Software / API Bindings / C/C++ / API Reference and Examples / Bricks (Discontinued) / IMU Brick

C/C++ - IMU Brick¶

This is the description of the C/C++ API bindings for the IMU Brick. General information and technical specifications for the IMU Brick 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).

Simple¶

Download (example_simple.c)

#include <stdio.h>

#include "ip_connection.h"
#include "brick_imu.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XXYYZZ" // Change XXYYZZ to the UID of your IMU Brick

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    IMU imu;
    imu_create(&imu, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Get current quaternion
    float x, y, z, w;
    if(imu_get_quaternion(&imu, &x, &y, &z, &w) < 0) {
        fprintf(stderr, "Could not get quaternion, probably timeout\n");
        return 1;
    }

    printf("Quaternion [X]: %f\n", x);
    printf("Quaternion [Y]: %f\n", y);
    printf("Quaternion [Z]: %f\n", z);
    printf("Quaternion [W]: %f\n", w);

    printf("Press key to exit\n");
    getchar();
    imu_destroy(&imu);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

Callback¶

Download (example_callback.c)

#include <stdio.h>

#include "ip_connection.h"
#include "brick_imu.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XXYYZZ" // Change XXYYZZ to the UID of your IMU Brick

// Callback function for quaternion callback
void cb_quaternion(float x, float y, float z, float w, void *user_data) {
    (void)user_data; // avoid unused parameter warning

    printf("Quaternion [X]: %f\n", x);
    printf("Quaternion [Y]: %f\n", y);
    printf("Quaternion [Z]: %f\n", z);
    printf("Quaternion [W]: %f\n", w);
    printf("\n");
}

int main(void) {
    // Create IP connection
    IPConnection ipcon;
    ipcon_create(&ipcon);

    // Create device object
    IMU imu;
    imu_create(&imu, UID, &ipcon);

    // Connect to brickd
    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
        fprintf(stderr, "Could not connect\n");
        return 1;
    }
    // Don't use device before ipcon is connected

    // Register quaternion callback to function cb_quaternion
    imu_register_callback(&imu,
                          IMU_CALLBACK_QUATERNION,
                          (void (*)(void))cb_quaternion,
                          NULL);

    // Set period for quaternion callback to 1s (1000ms)
    imu_set_quaternion_period(&imu, 1000);

    printf("Press key to exit\n");
    getchar();
    imu_destroy(&imu);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

API¶

Most functions of the C/C++ bindings return an error code (e_code). Data returned from the device, when a getter is called, is handled via output parameters. 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 C/C++ 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
E_STREAM_OUT_OF_SYNC = -12
E_INVALID_UID = -13
E_NON_ASCII_CHAR_IN_SECRET = -14
E_WRONG_DEVICE_TYPE = -15
E_DEVICE_REPLACED = -16
E_WRONG_RESPONSE_LENGTH = -17

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions¶

void imu_create(IMU *imu, const char *uid, IPConnection *ipcon)¶

Parameters:	imu – Type: IMU * uid – Type: const char * ipcon – Type: IPConnection *

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

IMU imu;
imu_create(&imu, "YOUR_DEVICE_UID", &ipcon);

This device object can be used after the IP connection has been connected.

void imu_destroy(IMU *imu)¶

Parameters:	imu – Type: IMU *

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

int imu_get_orientation(IMU *imu, int16_t *ret_roll, int16_t *ret_pitch, int16_t *ret_yaw)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_roll – Type: int16_t, Unit: 1/100 °, Range: [-18000 to 18000] ret_pitch – Type: int16_t, Unit: 1/100 °, Range: [-18000 to 18000] ret_yaw – Type: int16_t, Unit: 1/100 °, Range: [-18000 to 18000]
Returns:	e_code – Type: int

Returns the current orientation (roll, pitch, yaw) of the IMU Brick as Euler angles. Note that Euler angles always experience a gimbal lock.

We recommend that you use quaternions instead.

The order to sequence in which the orientation values should be applied is roll, yaw, pitch.

