MATLAB/Octave - LCD 20x4 Bricklet¶

Hello World (MATLAB)¶

Download (matlab_example_hello_world.m)

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function matlab_example_hello_world()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletLCD20x4;

    HOST = 'localhost';
    PORT = 4223;
    UID = 'XYZ'; % Change XYZ to the UID of your LCD 20x4 Bricklet

    ipcon = IPConnection(); % Create IP connection
    lcd = handle(BrickletLCD20x4(UID, ipcon), 'CallbackProperties'); % Create device object

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

    % Turn backlight on
    lcd.backlightOn();

    % Write "Hello World"
    lcd.writeLine(0, 0, 'Hello World');

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

Button Callback (MATLAB)¶

Download (matlab_example_button_callback.m)

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function matlab_example_button_callback()
    import com.tinkerforge.IPConnection;
    import com.tinkerforge.BrickletLCD20x4;

    HOST = 'localhost';
    PORT = 4223;
    UID = 'XYZ'; % Change XYZ to the UID of your LCD 20x4 Bricklet

    ipcon = IPConnection(); % Create IP connection
    lcd = handle(BrickletLCD20x4(UID, ipcon), 'CallbackProperties'); % Create device object

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

    % Register button pressed callback to function cb_button_pressed
    set(lcd, 'ButtonPressedCallback', @(h, e) cb_button_pressed(e));

    % Register button released callback to function cb_button_released
    set(lcd, 'ButtonReleasedCallback', @(h, e) cb_button_released(e));

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

% Callback function for button pressed callback
function cb_button_pressed(e)
    fprintf('Button Pressed: %i\n', e.button);
end

% Callback function for button released callback
function cb_button_released(e)
    fprintf('Button Released: %i\n', e.button);
end

Hello World (Octave)¶

Download (octave_example_hello_world.m)

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function octave_example_hello_world()
    more off;

    HOST = "localhost";
    PORT = 4223;
    UID = "XYZ"; % Change XYZ to the UID of your LCD 20x4 Bricklet

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    lcd = javaObject("com.tinkerforge.BrickletLCD20x4", UID, ipcon); % Create device object

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

    % Turn backlight on
    lcd.backlightOn();

    % Write "Hello World"
    lcd.writeLine(0, 0, "Hello World");

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

Button Callback (Octave)¶

Download (octave_example_button_callback.m)

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function octave_example_button_callback()
    more off;

    HOST = "localhost";
    PORT = 4223;
    UID = "XYZ"; % Change XYZ to the UID of your LCD 20x4 Bricklet

    ipcon = javaObject("com.tinkerforge.IPConnection"); % Create IP connection
    lcd = javaObject("com.tinkerforge.BrickletLCD20x4", UID, ipcon); % Create device object

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

    % Register button pressed callback to function cb_button_pressed
    lcd.addButtonPressedCallback(@cb_button_pressed);

    % Register button released callback to function cb_button_released
    lcd.addButtonReleasedCallback(@cb_button_released);

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

% Callback function for button pressed callback
function cb_button_pressed(e)
    fprintf("Button Pressed: %d\n", java2int(e.button));
end

% Callback function for button released callback
function cb_button_released(e)
    fprintf("Button Released: %d\n", java2int(e.button));
end

function int = java2int(value)
    if compare_versions(version(), "3.8", "<=")
        int = value.intValue();
    else
        int = value;
    end
end

Basic Functions¶

class BrickletLCD20x4(String uid, IPConnection ipcon)¶

Parameters:	uid – Type: String ipcon – Type: IPConnection
Returns:	lcd20x4 – Type: BrickletLCD20x4

Creates an object with the unique device ID uid.

In MATLAB:

import com.tinkerforge.BrickletLCD20x4;

lcd20x4 = BrickletLCD20x4('YOUR_DEVICE_UID', ipcon);

In Octave:

lcd20x4 = java_new("com.tinkerforge.BrickletLCD20x4", "YOUR_DEVICE_UID", ipcon);

This object can then be used after the IP Connection is connected.

void BrickletLCD20x4.writeLine(short line, short position, String text)¶

Parameters:	line – Type: short, Range: [0 to 3] position – Type: short, Range: [0 to 19] text – Type: String, Length: up to 20

Writes text to a specific line with a specific position. The text can have a maximum of 20 characters.

For example: (0, 7, "Hello") will write Hello in the middle of the first line of the display.

