Shell - Compass Bricklet

This is the description of the Shell API bindings for the Compass Bricklet. General information and technical specifications for the Compass Bricklet 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)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Compass Bricklet

# Get current heading
tinkerforge call compass-bricklet $uid get-heading

Callback

Download (example-callback.sh)

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#!/bin/sh
# Connects to localhost:4223 by default, use --host and --port to change this

uid=XYZ # Change XYZ to the UID of your Compass Bricklet

# Handle incoming heading callbacks
tinkerforge dispatch compass-bricklet $uid heading &

# Set period for heading callback to 0.1s (100ms) without a threshold
tinkerforge call compass-bricklet $uid set-heading-callback-configuration 100 false threshold-option-off 0 0

echo "Press key to exit"; read dummy

kill -- -$$ # Stop callback dispatch in background

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 compass-bricklet [<option>..] <uid> <function> [<argument>..]
Parameters:
  • <uid> – Type: String
  • <function> – Type: String

The call command is used to call a function of the Compass Bricklet. 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 Compass Bricklet and exits
tinkerforge dispatch compass-bricklet [<option>..] <uid> <callback>
Parameters:
  • <uid> – Type: String
  • <callback> – Type: String

The dispatch command is used to dispatch a callback of the Compass Bricklet. 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 Compass Bricklet and exits
tinkerforge call compass-bricklet <uid> <function> [<option>..] [<argument>..]
Parameters:
  • <uid> – Type: String
  • <function> – Type: 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 compass-bricklet <uid> <callback> [<option>..]
Parameters:
  • <uid> – Type: String
  • <callback> – Type: 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 compass-bricklet <uid> get-heading
Output:
  • heading – Type: Int, Range: [-215 to 215 - 1]

Returns the heading in 1/10 degree (north = 0 degree, east = 90 degree).

Alternatively you can use get-magnetic-flux-density and calculate the heading with heading = atan2(y, x) * 180 / PI.

If you want to get the value periodically, it is recommended to use the heading callback. You can set the callback configuration with set-heading-callback-configuration.

tinkerforge call compass-bricklet <uid> get-magnetic-flux-density
Output:
  • x – Type: Int, Range: [-231 to 231 - 1]
  • y – Type: Int, Range: [-231 to 231 - 1]
  • z – Type: Int, Range: [-231 to 231 - 1]

Returns the magnetic flux density (magnetic induction) for all three axis in 1/10 mG (milli Gauss).

If you want to get the value periodically, it is recommended to use the magnetic-flux-density callback. You can set the callback configuration with set-magnetic-flux-density-callback-configuration.

tinkerforge call compass-bricklet <uid> set-configuration <data-rate> <background-calibration>
Parameters:
  • <data-rate> – Type: Int, Range: See symbols
  • <background-calibration> – Type: Bool
Output:
  • no output

Configures the data rate and background calibration.

  • Data Rate: Sets the data rate that is used by the magnetometer. The lower the data rate, the lower is the noise on the data.
  • Background Calibration: Set to true to enable the background calibration and false to turn it off. If the background calibration is enabled the sensing polarity is flipped once per second to automatically calculate and remove offset that is caused by temperature changes. This polarity flipping takes about 20ms. This means that once a second you will not get new data for a period of 20ms. We highly recommend that you keep the background calibration enabled and only disable it if the 20ms off-time is a problem in your application.

Default values: Data rate of 100Hz and background calibration enabled.

The following symbols are available for this function:

For <data-rate>:

  • data-rate-100hz = 0
  • data-rate-200hz = 1
  • data-rate-400hz = 2
  • data-rate-600hz = 3
tinkerforge call compass-bricklet <uid> get-configuration
Output:
  • data-rate – Type: Int, Range: See symbols
  • background-calibration – Type: Bool

Returns the configuration as set by set-configuration.

The following symbols are available for this function:

For data-rate:

  • data-rate-100hz = 0
  • data-rate-200hz = 1
  • data-rate-400hz = 2
  • data-rate-600hz = 3

Advanced Functions

tinkerforge call compass-bricklet <uid> set-calibration <offset> <gain>
Parameters:
  • <offset> – Type: Int Array, Length: 3, Range: [-215 to 215 - 1]
  • <gain> – Type: Int Array, Length: 3, Range: [-215 to 215 - 1]
Output:
  • no output

Sets offset and gain for each of the three axes.

The Bricklet is factory calibrated. If you want to re-calibrate the Bricklet we recommend that you do the calibration through Brick Viewer.