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

int imu_get_quaternion(IMU *imu, float *ret_x, float *ret_y, float *ret_z, float *ret_w)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_x – Type: float, Range: [-1.0f to 1.0f] ret_y – Type: float, Range: [-1.0f to 1.0f] ret_z – Type: float, Range: [-1.0f to 1.0f] ret_w – Type: float, Range: [-1.0f to 1.0f]
Returns:	e_code – Type: int

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

You can go from quaternions to Euler angles with the following formula:

xAngle = atan2(2*y*w - 2*x*z, 1 - 2*y*y - 2*z*z)
yAngle = atan2(2*x*w - 2*y*z, 1 - 2*x*x - 2*z*z)
zAngle =  asin(2*x*y + 2*z*w)

This process is not reversible, because of the gimbal lock.

It is also possible to calculate independent angles. You can calculate yaw, pitch and roll in a right-handed vehicle coordinate system according to DIN70000 with:

yaw   =  atan2(2*x*y + 2*w*z, w*w + x*x - y*y - z*z)
pitch = -asin(2*w*y - 2*x*z)
roll  = -atan2(2*y*z + 2*w*x, -w*w + x*x + y*y - z*z))

Converting the quaternions to an OpenGL transformation matrix is possible with the following formula:

matrix = [[1 - 2*(y*y + z*z),     2*(x*y - w*z),     2*(x*z + w*y), 0],
          [    2*(x*y + w*z), 1 - 2*(x*x + z*z),     2*(y*z - w*x), 0],
          [    2*(x*z - w*y),     2*(y*z + w*x), 1 - 2*(x*x + y*y), 0],
          [                0,                 0,                 0, 1]]

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

int imu_leds_on(IMU *imu)¶

Parameters:	imu – Type: IMU *
Returns:	e_code – Type: int

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

int imu_leds_off(IMU *imu)¶

Parameters:	imu – Type: IMU *
Returns:	e_code – Type: int

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

int imu_are_leds_on(IMU *imu, bool *ret_leds)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_leds – Type: bool, Default: true
Returns:	e_code – Type: int

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

int imu_set_convergence_speed(IMU *imu, uint16_t speed)¶

Parameters:	imu – Type: IMU * speed – Type: uint16_t, Unit: 1 °/s, Range: [0 to 2¹⁶ - 1], Default: 30
Returns:	e_code – Type: int

Sets the convergence speed of the IMU Brick. The convergence speed determines how the different sensor measurements are fused.

If the orientation of the IMU Brick is off by 10° and the convergence speed is set to 20°/s, it will take 0.5s until the orientation is corrected. However, if the correct orientation is reached and the convergence speed is too high, the orientation will fluctuate with the fluctuations of the accelerometer and the magnetometer.

If you set the convergence speed to 0, practically only the gyroscope is used to calculate the orientation. This gives very smooth movements, but errors of the gyroscope will not be corrected. If you set the convergence speed to something above 500, practically only the magnetometer and the accelerometer are used to calculate the orientation. In this case the movements are abrupt and the values will fluctuate, but there won't be any errors that accumulate over time.

In an application with high angular velocities, we recommend a high convergence speed, so the errors of the gyroscope can be corrected fast. In applications with only slow movements we recommend a low convergence speed. You can change the convergence speed on the fly. So it is possible (and recommended) to increase the convergence speed before an abrupt movement and decrease it afterwards again.

You might want to play around with the convergence speed in the Brick Viewer to get a feeling for a good value for your application.

int imu_get_convergence_speed(IMU *imu, uint16_t *ret_speed)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_speed – Type: uint16_t, Unit: 1 °/s, Range: [0 to 2¹⁶ - 1], Default: 30
Returns:	e_code – Type: int

Returns the convergence speed as set by imu_set_convergence_speed().

Advanced Functions¶

int imu_get_acceleration(IMU *imu, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_x – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] ret_y – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] ret_z – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

Returns the calibrated acceleration from the accelerometer for the x, y and z axis.

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

int imu_get_magnetic_field(IMU *imu, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_x – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] ret_y – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] ret_z – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

Returns the calibrated magnetic field from the magnetometer for the x, y and z axis.

