Shell - IMU Brick

This is the description of the Shell 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 Shell API bindings is part of their general description.

Examples

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

Simple

Download (example-simple.sh)

1
2
3
4
5
6
7
8
#!/bin/sh
# connects to localhost:4223 by default, use --host and --port to change it

# change to your UID
uid=XYZ

# get current color
tinkerforge call imu-brick $uid get-quaternion

Callback

Download (example-callback.sh)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
#!/bin/sh
# connects to localhost:4223 by default, use --host and --port to change it

# change to your UID
uid=XYZ

# set period for quaternion callback to 1s (1000ms)
tinkerforge call imu-brick $uid set-quaternion-period 1000

# handle incoming quaternion callbacks
tinkerforge dispatch imu-brick $uid quaternion

API

Possible exit codes for all tinkerforge commands are:

  • 1: interrupted (ctrl+c)
  • 2: syntax error
  • 21: Python 2.5 or newer is required
  • 22: Python argparse module is missing
  • 23: socket error
  • 24: other exception
  • 25: invalid placeholder in format string
  • 26: authentication error
  • 201: timeout occurred
  • 209: invalid argument value
  • 210: function is not supported
  • 211: unknown error

Command Structure

The common options of the call and dispatch commands are documented here. The specific command structure is shown below.

tinkerforge call imu-brick [<option>..] <uid> <function> [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The call command is used to call a function of the IMU Brick. It can take several options:

  • --help shows help for the specific call command and exits
  • --list-functions shows a list of known functions of the IMU Brick and exits
tinkerforge dispatch imu-brick [<option>..] <uid> <callback>
Parameters:
  • <uid> -- string
  • <callback> -- string

The dispatch command is used to dispatch a callback of the IMU Brick. It can take several options:

  • --help shows help for the specific dispatch command and exits
  • --list-callbacks shows a list of known callbacks of the IMU Brick and exits
tinkerforge call imu-brick <uid> <function> [<option>..] [<argument>..]
Parameters:
  • <uid> -- string
  • <function> -- string

The <function> to be called can take different options depending of its kind. All functions can take the following options:

  • --help shows help for the specific function and exits

Getter functions can take the following options:

  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Setter functions can take the following options:

  • --expect-response requests response and waits for it

The --expect-response option for setter functions allows to detect timeouts and other error conditions calls of setters as well. The device will then send a response for this purpose. If this option is not given for a setter function then no response is send and errors are silently ignored, because they cannot be detected.

tinkerforge dispatch imu-brick <uid> <callback> [<option>..]
Parameters:
  • <uid> -- string
  • <callback> -- string

The <callback> to be dispatched can take several options:

  • --help shows help for the specific callback and exits
  • --execute <command> shell command line to execute for each incoming response (see section about output formatting for details)

Basic Functions

tinkerforge call imu-brick <uid> get-orientation
Output:
  • roll -- int
  • pitch -- int
  • yaw -- int

Returns the current orientation (roll, pitch, yaw) of the IMU Brick as Euler angles in one-hundredth degree. 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 callback orientation and set the period with set-orientation-period.

tinkerforge call imu-brick <uid> get-quaternion
Output:
  • x -- float
  • y -- float
  • z -- float
  • w -- float

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 callback quaternion and set the period with set-quaternion-period.

tinkerforge call imu-brick <uid> leds-on
Output:no output

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

tinkerforge call imu-brick <uid> leds-off
Output:no output

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

tinkerforge call imu-brick <uid> are-leds-on
Output:
  • leds -- bool

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

tinkerforge call imu-brick <uid> set-convergence-speed <speed>
Parameters:
  • <speed> -- int
Output:

no output

Sets the convergence speed of the IMU Brick in °/s. 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.

The default value is 30.

tinkerforge call imu-brick <uid> get-convergence-speed
Output:
  • speed -- int

Returns the convergence speed as set by set-convergence-speed.

Advanced Functions

tinkerforge call imu-brick <uid> get-acceleration
Output:
  • x -- int
  • y -- int
  • z -- int

Returns the calibrated acceleration from the accelerometer for the x, y and z axis in mG (G/1000, 1G = 9.80605m/s²).

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

tinkerforge call imu-brick <uid> get-magnetic-field
Output:
  • x -- int
  • y -- int
  • z -- int

Returns the calibrated magnetic field from the magnetometer for the x, y and z axis in mG (Milligauss or Nanotesla).

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

tinkerforge call imu-brick <uid> get-angular-velocity
Output:
  • x -- int
  • y -- int
  • z -- 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 callback angular-velocity and set the period with set-angular-velocity-period.

tinkerforge call imu-brick <uid> get-all-data
Output:
  • acc-x -- int
  • acc-y -- int
  • acc-z -- int
  • mag-x -- int
  • mag-y -- int
  • mag-z -- int
  • ang-x -- int
  • ang-y -- int
  • ang-z -- int
  • temperature -- int

Returns the data from get-acceleration, get-magnetic-field and get-angular-velocity as well as the temperature of the IMU Brick.

The temperature is given in °C/100.

