MATLAB/Octave - Piezo Speaker Bricklet

This is the description of the MATLAB/Octave API bindings for the Piezo Speaker Bricklet. General information and technical specifications for the Piezo Speaker 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).

Beep (MATLAB)

Download (matlab_example_beep.m)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
function matlab_example_beep()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletPiezoSpeaker;

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

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

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

    % Make 2 second beep with a frequency of 1kHz
    ps.beep(2000, 1000);

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

Morse Code (MATLAB)

Download (matlab_example_morse_code.m)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
function matlab_example_morse_code()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletPiezoSpeaker;

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

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

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

    % Morse SOS with a frequency of 2kHz
    ps.morseCode('... --- ...', 2000);

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

Beep (Octave)

Download (octave_example_beep.m)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
function octave_example_beep()
    more off;

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

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

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

    % Make 2 second beep with a frequency of 1kHz
    ps.beep(2000, 1000);

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

Morse Code (Octave)

Download (octave_example_morse_code.m)

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
function octave_example_morse_code()
    more off;

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

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

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

    % Morse SOS with a frequency of 2kHz
    ps.morseCode("... --- ...", 2000);

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

public class BrickletPiezoSpeaker(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletPiezoSpeaker;

piezoSpeaker = BrickletPiezoSpeaker('YOUR_DEVICE_UID', ipcon);

In Octave:

piezoSpeaker = java_new("com.tinkerforge.BrickletPiezoSpeaker", "YOUR_DEVICE_UID", ipcon);

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

public void beep(long duration, int frequency)

Beeps with the given frequency for the duration in ms. For example: If you set a duration of 1000, with a frequency value of 2000 the piezo buzzer will beep for one second with a frequency of approximately 2 kHz.

Changed in version 2.0.2 (Plugin): A duration of 0 stops the current beep if any, the frequency parameter is ignored. A duration of 4294967295 results in an infinite beep.

The frequency parameter can be set between 585 and 7100.

The Piezo Speaker Bricklet can only approximate the frequency, it will play the best possible match by applying the calibration (see calibrate()).

The following constants are available for this function:

  • BrickletPiezoSpeaker.BEEP_DURATION_OFF = 0
  • BrickletPiezoSpeaker.BEEP_DURATION_INFINITE = 4294967295
public void morseCode(String morse, int frequency)

Sets morse code that will be played by the piezo buzzer. The morse code is given as a string consisting of "." (dot), "-" (minus) and " " (space) for dits, dahs and pauses. Every other character is ignored. The second parameter is the frequency (see beep()).

For example: If you set the string "...---...", the piezo buzzer will beep nine times with the durations "short short short long long long short short short".

The maximum string size is 60.

Advanced Functions

public boolean calibrate()

The Piezo Speaker Bricklet can play 512 different tones. This function plays each tone and measures the exact frequency back. The result is a mapping between setting value and frequency. This mapping is stored in the EEPROM and loaded on startup.

The Bricklet should come calibrated, you only need to call this function (once) every time you reflash the Bricklet plugin.

Returns true after the calibration finishes.

public short[] getAPIVersion()

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.

public boolean getResponseExpected(short functionId)

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.

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

public void setResponseExpected(short functionId, boolean responseExpected)

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 function ID constants are available for this function:

  • BrickletPiezoSpeaker.FUNCTION_BEEP = 1
  • BrickletPiezoSpeaker.FUNCTION_MORSE_CODE = 2
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletPiezoSpeaker.Identity getIdentity()

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.

The returned object has the public member variables String uid, String connectedUid, char position, short[] hardwareVersion, short[] firmwareVersion and int deviceIdentifier.

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.

public callback BrickletPiezoSpeaker.BeepFinishedCallback

This callback is triggered if a beep set by beep() is finished

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 addBeepFinishedCallback() function. An added callback function can be removed with the removeBeepFinishedCallback() function.

public callback BrickletPiezoSpeaker.MorseCodeFinishedCallback

This callback is triggered if the playback of the morse code set by morseCode() is finished.

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 addMorseCodeFinishedCallback() function. An added callback function can be removed with the removeMorseCodeFinishedCallback() function.

Constants

public static final int BrickletPiezoSpeaker.DEVICE_IDENTIFIER

This constant is used to identify a Piezo Speaker Bricklet.

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

public static final String BrickletPiezoSpeaker.DEVICE_DISPLAY_NAME

This constant represents the human readable name of a Piezo Speaker Bricklet.