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

int imu_get_angular_velocity(IMU *imu, int16_t *ret_x, int16_t *ret_y, int16_t *ret_z)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_x – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] ret_y – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] ret_z – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750]
Returns:	e_code – Type: int

Returns the calibrated angular velocity from the gyroscope for the x, y and z axis in °/14.375s (you have to divide by 14.375 to get the value in °/s).

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

int imu_get_all_data(IMU *imu, int16_t *ret_acc_x, int16_t *ret_acc_y, int16_t *ret_acc_z, int16_t *ret_mag_x, int16_t *ret_mag_y, int16_t *ret_mag_z, int16_t *ret_ang_x, int16_t *ret_ang_y, int16_t *ret_ang_z, int16_t *ret_temperature)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_acc_x – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] ret_acc_y – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] ret_acc_z – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] ret_mag_x – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] ret_mag_y – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] ret_mag_z – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] ret_ang_x – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] ret_ang_y – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] ret_ang_z – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] ret_temperature – Type: int16_t, Unit: 1/100 °C, Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

Returns the data from imu_get_acceleration(), imu_get_magnetic_field() and imu_get_angular_velocity() as well as the temperature of the IMU Brick.

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

int imu_get_imu_temperature(IMU *imu, int16_t *ret_temperature)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_temperature – Type: int16_t, Unit: 1/100 °C, Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

Returns the temperature of the IMU Brick.

int imu_set_acceleration_range(IMU *imu, uint8_t range)¶

Parameters:	imu – Type: IMU * range – Type: uint8_t, Range: [0 to 255]
Returns:	e_code – Type: int

Not implemented yet.

int imu_get_acceleration_range(IMU *imu, uint8_t *ret_range)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_range – Type: uint8_t, Range: [0 to 255]
Returns:	e_code – Type: int

Not implemented yet.

int imu_set_magnetometer_range(IMU *imu, uint8_t range)¶

Parameters:	imu – Type: IMU * range – Type: uint8_t, Range: [0 to 255]
Returns:	e_code – Type: int

Not implemented yet.

int imu_get_magnetometer_range(IMU *imu, uint8_t *ret_range)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_range – Type: uint8_t, Range: [0 to 255]
Returns:	e_code – Type: int

Not implemented yet.

int imu_set_calibration(IMU *imu, uint8_t typ, int16_t data[10])¶

Parameters:	imu – Type: IMU * typ – Type: uint8_t, Range: See constants data – Type: int16_t[10], Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

There are several different types that can be calibrated:

Type	Description	Values
0	Accelerometer Gain	`[mul x, mul y, mul z, div x, div y, div z, 0, 0, 0, 0]`
1	Accelerometer Bias	`[bias x, bias y, bias z, 0, 0, 0, 0, 0, 0, 0]`
2	Magnetometer Gain	`[mul x, mul y, mul z, div x, div y, div z, 0, 0, 0, 0]`
3	Magnetometer Bias	`[bias x, bias y, bias z, 0, 0, 0, 0, 0, 0, 0]`
4	Gyroscope Gain	`[mul x, mul y, mul z, div x, div y, div z, 0, 0, 0, 0]`
5	Gyroscope Bias	`[bias xl, bias yl, bias zl, temp l, bias xh, bias yh, bias zh, temp h, 0, 0]`

The calibration via gain and bias is done with the following formula:

new_value = (bias + orig_value) * gain_mul / gain_div

If you really want to write your own calibration software, please keep in mind that you first have to undo the old calibration (set bias to 0 and gain to 1/1) and that you have to average over several thousand values to obtain a usable result in the end.

The gyroscope bias is highly dependent on the temperature, so you have to calibrate the bias two times with different temperatures. The values xl, yl, zl and temp l are the bias for x, y, z and the corresponding temperature for a low temperature. The values xh, yh, zh and temp h are the same for a high temperatures. The temperature difference should be at least 5°C. If you have a temperature where the IMU Brick is mostly used, you should use this temperature for one of the sampling points.

Note

We highly recommend that you use the Brick Viewer to calibrate your IMU Brick.

