Modbus - 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 Modbus protocol for the IMU Brick 2.0. General information and technical specifications for the IMU Brick 2.0 are summarized in its hardware description.

API

A general description of the Modbus protocol structure can be found here.

Basic Functions

BrickIMUV2.get_all_data
Function ID:

9

Request:

empty payload

Response:
  • acceleration -- int16[3]
  • magnetic_field -- int16[3]
  • angular_velocity -- int16[3]
  • euler_angle -- int16[3]
  • quaternion -- int16[4]
  • linear_acceleration -- int16[3]
  • gravity_vector -- int16[3]
  • temperature -- int8
  • calibration_status -- uint8

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 CALLBACK_ALL_DATA and set the period with set_all_data_period.

BrickIMUV2.leds_on
Function ID:10
Request:empty payload
Response:no response

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

BrickIMUV2.leds_off
Function ID:11
Request:empty payload
Response:no response

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

BrickIMUV2.are_leds_on
Function ID:

12

Request:

empty payload

Response:
  • leds -- bool

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

Advanced Functions

BrickIMUV2.get_acceleration
Function ID:

1

Request:

empty payload

Response:
  • x -- int16
  • y -- int16
  • z -- int16

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 CALLBACK_ACCELERATION and set the period with set_acceleration_period.

BrickIMUV2.get_magnetic_field
Function ID:

2

Request:

empty payload

Response:
  • x -- int16
  • y -- int16
  • z -- int16

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 CALLBACK_MAGNETIC_FIELD and set the period with set_magnetic_field_period.

BrickIMUV2.get_angular_velocity
Function ID:

3

Request:

empty payload

Response:
  • x -- int16
  • y -- int16
  • z -- int16

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 CALLBACK_ANGULAR_VELOCITY and set the period with set_angular_velocity_period.

BrickIMUV2.get_temperature
Function ID:

4

Request:

empty payload

Response:
  • temperature -- int8

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

BrickIMUV2.get_orientation
Function ID:

5

Request:

empty payload

Response:
  • heading -- int16
  • roll -- int16
  • pitch -- int16

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 CALLBACK_ORIENTATION and set the period with set_orientation_period.

BrickIMUV2.get_linear_acceleration
Function ID:

6

Request:

empty payload

Response:
  • x -- int16
  • y -- int16
  • z -- int16

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 get_gravity_vector.

If you want to get the linear acceleration periodically, it is recommended to use the callback CALLBACK_LINEAR_ACCELERATION and set the period with set_linear_acceleration_period.

BrickIMUV2.get_gravity_vector
Function ID:

7

Request:

empty payload

Response:
  • x -- int16
  • y -- int16
  • z -- int16

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 get_linear_acceleration.

If you want to get the gravity vector periodically, it is recommended to use the callback CALLBACK_GRAVITY_VECTOR and set the period with set_gravity_vector_period.

BrickIMUV2.get_quaternion
Function ID:

8

Request:

empty payload

Response:
  • w -- int16
  • x -- int16
  • y -- int16
  • z -- int16

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 CALLBACK_QUATERNION and set the period with set_quaternion_period.

BrickIMUV2.save_calibration
Function ID:

13

Request:

empty payload

Response:
  • calibration_done -- bool

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.

BrickIMUV2.enable_status_led
Function ID:238
Request:empty payload
Response:no response

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.

BrickIMUV2.disable_status_led
Function ID:239
Request:empty payload
Response:no response

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.

BrickIMUV2.is_status_led_enabled
Function ID:

240

Request:

empty payload

Response:
  • enabled -- bool

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

BrickIMUV2.get_protocol1_bricklet_name
Function ID:

241

Request:
  • port -- char
Response:
  • protocol_version -- uint8
  • firmware_version -- uint8[3]
  • name -- char[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.

BrickIMUV2.get_chip_temperature
Function ID:

242

Request:

empty payload

Response:
  • temperature -- int16

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.

BrickIMUV2.reset
Function ID:243
Request:empty payload
Response:no response

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!

