Python - 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 Python 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 Python API bindings is part of their general description.

Examples

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

Callback

Download (example_callback.py)

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#!/usr/bin/env python
# -*- coding: utf-8 -*-  

HOST = "localhost"
PORT = 4223
UID = "6ww9bv" # Change to your UID

from tinkerforge.ip_connection import IPConnection
from tinkerforge.brick_imu_v2 import IMUV2

# All Data callback
def cb_all_data(acceleration, magnetic_field, angular_velocity, 
                euler_angle, quaternion, linear_acceleration, 
                gravity_vector, temperature, calibration_status):
    print u'''
Acceleration        x: {:.2f} y: {:.2f} z: {:.2f} m/s²
Magnetic Field      x: {:.2f} y: {:.2f} z: {:.2f} µT
Angular Velocity    x: {:.2f} y: {:.2f} z: {:.2f} °/s
Euler Angles        x: {:.2f} y: {:.2f} z: {:.2f} °
Quaternion          x: {:.2f} y: {:.2f} z: {:.2f}
Linear Acceleration x: {:.2f} y: {:.2f} z: {:.2f} m/s²
Gravity Vector      x: {:.2f} y: {:.2f} z: {:.2f} m/s²
Temperature:        {} °C
calibration Status: {}
'''.format(acceleration[0]/100.0,          acceleration[1]/100.0,          acceleration[2]/100.0,
           magnetic_field[0]/16.0,         magnetic_field[1]/16.0,         magnetic_field[2]/16.0, 
           angular_velocity[0]/16.0,       angular_velocity[1]/16.0,       angular_velocity[2]/16.0,
           euler_angle[0]/16.0,            euler_angle[1]/16.0,            euler_angle[2]/16.0, 
           quaternion[0]/(float(2**14-1)), quaternion[1]/(float(2**14-1)), quaternion[2]/(float(2**14-1)),
           linear_acceleration[0]/100.0,   linear_acceleration[1]/100.0,   linear_acceleration[2]/100.0, 
           gravity_vector[0]/100.0,        gravity_vector[1]/100.0,        gravity_vector[2]/100.0, 
           temperature, calibration_status)

if __name__ == "__main__":
    ipcon = IPConnection() # Create IP connection
    imu = IMUV2(UID, ipcon) # Create device object

    ipcon.connect(HOST, PORT) # Connect to brickd
    # Don't use device before ipcon is connected

    # Set period for quaternion callback to 100ms
    imu.set_all_data_period(100)

    # Register All Data callback
    imu.register_callback(imu.CALLBACK_ALL_DATA, cb_all_data)

    raw_input('Press key to exit\n') # Use input() in Python 3
    ipcon.disconnect()

API

Generally, every method of the Python bindings can throw an tinkerforge.ip_connection.Error exception that has a value and a description property. value can have different values:

  • Error.TIMEOUT = -1
  • Error.ALREADY_CONNECTED = -7
  • Error.NOT_CONNECTED = -8
  • Error.INVALID_PARAMETER = -9
  • Error.NOT_SUPPORTED = -10
  • Error.UNKNOWN_ERROR_CODE = -11

All methods listed below are thread-safe.

Basic Functions

IMUV2(uid, ipcon)
Parameters:
  • uid -- string
  • ipcon -- IPConnection

Creates an object with the unique device ID uid:

imu_v2 = IMUV2("YOUR_DEVICE_UID", ipcon)

This object can then be used after the IP Connection is connected (see examples above).

IMUV2.get_all_data()
Return type:([int, int, int], [int, int, int], [int, int, int], [int, int, int], [int, int, int, int], [int, int, int], [int, int, int], int, int)

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().

The returned namedtuple has the variables acceleration, magnetic_field, angular_velocity, euler_angle, quaternion, linear_acceleration, gravity_vector, temperature and calibration_status.

IMUV2.leds_on()
Return type:None

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

IMUV2.leds_off()
Return type:None

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

IMUV2.are_leds_on()
Return type:bool

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

Advanced Functions

IMUV2.get_acceleration()
Return type:(int, int, int)

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().

The returned namedtuple has the variables x, y and z.

IMUV2.get_magnetic_field()
Return type:(int, int, int)

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().

The returned namedtuple has the variables x, y and z.

IMUV2.get_angular_velocity()
Return type:(int, int, int)

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().

The returned namedtuple has the variables x, y and z.

IMUV2.get_temperature()
Return type:int

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

IMUV2.get_orientation()
Return type:(int, int, int)

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().

The returned namedtuple has the variables heading, roll and pitch.

IMUV2.get_linear_acceleration()
Return type:(int, int, int)

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().

The returned namedtuple has the variables x, y and z.

IMUV2.get_gravity_vector()
Return type:(int, int, int)

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().

The returned namedtuple has the variables x, y and z.

IMUV2.get_quaternion()
Return type:(int, int, int, int)

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().

The returned namedtuple has the variables w, x, y and z.

IMUV2.save_calibration()
Return type: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.

IMUV2.get_api_version()
Return type:[int, int, int]

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.

IMUV2.get_response_expected(function_id)
Parameters:function_id -- int
Return type:bool

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 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 set_response_expected() for the list of function ID constants available for this function.