The following constants are available for this function:

For typ:

IMU_CALIBRATION_TYPE_ACCELEROMETER_GAIN = 0
IMU_CALIBRATION_TYPE_ACCELEROMETER_BIAS = 1
IMU_CALIBRATION_TYPE_MAGNETOMETER_GAIN = 2
IMU_CALIBRATION_TYPE_MAGNETOMETER_BIAS = 3
IMU_CALIBRATION_TYPE_GYROSCOPE_GAIN = 4
IMU_CALIBRATION_TYPE_GYROSCOPE_BIAS = 5

int imu_get_calibration(IMU *imu, uint8_t typ, int16_t ret_data[10])¶

Parameters:	imu – Type: IMU * typ – Type: uint8_t, Range: See constants
Output Parameters:	ret_data – Type: int16_t[10], Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

Returns the calibration for a given type as set by imu_set_calibration().

The following constants are available for this function:

For typ:

IMU_CALIBRATION_TYPE_ACCELEROMETER_GAIN = 0
IMU_CALIBRATION_TYPE_ACCELEROMETER_BIAS = 1
IMU_CALIBRATION_TYPE_MAGNETOMETER_GAIN = 2
IMU_CALIBRATION_TYPE_MAGNETOMETER_BIAS = 3
IMU_CALIBRATION_TYPE_GYROSCOPE_GAIN = 4
IMU_CALIBRATION_TYPE_GYROSCOPE_BIAS = 5

int imu_orientation_calculation_on(IMU *imu)¶

Parameters:	imu – Type: IMU *
Returns:	e_code – Type: int

Turns the orientation calculation of the IMU Brick on.

As default the calculation is on.

New in version 2.0.2 (Firmware).

int imu_orientation_calculation_off(IMU *imu)¶

Parameters:	imu – Type: IMU *
Returns:	e_code – Type: int

Turns the orientation calculation of the IMU Brick off.

If the calculation is off, imu_get_orientation() will return the last calculated value until the calculation is turned on again.

The trigonometric functions that are needed to calculate the orientation are very expensive. We recommend to turn the orientation calculation off if the orientation is not needed, to free calculation time for the sensor fusion algorithm.

As default the calculation is on.

New in version 2.0.2 (Firmware).

int imu_is_orientation_calculation_on(IMU *imu, bool *ret_orientation_calculation_on)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_orientation_calculation_on – Type: bool, Default: true
Returns:	e_code – Type: int

Returns true if the orientation calculation of the IMU Brick is on, false otherwise.

New in version 2.0.2 (Firmware).

int imu_set_spitfp_baudrate_config(IMU *imu, bool enable_dynamic_baudrate, uint32_t minimum_dynamic_baudrate)¶

Parameters:	imu – Type: IMU * enable_dynamic_baudrate – Type: bool, Default: true minimum_dynamic_baudrate – Type: uint32_t, Unit: 1 Bd, Range: [400000 to 2000000], Default: 400000
Returns:	e_code – Type: int

The SPITF protocol can be used with a dynamic baudrate. If the dynamic baudrate is enabled, the Brick will try to adapt the baudrate for the communication between Bricks and Bricklets according to the amount of data that is transferred.

The baudrate will be increased exponentially if lots of data is sent/received and decreased linearly if little data is sent/received.

This lowers the baudrate in applications where little data is transferred (e.g. a weather station) and increases the robustness. If there is lots of data to transfer (e.g. Thermal Imaging Bricklet) it automatically increases the baudrate as needed.

In cases where some data has to transferred as fast as possible every few seconds (e.g. RS485 Bricklet with a high baudrate but small payload) you may want to turn the dynamic baudrate off to get the highest possible performance.

The maximum value of the baudrate can be set per port with the function imu_set_spitfp_baudrate(). If the dynamic baudrate is disabled, the baudrate as set by imu_set_spitfp_baudrate() will be used statically.

New in version 2.3.5 (Firmware).

int imu_get_spitfp_baudrate_config(IMU *imu, bool *ret_enable_dynamic_baudrate, uint32_t *ret_minimum_dynamic_baudrate)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_enable_dynamic_baudrate – Type: bool, Default: true ret_minimum_dynamic_baudrate – Type: uint32_t, Unit: 1 Bd, Range: [400000 to 2000000], Default: 400000
Returns:	e_code – Type: int

Returns the baudrate config, see imu_set_spitfp_baudrate_config().