If you want to get the data periodically, it is recommended to use the callback all-data and set the period with set-all-data-period.

tinkerforge call imu-brick <uid> get-imu-temperature
Output:
  • temperature -- int

Returns the temperature of the IMU Brick. The temperature is given in °C/100.

tinkerforge call imu-brick <uid> set-acceleration-range <range>
Parameters:
  • <range> -- int
Output:

no output

Not implemented yet.

tinkerforge call imu-brick <uid> get-acceleration-range
Output:
  • range -- int

Not implemented yet.

tinkerforge call imu-brick <uid> set-magnetometer-range <range>
Parameters:
  • <range> -- int
Output:

no output

Not implemented yet.

tinkerforge call imu-brick <uid> get-magnetometer-range
Output:
  • range -- int

Not implemented yet.

tinkerforge call imu-brick <uid> set-calibration <typ> <data>
Parameters:
  • <typ> -- int (has symbols)
  • <data> -- int,int,int,int,int,int,int,int,int,int
Output:

no output

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 symbols are available for this function:

  • accelerometer-gain = 0, for <typ>
  • accelerometer-bias = 1, for <typ>
  • magnetometer-gain = 2, for <typ>
  • magnetometer-bias = 3, for <typ>
  • gyroscope-gain = 4, for <typ>
  • gyroscope-bias = 5, for <typ>
tinkerforge call imu-brick <uid> get-calibration <typ>
Parameters:
  • <typ> -- int (has symbols)
Output:
  • data -- int,int,int,int,int,int,int,int,int,int

Returns the calibration for a given type as set by set-calibration.

The following symbols are available for this function:

  • accelerometer-gain = 0, for <typ>
  • accelerometer-bias = 1, for <typ>
  • magnetometer-gain = 2, for <typ>
  • magnetometer-bias = 3, for <typ>
  • gyroscope-gain = 4, for <typ>
  • gyroscope-bias = 5, for <typ>
tinkerforge call imu-brick <uid> orientation-calculation-on
Output:no output

Turns the orientation calculation of the IMU Brick on.

As default the calculation is on.

New in version 2.0.2 (Firmware).

tinkerforge call imu-brick <uid> orientation-calculation-off
Output:no output

Turns the orientation calculation of the IMU Brick off.

If the calculation is off, 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).

tinkerforge call imu-brick <uid> is-orientation-calculation-on
Output:
  • orientation-calculation-on -- bool

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

New in version 2.0.2 (Firmware).

tinkerforge call imu-brick <uid> enable-status-led
Output:no output

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).

tinkerforge call imu-brick <uid> disable-status-led
Output:no output

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).

tinkerforge call imu-brick <uid> is-status-led-enabled
Output:
  • enabled -- bool

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

New in version 2.3.1 (Firmware).

tinkerforge call imu-brick <uid> get-protocol1-bricklet-name <port>
Parameters:
  • <port> -- char
Output:
  • protocol-version -- int
  • firmware-version -- int,int,int
  • name -- string

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.

tinkerforge call imu-brick <uid> get-chip-temperature
Output:
  • temperature -- 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.

tinkerforge call imu-brick <uid> reset
Output:no output

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!

tinkerforge call imu-brick <uid> get-identity
Output:
  • uid -- string
  • connected-uid -- string
  • position -- char
  • hardware-version -- int,int,int
  • firmware-version -- int,int,int
  • device-identifier -- int (has symbols)

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

tinkerforge call imu-brick <uid> set-acceleration-period <period>
Parameters:
  • <period> -- int
Output:

no output

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

The default value is 0.

tinkerforge call imu-brick <uid> get-acceleration-period
Output:
  • period -- int

Returns the period as set by set-acceleration-period.

tinkerforge call imu-brick <uid> set-magnetic-field-period <period>
Parameters:
  • <period> -- int
Output:

no output

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

tinkerforge call imu-brick <uid> get-magnetic-field-period
Output:
  • period -- int

Returns the period as set by set-magnetic-field-period.

tinkerforge call imu-brick <uid> set-angular-velocity-period <period>
Parameters:
  • <period> -- int
Output:

no output

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

tinkerforge call imu-brick <uid> get-angular-velocity-period
Output:
  • period -- int

Returns the period as set by set-angular-velocity-period.

tinkerforge call imu-brick <uid> set-all-data-period <period>
Parameters:
  • <period> -- int
Output:

no output

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

tinkerforge call imu-brick <uid> get-all-data-period
Output:
  • period -- int

Returns the period as set by set-all-data-period.

tinkerforge call imu-brick <uid> set-orientation-period <period>
Parameters:
  • <period> -- int
Output:

no output

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

tinkerforge call imu-brick <uid> get-orientation-period
Output:
  • period -- int

Returns the period as set by set-orientation-period.

tinkerforge call imu-brick <uid> set-quaternion-period <period>
Parameters:
  • <period> -- int
Output:

no output

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

tinkerforge call imu-brick <uid> get-quaternion-period
Output:
  • period -- int

Returns the period as set by set-quaternion-period.

Callbacks

Callbacks can be used to receive time critical or recurring data from the device:

tinkerforge dispatch imu-brick <uid> example

The available callbacks 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.

tinkerforge dispatch imu-brick <uid> acceleration
Output:
  • 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.

tinkerforge dispatch imu-brick <uid> magnetic-field
Output:
  • 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.

tinkerforge dispatch imu-brick <uid> angular-velocity
Output:
  • 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.

tinkerforge dispatch imu-brick <uid> all-data
Output:
  • acc-x -- int
  • acc-y -- int
  • acc-z -- int
  • mag-x -- int
  • mag-y -- int
  • mag-z -- int
  • ang-x -- int
  • ang-y -- int
  • ang-z -- int
  • temperature -- int

This callback is triggered periodically with the period that is set by 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.

tinkerforge dispatch imu-brick <uid> orientation
Output:
  • roll -- int
  • pitch -- int
  • yaw -- int

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

tinkerforge dispatch imu-brick <uid> quaternion
Output:
  • x -- float
  • y -- float
  • z -- float
  • w -- float

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.

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