MATLAB/Octave - Compass Bricklet

This is the description of the MATLAB/Octave 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 MATLAB/Octave API bindings is part of their general description.

Examples

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

Simple (MATLAB)

Download (matlab_example_simple.m)

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function matlab_example_simple()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletCompass;

    HOST = 'localhost';
    PORT = 4223;
    UID = 'XYZ'; % Change XYZ to the UID of your Compass Bricklet

    ipcon = IPConnection(); % Create IP connection
    c = handle(BrickletCompass(UID, ipcon), 'CallbackProperties'); % Create device object

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

    % Get current heading
    heading = c.getHeading();
    fprintf('Heading: %g °\n', heading/10.0);

    input('Press key to exit\n', 's');
    ipcon.disconnect();
end

Callback (MATLAB)

Download (matlab_example_callback.m)

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function matlab_example_callback()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletCompass;

    HOST = 'localhost';
    PORT = 4223;
    UID = 'XYZ'; % Change XYZ to the UID of your Compass Bricklet

    ipcon = IPConnection(); % Create IP connection
    c = handle(BrickletCompass(UID, ipcon), 'CallbackProperties'); % Create device object

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

    % Register heading callback to function cb_heading
    set(c, 'HeadingCallback', @(h, e) cb_heading(e));

    % Set period for heading callback to 0.1s (100ms) without a threshold
    c.setHeadingCallbackConfiguration(100, false, 'x', 0, 0);

    input('Press key to exit\n', 's');
    ipcon.disconnect();
end

% Callback function for heading callback
function cb_heading(e)
    fprintf('Heading: %g °\n', e.heading/10.0);
end

Simple (Octave)

Download (octave_example_simple.m)

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function octave_example_simple()
    more off;

    HOST = "localhost";
    PORT = 4223;
    UID = "XYZ"; % Change XYZ to the UID of your Compass Bricklet

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    c = javaObject("com.tinkerforge.BrickletCompass", UID, ipcon); % Create device object

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

    % Get current heading
    heading = c.getHeading();
    fprintf("Heading: %g °\n", heading/10.0);

    input("Press key to exit\n", "s");
    ipcon.disconnect();
end

Callback (Octave)

Download (octave_example_callback.m)

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function octave_example_callback()
    more off;

    HOST = "localhost";
    PORT = 4223;
    UID = "XYZ"; % Change XYZ to the UID of your Compass Bricklet

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    c = javaObject("com.tinkerforge.BrickletCompass", UID, ipcon); % Create device object

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

    % Register heading callback to function cb_heading
    c.addHeadingCallback(@cb_heading);

    % Set period for heading callback to 0.1s (100ms) without a threshold
    c.setHeadingCallbackConfiguration(100, false, "x", 0, 0);

    input("Press key to exit\n", "s");
    ipcon.disconnect();
end

% Callback function for heading callback
function cb_heading(e)
    fprintf("Heading: %g °\n", e.heading/10.0);
end

API

Generally, every method of the MATLAB bindings that returns a value can throw a TimeoutException. This exception gets thrown if the device did not respond. If a cable based connection is used, it is unlikely that this exception gets thrown (assuming nobody unplugs the device). However, if a wireless connection is used, timeouts will occur if the distance to the device gets too big.

Beside the TimeoutException there is also a NotConnectedException that is thrown if a method needs to communicate with the device while the IP Connection is not connected.

Since the MATLAB bindings are based on Java and Java does not support multiple return values and return by reference is not possible for primitive types, we use small classes that only consist of member variables. The member variables of the returned objects are described in the corresponding method descriptions.

The package for all Brick/Bricklet bindings and the IP Connection is com.tinkerforge.*

All methods listed below are thread-safe.

Basic Functions

class BrickletCompass(String uid, IPConnection ipcon)
Parameters:
  • uid – Type: String
  • ipcon – Type: IPConnection
Returns:
  • compass – Type: BrickletCompass

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletCompass;

compass = BrickletCompass('YOUR_DEVICE_UID', ipcon);

In Octave:

compass = java_new("com.tinkerforge.BrickletCompass", "YOUR_DEVICE_UID", ipcon);

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

int BrickletCompass.getHeading()
Returns:
  • 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 getMagneticFluxDensity() 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 HeadingCallback callback. You can set the callback configuration with setHeadingCallbackConfiguration().