New in version 2.3.5 (Firmware).

int imu_get_send_timeout_count(IMU *imu, uint8_t communication_method, uint32_t *ret_timeout_count)¶

Parameters:	imu – Type: IMU * communication_method – Type: uint8_t, Range: See constants
Output Parameters:	ret_timeout_count – Type: uint32_t, Range: [0 to 2³² - 1]
Returns:	e_code – Type: int

Returns the timeout count for the different communication methods.

The methods 0-2 are available for all Bricks, 3-7 only for Master Bricks.

This function is mostly used for debugging during development, in normal operation the counters should nearly always stay at 0.

The following constants are available for this function:

For communication_method:

IMU_COMMUNICATION_METHOD_NONE = 0
IMU_COMMUNICATION_METHOD_USB = 1
IMU_COMMUNICATION_METHOD_SPI_STACK = 2
IMU_COMMUNICATION_METHOD_CHIBI = 3
IMU_COMMUNICATION_METHOD_RS485 = 4
IMU_COMMUNICATION_METHOD_WIFI = 5
IMU_COMMUNICATION_METHOD_ETHERNET = 6
IMU_COMMUNICATION_METHOD_WIFI_V2 = 7

New in version 2.3.3 (Firmware).

int imu_set_spitfp_baudrate(IMU *imu, char bricklet_port, uint32_t baudrate)¶

Parameters:	imu – Type: IMU * bricklet_port – Type: char, Range: ['a' to 'b'] baudrate – Type: uint32_t, Unit: 1 Bd, Range: [400000 to 2000000], Default: 1400000
Returns:	e_code – Type: int

Sets the baudrate for a specific Bricklet port.

If you want to increase the throughput of Bricklets you can increase the baudrate. If you get a high error count because of high interference (see imu_get_spitfp_error_count()) you can decrease the baudrate.

If the dynamic baudrate feature is enabled, the baudrate set by this function corresponds to the maximum baudrate (see imu_set_spitfp_baudrate_config()).

Regulatory testing is done with the default baudrate. If CE compatibility or similar is necessary in your applications we recommend to not change the baudrate.

New in version 2.3.3 (Firmware).

int imu_get_spitfp_baudrate(IMU *imu, char bricklet_port, uint32_t *ret_baudrate)¶

Parameters:	imu – Type: IMU * bricklet_port – Type: char, Range: ['a' to 'b']
Output Parameters:	ret_baudrate – Type: uint32_t, Unit: 1 Bd, Range: [400000 to 2000000], Default: 1400000
Returns:	e_code – Type: int

Returns the baudrate for a given Bricklet port, see imu_set_spitfp_baudrate().

New in version 2.3.3 (Firmware).

int imu_get_spitfp_error_count(IMU *imu, char bricklet_port, uint32_t *ret_error_count_ack_checksum, uint32_t *ret_error_count_message_checksum, uint32_t *ret_error_count_frame, uint32_t *ret_error_count_overflow)¶

Parameters:	imu – Type: IMU * bricklet_port – Type: char, Range: ['a' to 'b']
Output Parameters:	ret_error_count_ack_checksum – Type: uint32_t, Range: [0 to 2³² - 1] ret_error_count_message_checksum – Type: uint32_t, Range: [0 to 2³² - 1] ret_error_count_frame – Type: uint32_t, Range: [0 to 2³² - 1] ret_error_count_overflow – Type: uint32_t, Range: [0 to 2³² - 1]
Returns:	e_code – Type: int

Returns the error count for the communication between Brick and Bricklet.

The errors are divided into

ACK checksum errors,
message checksum errors,
framing errors and
overflow errors.

The errors counts are for errors that occur on the Brick side. All Bricklets have a similar function that returns the errors on the Bricklet side.

New in version 2.3.3 (Firmware).

int imu_enable_status_led(IMU *imu)¶

Parameters:	imu – Type: IMU *
Returns:	e_code – Type: int

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.