BrickIMUV2.get_identity
Function ID:

255

Request:

empty payload

Response:
  • uid -- char[8]
  • connected_uid -- char[8]
  • position -- char
  • hardware_version -- uint8[3]
  • firmware_version -- uint8[3]
  • device_identifier -- uint16

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

Callback Configuration Functions

BrickIMUV2.set_acceleration_period
Function ID:

14

Request:
  • period -- uint32
Response:

no response

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

The default value is 0.

BrickIMUV2.get_acceleration_period
Function ID:

15

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_acceleration_period.

BrickIMUV2.set_magnetic_field_period
Function ID:

16

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_magnetic_field_period
Function ID:

17

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_magnetic_field_period.

BrickIMUV2.set_angular_velocity_period
Function ID:

18

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_angular_velocity_period
Function ID:

19

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_angular_velocity_period.

BrickIMUV2.set_temperature_period
Function ID:

20

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_temperature_period
Function ID:

21

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_temperature_period.

BrickIMUV2.set_orientation_period
Function ID:

22

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_orientation_period
Function ID:

23

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_orientation_period.

BrickIMUV2.set_linear_acceleration_period
Function ID:

24

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_linear_acceleration_period
Function ID:

25

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_linear_acceleration_period.

BrickIMUV2.set_gravity_vector_period
Function ID:

26

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_gravity_vector_period
Function ID:

27

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_gravity_vector_period.

BrickIMUV2.set_quaternion_period
Function ID:

28

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_quaternion_period
Function ID:

29

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_quaternion_period.

BrickIMUV2.set_all_data_period
Function ID:

30

Request:
  • period -- uint32
Response:

no response

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

BrickIMUV2.get_all_data_period
Function ID:

31

Request:

empty payload

Response:
  • period -- uint32

Returns the period as set by set_all_data_period.

Callbacks

BrickIMUV2.CALLBACK_ACCELERATION
Function ID:

32

Response:
  • x -- int16
  • y -- int16
  • z -- int16

This callback is triggered periodically with the period that is set by set_acceleration_period. The response values are the acceleration for the x, y and z axis.

BrickIMUV2.CALLBACK_MAGNETIC_FIELD
Function ID:

33

Response:
  • x -- int16
  • y -- int16
  • z -- int16

This callback is triggered periodically with the period that is set by set_magnetic_field_period. The response values are the magnetic field for the x, y and z axis.

BrickIMUV2.CALLBACK_ANGULAR_VELOCITY
Function ID:

34

Response:
  • x -- int16
  • y -- int16
  • z -- int16

This callback is triggered periodically with the period that is set by set_angular_velocity_period. The response values are the angular velocity for the x, y and z axis.

BrickIMUV2.CALLBACK_TEMPERATURE
Function ID:

35

Response:
  • temperature -- int8

This callback is triggered periodically with the period that is set by set_temperature_period. The response value is the temperature.

BrickIMUV2.CALLBACK_LINEAR_ACCELERATION
Function ID:

36

Response:
  • x -- int16
  • y -- int16
  • z -- int16

This callback is triggered periodically with the period that is set by set_linear_acceleration_period. The response values are the linear acceleration for the x, y and z axis.

BrickIMUV2.CALLBACK_GRAVITY_VECTOR
Function ID:

37

Response:
  • x -- int16
  • y -- int16
  • z -- int16

This callback is triggered periodically with the period that is set by set_gravity_vector_period. The response values gravity vector for the x, y and z axis.

BrickIMUV2.CALLBACK_ORIENTATION
Function ID:

38

Response:
  • heading -- int16
  • roll -- int16
  • pitch -- int16

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

BrickIMUV2.CALLBACK_QUATERNION
Function ID:

39

Response:
  • w -- int16
  • x -- int16
  • y -- int16
  • z -- int16

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

BrickIMUV2.CALLBACK_ALL_DATA
Function ID:

40

Response:
  • acceleration -- int16[3]
  • magnetic_field -- int16[3]
  • angular_velocity -- int16[3]
  • euler_angle -- int16[3]
  • quaternion -- int16[4]
  • linear_acceleration -- int16[3]
  • gravity_vector -- int16[3]
  • temperature -- int8
  • calibration_status -- uint8

This callback is triggered periodically with the period that is set by set_all_data_period. The response values are as for get_all_data.

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