The calibration is saved in non-volatile memory and only has to be done once.

tinkerforge call compass-bricklet <uid> get-calibration
Output:
  • offset – Type: Int Array, Length: 3, Range: [-215 to 215 - 1]
  • gain – Type: Int Array, Length: 3, Range: [-215 to 215 - 1]

Returns the calibration parameters as set by set-calibration.

tinkerforge call compass-bricklet <uid> get-spitfp-error-count
Output:
  • error-count-ack-checksum – Type: Int, Range: [0 to 232 - 1]
  • error-count-message-checksum – Type: Int, Range: [0 to 232 - 1]
  • error-count-frame – Type: Int, Range: [0 to 232 - 1]
  • error-count-overflow – Type: Int, Range: [0 to 232 - 1]

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 Bricklet side. All Bricks have a similar function that returns the errors on the Brick side.

tinkerforge call compass-bricklet <uid> set-bootloader-mode <mode>
Parameters:
  • <mode> – Type: Int, Range: See symbols
Output:
  • status – Type: Int, Range: See symbols

Sets the bootloader mode and returns the status after the requested mode change was instigated.

You can change from bootloader mode to firmware mode and vice versa. A change from bootloader mode to firmware mode will only take place if the entry function, device identifier and CRC are present and correct.

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

The following symbols are available for this function:

For <mode>:

  • bootloader-mode-bootloader = 0
  • bootloader-mode-firmware = 1
  • bootloader-mode-bootloader-wait-for-reboot = 2
  • bootloader-mode-firmware-wait-for-reboot = 3
  • bootloader-mode-firmware-wait-for-erase-and-reboot = 4

For status:

  • bootloader-status-ok = 0
  • bootloader-status-invalid-mode = 1
  • bootloader-status-no-change = 2
  • bootloader-status-entry-function-not-present = 3
  • bootloader-status-device-identifier-incorrect = 4
  • bootloader-status-crc-mismatch = 5
tinkerforge call compass-bricklet <uid> get-bootloader-mode
Output:
  • mode – Type: Int, Range: See symbols

Returns the current bootloader mode, see set-bootloader-mode.

The following symbols are available for this function:

For mode:

  • bootloader-mode-bootloader = 0
  • bootloader-mode-firmware = 1
  • bootloader-mode-bootloader-wait-for-reboot = 2
  • bootloader-mode-firmware-wait-for-reboot = 3
  • bootloader-mode-firmware-wait-for-erase-and-reboot = 4
tinkerforge call compass-bricklet <uid> set-write-firmware-pointer <pointer>
Parameters:
  • <pointer> – Type: Int, Range: [0 to 232 - 1]
Output:
  • no output

Sets the firmware pointer for write-firmware. The pointer has to be increased by chunks of size 64. The data is written to flash every 4 chunks (which equals to one page of size 256).

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

tinkerforge call compass-bricklet <uid> write-firmware <data>
Parameters:
  • <data> – Type: Int Array, Length: 64, Range: [0 to 255]
Output:
  • status – Type: Int, Range: [0 to 255]

Writes 64 Bytes of firmware at the position as written by set-write-firmware-pointer before. The firmware is written to flash every 4 chunks.

You can only write firmware in bootloader mode.

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

tinkerforge call compass-bricklet <uid> set-status-led-config <config>
Parameters:
  • <config> – Type: Int, Range: See symbols
Output:
  • no output

Sets the status LED configuration. By default the LED shows communication traffic between Brick and Bricklet, it flickers once for every 10 received data packets.

You can also turn the LED permanently on/off or show a heartbeat.

If the Bricklet is in bootloader mode, the LED is will show heartbeat by default.

The following symbols are available for this function:

For <config>:

  • status-led-config-off = 0
  • status-led-config-on = 1
  • status-led-config-show-heartbeat = 2
  • status-led-config-show-status = 3
tinkerforge call compass-bricklet <uid> get-status-led-config
Output:
  • config – Type: Int, Range: See symbols

Returns the configuration as set by set-status-led-config

The following symbols are available for this function:

For config:

  • status-led-config-off = 0
  • status-led-config-on = 1
  • status-led-config-show-heartbeat = 2
  • status-led-config-show-status = 3
tinkerforge call compass-bricklet <uid> get-chip-temperature
Output:
  • temperature – Type: Int, Range: [-215 to 215 - 1]

Returns the temperature in °C 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 bad accuracy. Practically it is only useful as an indicator for temperature changes.

tinkerforge call compass-bricklet <uid> reset
Output:
  • no output

Calling this function will reset the Bricklet. All configurations will be lost.