New in version 2.3.1 (Firmware).

int imu_disable_status_led(IMU *imu)¶

Parameters:	imu – Type: IMU *
Returns:	e_code – Type: int

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.

New in version 2.3.1 (Firmware).

int imu_is_status_led_enabled(IMU *imu, bool *ret_enabled)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_enabled – Type: bool, Default: true
Returns:	e_code – Type: int

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

New in version 2.3.1 (Firmware).

int imu_get_chip_temperature(IMU *imu, int16_t *ret_temperature)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_temperature – Type: int16_t, Unit: 1/10 °C, Range: [-2¹⁵ to 2¹⁵ - 1]
Returns:	e_code – Type: int

Returns the temperature 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_reset(IMU *imu)¶

Parameters:	imu – Type: IMU *
Returns:	e_code – Type: int

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_get_identity(IMU *imu, 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)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_uid – Type: char[8] ret_connected_uid – Type: char[8] ret_position – Type: char, Range: ['0' to '8'] ret_hardware_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255] ret_firmware_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255] ret_device_identifier – Type: uint16_t, Range: [0 to 2¹⁶ - 1]
Returns:	e_code – Type: int

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 is the position in the stack from '0' (bottom) to '8' (top).

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_register_callback(IMU *imu, int16_t callback_id, void (*function)(void), void *user_data)¶

Parameters:	imu – Type: IMU * callback_id – Type: int16_t function – Type: void ()(void) user_data* – Type: void *

Registers the given function with the given callback_id. The user_data will be passed as the last parameter to the function.

The available callback IDs with corresponding function signatures are listed below.

int imu_set_acceleration_period(IMU *imu, uint32_t period)¶

Parameters:	imu – Type: IMU * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

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

int imu_get_acceleration_period(IMU *imu, uint32_t *ret_period)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

Returns the period as set by imu_set_acceleration_period().

int imu_set_magnetic_field_period(IMU *imu, uint32_t period)¶

Parameters:	imu – Type: IMU * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

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

int imu_get_magnetic_field_period(IMU *imu, uint32_t *ret_period)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

Returns the period as set by imu_set_magnetic_field_period().

int imu_set_angular_velocity_period(IMU *imu, uint32_t period)¶

Parameters:	imu – Type: IMU * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

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

int imu_get_angular_velocity_period(IMU *imu, uint32_t *ret_period)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

Returns the period as set by imu_set_angular_velocity_period().

int imu_set_all_data_period(IMU *imu, uint32_t period)¶

Parameters:	imu – Type: IMU * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

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

int imu_get_all_data_period(IMU *imu, uint32_t *ret_period)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

Returns the period as set by imu_set_all_data_period().

int imu_set_orientation_period(IMU *imu, uint32_t period)¶

Parameters:	imu – Type: IMU * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

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

int imu_get_orientation_period(IMU *imu, uint32_t *ret_period)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

Returns the period as set by imu_set_orientation_period().

int imu_set_quaternion_period(IMU *imu, uint32_t period)¶

Parameters:	imu – Type: IMU * period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

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

int imu_get_quaternion_period(IMU *imu, uint32_t *ret_period)¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_period – Type: uint32_t, Unit: 1 ms, Range: [0 to 2³² - 1], Default: 0
Returns:	e_code – Type: int

Returns the period as set by imu_set_quaternion_period().

Callbacks¶

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the imu_register_callback() function:

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

imu_register_callback(&imu,
                      IMU_CALLBACK_EXAMPLE,
                      (void (*)(void))my_callback,
                      NULL);

The available constants with corresponding 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_CALLBACK_ACCELERATION¶

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

Callback Parameters:	x – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] y – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] z – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1] user_data – Type: void *

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

IMU_CALLBACK_MAGNETIC_FIELD¶

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

Callback Parameters:	x – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] y – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] z – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1] user_data – Type: void *

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

IMU_CALLBACK_ANGULAR_VELOCITY¶

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

Callback Parameters:	x – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] y – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] z – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750] user_data – Type: void *

