_CALLBACK_MAGNETIC_FIELD
void callback(int16_t x, int16_t y, int16_t z, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_magnetic_field_period(). The parameters are the magnetic field for the x, y and z axis.

IMU_V2_CALLBACK_ANGULAR_VELOCITY
void callback(int16_t x, int16_t y, int16_t z, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_angular_velocity_period(). The parameters are the angular velocity for the x, y and z axis.

IMU_V2_CALLBACK_TEMPERATURE
void callback(int8_t temperature, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_temperature_period(). The parameter is the temperature.

IMU_V2_CALLBACK_LINEAR_ACCELERATION
void callback(int16_t x, int16_t y, int16_t z, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_linear_acceleration_period(). The parameters are the linear acceleration for the x, y and z axis.

IMU_V2_CALLBACK_GRAVITY_VECTOR
void callback(int16_t x, int16_t y, int16_t z, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_gravity_vector_period(). The parameters gravity vector for the x, y and z axis.

IMU_V2_CALLBACK_ORIENTATION
void callback(int16_t heading, int16_t roll, int16_t pitch, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_orientation_period(). The parameters are the orientation (heading (yaw), roll, pitch) of the IMU Brick in Euler angles. See imu_v2_get_orientation() for details.

IMU_V2_CALLBACK_QUATERNION
void callback(int16_t w, int16_t x, int16_t y, int16_t z, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_quaternion_period(). The parameters are the orientation (x, y, z, w) of the IMU Brick in quaternions. See imu_v2_get_quaternion() for details.

IMU_V2_CALLBACK_ALL_DATA
void callback(int16_t acceleration[3], int16_t magnetic_field[3], int16_t angular_velocity[3], int16_t euler_angle[3], int16_t quaternion[4], int16_t linear_acceleration[3], int16_t gravity_vector[3], int8_t temperature, uint8_t calibration_status, void *user_data)

This callback is triggered periodically with the period that is set by imu_v2_set_all_data_period(). The parameters are as for imu_v2_get_all_data().

Constants

IMU_V2_DEVICE_IDENTIFIER

This constant is used to identify a IMU Brick 2.0.

The imu_v2_get_identity() function and the IPCON_CALLBACK_ENUMERATE callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

Creative Commons Licence The content of this page is licensed under Creative Commons Attribution 3.0 Unported License.