BrickletCompass.MagneticFluxDensity BrickletCompass.getMagneticFluxDensity()
Return Object:
  • 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 MagneticFluxDensityCallback callback. You can set the callback configuration with setMagneticFluxDensityCallbackConfiguration().

void BrickletCompass.setConfiguration(int dataRate, boolean backgroundCalibration)
Parameters:
  • dataRate – Type: int, Range: See constants
  • backgroundCalibration – Type: boolean

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 constants are available for this function:

For dataRate:

  • BrickletCompass.DATA_RATE_100HZ = 0
  • BrickletCompass.DATA_RATE_200HZ = 1
  • BrickletCompass.DATA_RATE_400HZ = 2
  • BrickletCompass.DATA_RATE_600HZ = 3
BrickletCompass.Configuration BrickletCompass.getConfiguration()
Return Object:
  • dataRate – Type: int, Range: See constants
  • backgroundCalibration – Type: boolean

Returns the configuration as set by setConfiguration().

The following constants are available for this function:

For dataRate:

  • BrickletCompass.DATA_RATE_100HZ = 0
  • BrickletCompass.DATA_RATE_200HZ = 1
  • BrickletCompass.DATA_RATE_400HZ = 2
  • BrickletCompass.DATA_RATE_600HZ = 3

Advanced Functions

void BrickletCompass.setCalibration(int[] offset, int[] gain)
Parameters:
  • offset – Type: int[], Length: 3, Range: [-215 to 215 - 1]
  • gain – Type: int[], Length: 3, Range: [-215 to 215 - 1]

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.

BrickletCompass.Calibration BrickletCompass.getCalibration()
Return Object:
  • offset – Type: int[], Length: 3, Range: [-215 to 215 - 1]
  • gain – Type: int[], Length: 3, Range: [-215 to 215 - 1]

Returns the calibration parameters as set by setCalibration().

int[] BrickletCompass.getAPIVersion()
Returns:
  • apiVersion – Type: int[], Length: 3, Range: [0 to 255]

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.

boolean BrickletCompass.getResponseExpected(int functionId)
Parameters:
  • functionId – Type: int, Range: See constants
Returns:
  • responseExpected – Type: boolean

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 setResponseExpected(). 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.

The following constants are available for this function:

For functionId:

  • BrickletCompass.FUNCTION_SET_HEADING_CALLBACK_CONFIGURATION = 2
  • BrickletCompass.FUNCTION_SET_MAGNETIC_FLUX_DENSITY_CALLBACK_CONFIGURATION = 6
  • BrickletCompass.FUNCTION_SET_CONFIGURATION = 9
  • BrickletCompass.FUNCTION_SET_CALIBRATION = 11
  • BrickletCompass.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletCompass.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletCompass.FUNCTION_RESET = 243
  • BrickletCompass.FUNCTION_WRITE_UID = 248
void BrickletCompass.setResponseExpected(int functionId, boolean responseExpected)
Parameters:
  • functionId – Type: int, Range: See constants
  • responseExpected – Type: boolean

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.

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 constants are available for this function:

For functionId:

  • BrickletCompass.FUNCTION_SET_HEADING_CALLBACK_CONFIGURATION = 2
  • BrickletCompass.FUNCTION_SET_MAGNETIC_FLUX_DENSITY_CALLBACK_CONFIGURATION = 6
  • BrickletCompass.FUNCTION_SET_CONFIGURATION = 9
  • BrickletCompass.FUNCTION_SET_CALIBRATION = 11
  • BrickletCompass.FUNCTION_SET_WRITE_FIRMWARE_POINTER = 237
  • BrickletCompass.FUNCTION_SET_STATUS_LED_CONFIG = 239
  • BrickletCompass.FUNCTION_RESET = 243
  • BrickletCompass.FUNCTION_WRITE_UID = 248
void BrickletCompass.setResponseExpectedAll(boolean responseExpected)
Parameters:
  • responseExpected – Type: boolean