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

IMU_CALLBACK_ALL_DATA¶

void callback(int16_t acc_x, int16_t acc_y, int16_t acc_z, int16_t mag_x, int16_t mag_y, int16_t mag_z, int16_t ang_x, int16_t ang_y, int16_t ang_z, int16_t temperature, void *user_data)

Callback Parameters:

acc_x – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1]
acc_y – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1]
acc_z – Type: int16_t, Unit: 1/1000 gₙ, Range: [-2¹⁵ to 2¹⁵ - 1]
mag_x – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1]
mag_y – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1]
mag_z – Type: int16_t, Unit: 1/10 µT, Range: [-2¹⁵ to 2¹⁵ - 1]
ang_x – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750]
ang_y – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750]
ang_z – Type: int16_t, Unit: 8/115 °/s, Range: [-28750 to 28750]
temperature – Type: int16_t, Unit: 1/100 °C, Range: [-2¹⁵ to 2¹⁵ - 1]
user_data – Type: void *

This callback is triggered periodically with the period that is set by imu_set_all_data_period(). The parameters are the acceleration, the magnetic field and the angular velocity for the x, y and z axis as well as the temperature of the IMU Brick.

IMU_CALLBACK_ORIENTATION¶

void callback(int16_t roll, int16_t pitch, int16_t yaw, void *user_data)

Callback Parameters:	roll – Type: int16_t, Unit: 1/100 °, Range: [-18000 to 18000] pitch – Type: int16_t, Unit: 1/100 °, Range: [-18000 to 18000] yaw – Type: int16_t, Unit: 1/100 °, Range: [-18000 to 18000] user_data – Type: void *

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

IMU_CALLBACK_QUATERNION¶

void callback(float x, float y, float z, float w, void *user_data)

Callback Parameters:	x – Type: float, Range: [-1.0f to 1.0f] y – Type: float, Range: [-1.0f to 1.0f] z – Type: float, Range: [-1.0f to 1.0f] w – Type: float, Range: [-1.0f to 1.0f] user_data – Type: void *

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

Virtual Functions¶

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

int imu_get_api_version(IMU *imu, uint8_t ret_api_version[3])¶

Parameters:	imu – Type: IMU *
Output Parameters:	ret_api_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255]
Returns:	e_code – Type: int

Returns the version of the API definition 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_get_response_expected(IMU *imu, uint8_t function_id, bool *ret_response_expected)¶

Parameters:	imu – Type: IMU * function_id – Type: uint8_t, Range: See constants
Output Parameters:	ret_response_expected – Type: bool
Returns:	e_code – Type: int

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_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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

IMU_FUNCTION_LEDS_ON = 8
IMU_FUNCTION_LEDS_OFF = 9
IMU_FUNCTION_SET_ACCELERATION_RANGE = 11
IMU_FUNCTION_SET_MAGNETOMETER_RANGE = 13
IMU_FUNCTION_SET_CONVERGENCE_SPEED = 15
IMU_FUNCTION_SET_CALIBRATION = 17
IMU_FUNCTION_SET_ACCELERATION_PERIOD = 19
IMU_FUNCTION_SET_MAGNETIC_FIELD_PERIOD = 21
IMU_FUNCTION_SET_ANGULAR_VELOCITY_PERIOD = 23
IMU_FUNCTION_SET_ALL_DATA_PERIOD = 25
IMU_FUNCTION_SET_ORIENTATION_PERIOD = 27
IMU_FUNCTION_SET_QUATERNION_PERIOD = 29
IMU_FUNCTION_ORIENTATION_CALCULATION_ON = 37
IMU_FUNCTION_ORIENTATION_CALCULATION_OFF = 38
IMU_FUNCTION_SET_SPITFP_BAUDRATE_CONFIG = 231
IMU_FUNCTION_SET_SPITFP_BAUDRATE = 234
IMU_FUNCTION_ENABLE_STATUS_LED = 238
IMU_FUNCTION_DISABLE_STATUS_LED = 239
IMU_FUNCTION_RESET = 243
IMU_FUNCTION_WRITE_BRICKLET_PLUGIN = 246

int imu_set_response_expected(IMU *imu, uint8_t function_id, bool response_expected)¶

Parameters:	imu – Type: IMU * function_id – Type: uint8_t, Range: See constants response_expected – Type: bool
Returns:	e_code – Type: int

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.