IMUV2.set_response_expected(function_id, response_expected)
Parameters:
  • function_id -- int
  • response_expected -- bool
Return type:

None

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 constants are available for this function:

  • IMUV2.FUNCTION_LEDS_ON = 10
  • IMUV2.FUNCTION_LEDS_OFF = 11
  • IMUV2.FUNCTION_SET_ACCELERATION_PERIOD = 14
  • IMUV2.FUNCTION_SET_MAGNETIC_FIELD_PERIOD = 16
  • IMUV2.FUNCTION_SET_ANGULAR_VELOCITY_PERIOD = 18
  • IMUV2.FUNCTION_SET_TEMPERATURE_PERIOD = 20
  • IMUV2.FUNCTION_SET_ORIENTATION_PERIOD = 22
  • IMUV2.FUNCTION_SET_LINEAR_ACCELERATION_PERIOD = 24
  • IMUV2.FUNCTION_SET_GRAVITY_VECTOR_PERIOD = 26
  • IMUV2.FUNCTION_SET_QUATERNION_PERIOD = 28
  • IMUV2.FUNCTION_SET_ALL_DATA_PERIOD = 30
  • IMUV2.FUNCTION_ENABLE_STATUS_LED = 238
  • IMUV2.FUNCTION_DISABLE_STATUS_LED = 239
  • IMUV2.FUNCTION_RESET = 243
IMUV2.set_response_expected_all(response_expected)
Parameters:response_expected -- bool
Return type:None

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

IMUV2.enable_status_led()
Return type:None

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.

IMUV2.disable_status_led()
Return type:None

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.

IMUV2.is_status_led_enabled()
Return type:bool

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

IMUV2.get_protocol1_bricklet_name(port)
Parameters:port -- chr
Return type:(int, [int, int, int], str)

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.

The returned namedtuple has the variables protocol_version, firmware_version and name.

IMUV2.get_chip_temperature()
Return type:int

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.

IMUV2.reset()
Return type:None

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!

IMUV2.get_identity()
Return type:(str, str, chr, [int, int, int], [int, int, int], 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 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.

The returned namedtuple has the variables uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

IMUV2.register_callback(id, callback)
Parameters:
  • id -- int
  • callback -- callable
Return type:

None

Registers a callback with ID id to the function callback. The available IDs with corresponding function signatures are listed below.

IMUV2.set_acceleration_period(period)
Parameters:period -- int
Return type:None

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.

IMUV2.get_acceleration_period()
Return type:int

Returns the period as set by set_acceleration_period().

IMUV2.set_magnetic_field_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_magnetic_field_period()
Return type:int

Returns the period as set by set_magnetic_field_period().

IMUV2.set_angular_velocity_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_angular_velocity_period()
Return type:int

Returns the period as set by set_angular_velocity_period().

IMUV2.set_temperature_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_temperature_period()
Return type:int

Returns the period as set by set_temperature_period().

IMUV2.set_orientation_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_orientation_period()
Return type:int

Returns the period as set by set_orientation_period().

IMUV2.set_linear_acceleration_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_linear_acceleration_period()
Return type:int

Returns the period as set by set_linear_acceleration_period().

IMUV2.set_gravity_vector_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_gravity_vector_period()
Return type:int

Returns the period as set by set_gravity_vector_period().

IMUV2.set_quaternion_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_quaternion_period()
Return type:int

Returns the period as set by set_quaternion_period().

IMUV2.set_all_data_period(period)
Parameters:period -- int
Return type:None

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

IMUV2.get_all_data_period()
Return type:int

Returns the period as set by 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 register_callback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:

def my_callback(param):
    print(param)

imu_v2.register_callback(IMUV2.CALLBACK_EXAMPLE, my_callback)

The available constants with inherent number and type of parameters 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.

IMUV2.CALLBACK_ACCELERATION
Parameters:
  • x -- int
  • y -- int
  • z -- int

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

IMUV2.CALLBACK_MAGNETIC_FIELD
Parameters:
  • x -- int
  • y -- int
  • z -- int

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

IMUV2.CALLBACK_ANGULAR_VELOCITY
Parameters:
  • x -- int
  • y -- int
  • z -- int

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

IMUV2.CALLBACK_TEMPERATURE
Parameters:temperature -- int

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

IMUV2.CALLBACK_LINEAR_ACCELERATION
Parameters:
  • x -- int
  • y -- int
  • z -- int

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

IMUV2.CALLBACK_GRAVITY_VECTOR
Parameters:
  • x -- int
  • y -- int
  • z -- int

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

IMUV2.CALLBACK_ORIENTATION
Parameters:
  • heading -- int
  • roll -- int
  • pitch -- int

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

IMUV2.CALLBACK_QUATERNION
Parameters:
  • w -- int
  • x -- int
  • y -- int
  • z -- int

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

IMUV2.CALLBACK_ALL_DATA
Parameters:
  • acceleration -- [int, int, int]
  • magnetic_field -- [int, int, int]
  • angular_velocity -- [int, int, int]
  • euler_angle -- [int, int, int]
  • quaternion -- [int, int, int, int]
  • linear_acceleration -- [int, int, int]
  • gravity_vector -- [int, int, int]
  • temperature -- int
  • calibration_status -- int

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

Constants

IMUV2.DEVICE_IDENTIFIER

This constant is used to identify a IMU Brick 2.0.

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

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