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

tinkerforge call compass-bricklet <uid> write-uid <uid>
Parameters:
  • <uid> – Type: Int, Range: [0 to 232 - 1]
Output:
  • no output

Writes a new UID into flash. If you want to set a new UID you have to decode the Base58 encoded UID string into an integer first.

We recommend that you use Brick Viewer to change the UID.

tinkerforge call compass-bricklet <uid> read-uid
Output:
  • uid – Type: Int, Range: [0 to 232 - 1]

Returns the current UID as an integer. Encode as Base58 to get the usual string version.

tinkerforge call compass-bricklet <uid> get-identity
Output:
  • uid – Type: String, Length: up to 8
  • connected-uid – Type: String, Length: up to 8
  • position – Type: Char
  • hardware-version – Type: Int Array, Length: 3, Range: [0 to 255]
  • firmware-version – Type: Int Array, Length: 3, Range: [0 to 255]
  • device-identifier – Type: Int, Range: [0 to 216 - 1]

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

The position can be 'a', 'b', 'c' or 'd'.

The device identifier numbers can be found here

Callback Configuration Functions

tinkerforge call compass-bricklet <uid> set-heading-callback-configuration <period> <value-has-to-change> <option> <min> <max>
Parameters:
  • <period> – Type: Int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • <value-has-to-change> – Type: Bool, Default: false
  • <option> – Type: Char, Range: See symbols, Default: x
  • <min> – Type: Int, Range: [-215 to 215 - 1]
  • <max> – Type: Int, Range: [-215 to 215 - 1]
Output:
  • no output

The period is the period with which the heading callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

It is furthermore possible to constrain the callback with thresholds.

The option-parameter together with min/max sets a threshold for the heading callback.

The following options are possible:

Option Description
'x' Threshold is turned off
'o' Threshold is triggered when the value is outside the min and max values
'i' Threshold is triggered when the value is inside or equal to the min and max values
'<' Threshold is triggered when the value is smaller than the min value (max is ignored)
'>' Threshold is triggered when the value is greater than the min value (max is ignored)

If the option is set to 'x' (threshold turned off) the callback is triggered with the fixed period.

The default value is (0, false, 'x', 0, 0).

The following symbols are available for this function:

For <option>:

  • threshold-option-off = x
  • threshold-option-outside = o
  • threshold-option-inside = i
  • threshold-option-smaller = <
  • threshold-option-greater = >
tinkerforge call compass-bricklet <uid> get-heading-callback-configuration
Output:
  • period – Type: Int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • value-has-to-change – Type: Bool, Default: false
  • option – Type: Char, Range: See symbols, Default: x
  • min – Type: Int, Range: [-215 to 215 - 1]
  • max – Type: Int, Range: [-215 to 215 - 1]

Returns the callback configuration as set by set-heading-callback-configuration.

The following symbols are available for this function:

For option:

  • threshold-option-off = x
  • threshold-option-outside = o
  • threshold-option-inside = i
  • threshold-option-smaller = <
  • threshold-option-greater = >
tinkerforge call compass-bricklet <uid> set-magnetic-flux-density-callback-configuration <period> <value-has-to-change>
Parameters:
  • <period> – Type: Int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • <value-has-to-change> – Type: Bool, Default: false
Output:
  • no output

The period is the period with which the magnetic-flux-density callback is triggered periodically. A value of 0 turns the callback off.

If the value has to change-parameter is set to true, the callback is only triggered after the value has changed. If the value didn't change within the period, the callback is triggered immediately on change.

If it is set to false, the callback is continuously triggered with the period, independent of the value.

tinkerforge call compass-bricklet <uid> get-magnetic-flux-density-callback-configuration
Output:
  • period – Type: Int, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • value-has-to-change – Type: Bool, Default: false

Returns the callback configuration as set by set-magnetic-flux-density-callback-configuration.

Callbacks

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

tinkerforge dispatch compass-bricklet <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 compass-bricklet <uid> heading
Output:
  • heading – Type: Int, Range: [-215 to 215 - 1]

This callback is triggered periodically according to the configuration set by set-heading-callback-configuration.

The parameter is the same as get-heading.

tinkerforge dispatch compass-bricklet <uid> magnetic-flux-density
Output:
  • x – Type: Int, Range: [-231 to 231 - 1]
  • y – Type: Int, Range: [-231 to 231 - 1]
  • z – Type: Int, Range: [-231 to 231 - 1]

This callback is triggered periodically according to the configuration set by set-magnetic-flux-density-callback-configuration.

The parameters are the same as get-magnetic-flux-density.