The following constants are available for this function:

For function_id:

IMU_FUNCTION_LEDS_ON = 8
IMU_FUNCTION_LEDS_OFF = 9
IMU_FUNCTION_SET_ACCELERATION_RANGE = 11
IMU_FUNCTION_SET_MAGNETOMETER_RANGE = 13
IMU_FUNCTION_SET_CONVERGENCE_SPEED = 15
IMU_FUNCTION_SET_CALIBRATION = 17
IMU_FUNCTION_SET_ACCELERATION_PERIOD = 19
IMU_FUNCTION_SET_MAGNETIC_FIELD_PERIOD = 21
IMU_FUNCTION_SET_ANGULAR_VELOCITY_PERIOD = 23
IMU_FUNCTION_SET_ALL_DATA_PERIOD = 25
IMU_FUNCTION_SET_ORIENTATION_PERIOD = 27
IMU_FUNCTION_SET_QUATERNION_PERIOD = 29
IMU_FUNCTION_ORIENTATION_CALCULATION_ON = 37
IMU_FUNCTION_ORIENTATION_CALCULATION_OFF = 38
IMU_FUNCTION_SET_SPITFP_BAUDRATE_CONFIG = 231
IMU_FUNCTION_SET_SPITFP_BAUDRATE = 234
IMU_FUNCTION_ENABLE_STATUS_LED = 238
IMU_FUNCTION_DISABLE_STATUS_LED = 239
IMU_FUNCTION_RESET = 243
IMU_FUNCTION_WRITE_BRICKLET_PLUGIN = 246

int imu_set_response_expected_all(IMU *imu, bool response_expected)¶

Parameters:	imu – Type: IMU * response_expected – Type: bool
Returns:	e_code – Type: int

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

Internal Functions¶

Internal functions are used for maintenance tasks such as flashing a new firmware of changing the UID of a Bricklet. These task should be performed using Brick Viewer instead of using the internal functions directly.

int imu_get_protocol1_bricklet_name(IMU *imu, char port, uint8_t *ret_protocol_version, uint8_t ret_firmware_version[3], char ret_name[40])¶

Parameters:	imu – Type: IMU * port – Type: char, Range: ['a' to 'b']
Output Parameters:	ret_protocol_version – Type: uint8_t, Range: [0 to 255] ret_firmware_version – Type: uint8_t[3] 0: major – Type: uint8_t, Range: [0 to 255] 1: minor – Type: uint8_t, Range: [0 to 255] 2: revision – Type: uint8_t, Range: [0 to 255] ret_name – Type: char[40]
Returns:	e_code – Type: int

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_write_bricklet_plugin(IMU *imu, char port, uint8_t offset, uint8_t chunk[32])¶

Parameters:	imu – Type: IMU * port – Type: char, Range: ['a' to 'b'] offset – Type: uint8_t, Range: [0 to 255] chunk – Type: uint8_t[32], Range: [0 to 255]
Returns:	e_code – Type: int

Writes 32 bytes of firmware to the bricklet attached at the given port. The bytes are written to the position offset * 32.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

int imu_read_bricklet_plugin(IMU *imu, char port, uint8_t offset, uint8_t ret_chunk[32])¶

Parameters:	imu – Type: IMU * port – Type: char, Range: ['a' to 'b'] offset – Type: uint8_t, Range: [0 to 255]
Output Parameters:	ret_chunk – Type: uint8_t[32], Range: [0 to 255]
Returns:	e_code – Type: int

Reads 32 bytes of firmware from the bricklet attached at the given port. The bytes are read starting at the position offset * 32.

This function is used by Brick Viewer during flashing. It should not be necessary to call it in a normal user program.

Constants¶

IMU_DEVICE_IDENTIFIER¶

This constant is used to identify a IMU Brick.

The imu_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.

IMU_DEVICE_DISPLAY_NAME¶: This constant represents the human readable name of a IMU Brick.