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

BrickletCompass.SPITFPErrorCount BrickletCompass.getSPITFPErrorCount()
Return Object:
  • errorCountAckChecksum – Type: long, Range: [0 to 232 - 1]
  • errorCountMessageChecksum – Type: long, Range: [0 to 232 - 1]
  • errorCountFrame – Type: long, Range: [0 to 232 - 1]
  • errorCountOverflow – Type: long, 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.

int BrickletCompass.setBootloaderMode(int mode)
Parameters:
  • mode – Type: int, Range: See constants
Returns:
  • status – Type: int, Range: See constants

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 constants are available for this function:

For mode:

  • BrickletCompass.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletCompass.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletCompass.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletCompass.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletCompass.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4

For status:

  • BrickletCompass.BOOTLOADER_STATUS_OK = 0
  • BrickletCompass.BOOTLOADER_STATUS_INVALID_MODE = 1
  • BrickletCompass.BOOTLOADER_STATUS_NO_CHANGE = 2
  • BrickletCompass.BOOTLOADER_STATUS_ENTRY_FUNCTION_NOT_PRESENT = 3
  • BrickletCompass.BOOTLOADER_STATUS_DEVICE_IDENTIFIER_INCORRECT = 4
  • BrickletCompass.BOOTLOADER_STATUS_CRC_MISMATCH = 5
int BrickletCompass.getBootloaderMode()
Returns:
  • mode – Type: int, Range: See constants

Returns the current bootloader mode, see setBootloaderMode().

The following constants are available for this function:

For mode:

  • BrickletCompass.BOOTLOADER_MODE_BOOTLOADER = 0
  • BrickletCompass.BOOTLOADER_MODE_FIRMWARE = 1
  • BrickletCompass.BOOTLOADER_MODE_BOOTLOADER_WAIT_FOR_REBOOT = 2
  • BrickletCompass.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_REBOOT = 3
  • BrickletCompass.BOOTLOADER_MODE_FIRMWARE_WAIT_FOR_ERASE_AND_REBOOT = 4
void BrickletCompass.setWriteFirmwarePointer(long pointer)
Parameters:
  • pointer – Type: long, Range: [0 to 232 - 1]

Sets the firmware pointer for writeFirmware(). 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.

int BrickletCompass.writeFirmware(int[] data)
Parameters:
  • data – Type: int[], Length: 64, Range: [0 to 255]
Returns:
  • status – Type: int, Range: [0 to 255]

Writes 64 Bytes of firmware at the position as written by setWriteFirmwarePointer() 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.

void BrickletCompass.setStatusLEDConfig(int config)
Parameters:
  • config – Type: int, Range: See constants

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 constants are available for this function:

For config:

  • BrickletCompass.STATUS_LED_CONFIG_OFF = 0
  • BrickletCompass.STATUS_LED_CONFIG_ON = 1
  • BrickletCompass.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletCompass.STATUS_LED_CONFIG_SHOW_STATUS = 3
int BrickletCompass.getStatusLEDConfig()
Returns:
  • config – Type: int, Range: See constants

Returns the configuration as set by setStatusLEDConfig()

The following constants are available for this function:

For config:

  • BrickletCompass.STATUS_LED_CONFIG_OFF = 0
  • BrickletCompass.STATUS_LED_CONFIG_ON = 1
  • BrickletCompass.STATUS_LED_CONFIG_SHOW_HEARTBEAT = 2
  • BrickletCompass.STATUS_LED_CONFIG_SHOW_STATUS = 3
int BrickletCompass.getChipTemperature()
Returns:
  • 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.

void BrickletCompass.reset()

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!

void BrickletCompass.writeUID(long uid)
Parameters:
  • uid – Type: long, Range: [0 to 232 - 1]

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.

long BrickletCompass.readUID()
Returns:
  • uid – Type: long, Range: [0 to 232 - 1]

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

BrickletCompass.Identity BrickletCompass.getIdentity()
Return Object:
  • uid – Type: String, Length: up to 8
  • connectedUid – Type: String, Length: up to 8
  • position – Type: char
  • hardwareVersion – Type: int[], Length: 3, Range: [0 to 255]
  • firmwareVersion – Type: int[], Length: 3, Range: [0 to 255]
  • deviceIdentifier – 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. There is also a constant for the device identifier of this Bricklet.