The display uses a special charset that includes all ASCII characters except backslash and tilde. The LCD charset also includes several other non-ASCII characters, see the charset specification for details. The Unicode example above shows how to specify non-ASCII characters and how to translate from Unicode to the LCD charset.

void BrickletLCD20x4.clearDisplay()¶

Deletes all characters from the display.

void BrickletLCD20x4.backlightOn()¶

Turns the backlight on.

void BrickletLCD20x4.backlightOff()¶

Turns the backlight off.

boolean BrickletLCD20x4.isBacklightOn()¶

Returns:	backlight – Type: boolean

Returns true if the backlight is on and false otherwise.

Advanced Functions¶

void BrickletLCD20x4.setConfig(boolean cursor, boolean blinking)¶

Parameters:	cursor – Type: boolean, Default: false blinking – Type: boolean, Default: false

Configures if the cursor (shown as "_") should be visible and if it should be blinking (shown as a blinking block). The cursor position is one character behind the the last text written with writeLine().

BrickletLCD20x4.Config BrickletLCD20x4.getConfig()¶

Return Object:	cursor – Type: boolean, Default: false blinking – Type: boolean, Default: false

Returns the configuration as set by setConfig().

boolean BrickletLCD20x4.isButtonPressed(short button)¶

Parameters:	button – Type: short, Range: [0 to 3]
Returns:	pressed – Type: boolean

Returns true if the button (0 to 2 or 0 to 3 since hardware version 1.2) is pressed.

If you want to react on button presses and releases it is recommended to use the ButtonPressedCallback and ButtonReleasedCallback callbacks.

void BrickletLCD20x4.setCustomCharacter(short index, short[] character)¶

Parameters:	index – Type: short, Range: [0 to 7] character – Type: short[], Length: 8, Range: [0 to 31]

The LCD 20x4 Bricklet can store up to 8 custom characters. The characters consist of 5x8 pixels and can be addressed with the index 0-7. To describe the pixels, the first 5 bits of 8 bytes are used. For example, to make a custom character "H", you should transfer the following:

• character[0] = 0b00010001 (decimal value 17)
• character[1] = 0b00010001 (decimal value 17)
• character[2] = 0b00010001 (decimal value 17)
• character[3] = 0b00011111 (decimal value 31)
• character[4] = 0b00010001 (decimal value 17)
• character[5] = 0b00010001 (decimal value 17)
• character[6] = 0b00010001 (decimal value 17)
• character[7] = 0b00000000 (decimal value 0)

The characters can later be written with writeLine() by using the characters with the byte representation 8 ("\x08" or "\u0008") to 15 ("\x0F" or "\u000F").

You can play around with the custom characters in Brick Viewer version since 2.0.1.

Custom characters are stored by the LCD in RAM, so they have to be set after each startup.

New in version 2.0.1 (Plugin).

short[] BrickletLCD20x4.getCustomCharacter(short index)¶

Parameters:	index – Type: short, Range: [0 to 7]
Returns:	character – Type: short[], Length: 8, Range: [0 to 31]

Returns the custom character for a given index, as set with setCustomCharacter().

New in version 2.0.1 (Plugin).

void BrickletLCD20x4.setDefaultText(short line, String text)¶

Parameters:	line – Type: short, Range: [0 to 3] text – Type: String, Length: up to 20

Sets the default text for lines 0-3. The max number of characters per line is 20.

The default text is shown on the LCD, if the default text counter expires, see setDefaultTextCounter().

New in version 2.0.2 (Plugin).

String BrickletLCD20x4.getDefaultText(short line)¶

Parameters:	line – Type: short, Range: [0 to 3]
Returns:	text – Type: String, Length: up to 20

Returns the default text for a given line (0-3) as set by setDefaultText().

New in version 2.0.2 (Plugin).

void BrickletLCD20x4.setDefaultTextCounter(int counter)¶

Parameters:	counter – Type: int, Unit: 1 ms, Range: [-231 to 231 - 1], Default: -1

Sets the default text counter. This counter is decremented each ms by the LCD firmware. If the counter reaches 0, the default text (see setDefaultText()) is shown on the LCD.

This functionality can be used to show a default text if the controlling program crashes or the connection is interrupted.

A possible approach is to call setDefaultTextCounter() every minute with the parameter 1000*60*2 (2 minutes). In this case the default text will be shown no later than 2 minutes after the controlling program crashes.

A negative counter turns the default text functionality off.