Callback Configuration Functions

void BrickletCompass.setHeadingCallbackConfiguration(long period, boolean valueHasToChange, char option, int min, int max)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • valueHasToChange – Type: boolean, Default: false
  • option – Type: char, Range: See constants, Default: 'x'
  • min – Type: int, Range: [-215 to 215 - 1]
  • max – Type: int, Range: [-215 to 215 - 1]

The period is the period with which the HeadingCallback 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 HeadingCallback 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 constants are available for this function:

For option:

  • BrickletCompass.THRESHOLD_OPTION_OFF = 'x'
  • BrickletCompass.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletCompass.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletCompass.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletCompass.THRESHOLD_OPTION_GREATER = '>'
BrickletCompass.HeadingCallbackConfiguration BrickletCompass.getHeadingCallbackConfiguration()
Return Object:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • valueHasToChange – Type: boolean, Default: false
  • option – Type: char, Range: See constants, 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 setHeadingCallbackConfiguration().

The following constants are available for this function:

For option:

  • BrickletCompass.THRESHOLD_OPTION_OFF = 'x'
  • BrickletCompass.THRESHOLD_OPTION_OUTSIDE = 'o'
  • BrickletCompass.THRESHOLD_OPTION_INSIDE = 'i'
  • BrickletCompass.THRESHOLD_OPTION_SMALLER = '<'
  • BrickletCompass.THRESHOLD_OPTION_GREATER = '>'
void BrickletCompass.setMagneticFluxDensityCallbackConfiguration(long period, boolean valueHasToChange)
Parameters:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • valueHasToChange – Type: boolean, Default: false

The period is the period with which the MagneticFluxDensityCallback 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.

BrickletCompass.MagneticFluxDensityCallbackConfiguration BrickletCompass.getMagneticFluxDensityCallbackConfiguration()
Return Object:
  • period – Type: long, Unit: 1 ms, Range: [0 to 232 - 1], Default: 0
  • valueHasToChange – Type: boolean, Default: false

Returns the callback configuration as set by setMagneticFluxDensityCallbackConfiguration().

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with "set" function of MATLAB. The parameters consist of the IP Connection object, the callback name and the callback function. For example, it looks like this in MATLAB:

function my_callback(e)
    fprintf('Parameter: %s\n', e.param);
end

set(device, 'ExampleCallback', @(h, e) my_callback(e));

Due to a difference in the Octave Java support the "set" function cannot be used in Octave. The registration is done with "add*Callback" functions of the device object. It looks like this in Octave:

function my_callback(e)
    fprintf("Parameter: %s\n", e.param);
end

device.addExampleCallback(@my_callback);

It is possible to add several callbacks and to remove them with the corresponding "remove*Callback" function.

The parameters of the callback are passed to the callback function as fields of the structure e, which is derived from the java.util.EventObject class. The available callback names with corresponding structure fields 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.

callback BrickletCompass.HeadingCallback
Event Object:
  • heading – Type: int, Range: [-215 to 215 - 1]

This callback is triggered periodically according to the configuration set by setHeadingCallbackConfiguration().

The parameter is the same as getHeading().

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addHeadingCallback() function. An added callback function can be removed with the removeHeadingCallback() function.

callback BrickletCompass.MagneticFluxDensityCallback
Event Object:
  • 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 setMagneticFluxDensityCallbackConfiguration().

The parameters are the same as getMagneticFluxDensity().

In MATLAB the set() function can be used to register a callback function to this callback.

In Octave a callback function can be added to this callback using the addMagneticFluxDensityCallback() function. An added callback function can be removed with the removeMagneticFluxDensityCallback() function.

Constants

int BrickletCompass.DEVICE_IDENTIFIER

This constant is used to identify a Compass Bricklet.

The getIdentity() function and the IPConnection.EnumerateCallback callback of the IP Connection have a deviceIdentifier parameter to specify the Brick's or Bricklet's type.

String BrickletCompass.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Compass Bricklet.