New in version 2.0.2 (Plugin).

int BrickletLCD20x4.getDefaultTextCounter()¶

Returns:	counter – Type: int, Unit: 1 ms, Range: [-231 to 231 - 1], Default: -1

Returns the current value of the default text counter.

New in version 2.0.2 (Plugin).

BrickletLCD20x4.Identity BrickletLCD20x4.getIdentity()¶

Return Object:

uid – Type: String, Length: up to 8 connectedUid – Type: String, Length: up to 8 position – Type: char, Range: ['a' to 'h', 'z'] hardwareVersion – Type: short[], Length: 3 1: major – Type: short, Range: [0 to 255] 2: minor – Type: short, Range: [0 to 255] 3: revision – Type: short, Range: [0 to 255] firmwareVersion – Type: short[], Length: 3 1: major – Type: short, Range: [0 to 255] 2: minor – Type: short, Range: [0 to 255] 3: revision – Type: short, 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', 'd', 'e', 'f', 'g' or 'h' (Bricklet Port). A Bricklet connected to an Isolator Bricklet is always at position 'z'.

The device identifier numbers can be found here. There is also a constant for the device identifier of this Bricklet.

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.

callback BrickletLCD20x4.ButtonPressedCallback¶

Event Object:	button – Type: short, Range: [0 to 3]

This callback is triggered when a button is pressed. The parameter is the number of the button (0 to 2 or 0 to 3 since hardware version 1.2).

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 addButtonPressedCallback() function. An added callback function can be removed with the removeButtonPressedCallback() function.

callback BrickletLCD20x4.ButtonReleasedCallback¶

Event Object:	button – Type: short, Range: [0 to 3]

This callback is triggered when a button is released. The parameter is the number of the button (0 to 2 or 0 to 3 since hardware version 1.2).

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 addButtonReleasedCallback() function. An added callback function can be removed with the removeButtonReleasedCallback() function.

Virtual Functions¶

Virtual functions don't communicate with the device itself, but operate only on the API bindings device object. They can be called without the corresponding IP Connection object being connected.

short[] BrickletLCD20x4.getAPIVersion()¶

Return Object:	apiVersion – Type: short[], Length: 3 1: major – Type: short, Range: [0 to 255] 2: minor – Type: short, Range: [0 to 255] 3: revision – Type: short, Range: [0 to 255]

Returns the version of the API definition 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 BrickletLCD20x4.getResponseExpected(byte functionId)¶

Parameters:	functionId – Type: byte, 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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For functionId:

• BrickletLCD20x4.FUNCTION_WRITE_LINE = 1
• BrickletLCD20x4.FUNCTION_CLEAR_DISPLAY = 2
• BrickletLCD20x4.FUNCTION_BACKLIGHT_ON = 3
• BrickletLCD20x4.FUNCTION_BACKLIGHT_OFF = 4
• BrickletLCD20x4.FUNCTION_SET_CONFIG = 6
• BrickletLCD20x4.FUNCTION_SET_CUSTOM_CHARACTER = 11
• BrickletLCD20x4.FUNCTION_SET_DEFAULT_TEXT = 13
• BrickletLCD20x4.FUNCTION_SET_DEFAULT_TEXT_COUNTER = 15

void BrickletLCD20x4.setResponseExpected(byte functionId, boolean responseExpected)¶

Parameters:	functionId – Type: byte, 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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For functionId:

• BrickletLCD20x4.FUNCTION_WRITE_LINE = 1
• BrickletLCD20x4.FUNCTION_CLEAR_DISPLAY = 2
• BrickletLCD20x4.FUNCTION_BACKLIGHT_ON = 3
• BrickletLCD20x4.FUNCTION_BACKLIGHT_OFF = 4
• BrickletLCD20x4.FUNCTION_SET_CONFIG = 6
• BrickletLCD20x4.FUNCTION_SET_CUSTOM_CHARACTER = 11
• BrickletLCD20x4.FUNCTION_SET_DEFAULT_TEXT = 13
• BrickletLCD20x4.FUNCTION_SET_DEFAULT_TEXT_COUNTER = 15

void BrickletLCD20x4.setResponseExpectedAll(boolean responseExpected)¶

Parameters:	responseExpected – Type: boolean

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

Constants¶

int BrickletLCD20x4.DEVICE_IDENTIFIER¶

This constant is used to identify a LCD 20x4 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 BrickletLCD20x4.DEVICE_DISPLAY_NAME¶

This constant represents the human readable name of a LCD 20x4 Bricklet.