Java - LCD 20x4 Bricklet

This is the description of the Java API bindings for the LCD 20x4 Bricklet. General information and technical specifications for the LCD 20x4 Bricklet are summarized in its hardware description.

An installation guide for the Java API bindings is part of their general description.

Examples

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

Hello World

Download (ExampleHelloWorld.java)

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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletLCD20x4;

public class ExampleHelloWorld {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your LCD 20x4 Bricklet
    private static final String UID = "XYZ";

    // Note: To make the example code cleaner we do not handle exceptions. Exceptions
    //       you might normally want to catch are described in the documentation
    public static void main(String args[]) throws Exception {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletLCD20x4 lcd = new 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((short)0, (short)0, "Hello World");

        System.out.println("Press key to exit"); System.in.read();
        ipcon.disconnect();
    }
}

Button Callback

Download (ExampleButtonCallback.java)

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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletLCD20x4;

public class ExampleButtonCallback {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your LCD 20x4 Bricklet
    private static final String UID = "XYZ";

    // Note: To make the example code cleaner we do not handle exceptions. Exceptions
    //       you might normally want to catch are described in the documentation
    public static void main(String args[]) throws Exception {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletLCD20x4 lcd = new BrickletLCD20x4(UID, ipcon); // Create device object

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

        // Add button pressed listener
        lcd.addButtonPressedListener(new BrickletLCD20x4.ButtonPressedListener() {
            public void buttonPressed(short button) {
                System.out.println("Button Pressed: " + button);
            }
        });

        // Add button released listener
        lcd.addButtonReleasedListener(new BrickletLCD20x4.ButtonReleasedListener() {
            public void buttonReleased(short button) {
                System.out.println("Button Released: " + button);
            }
        });

        System.out.println("Press key to exit"); System.in.read();
        ipcon.disconnect();
    }
}

Unicode

Download (ExampleUnicode.java)

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import com.tinkerforge.IPConnection;
import com.tinkerforge.BrickletLCD20x4;

public class ExampleUnicode {
    private static final String HOST = "localhost";
    private static final int PORT = 4223;

    // Change XYZ to the UID of your LCD 20x4 Bricklet
    private static final String UID = "XYZ";

    // Maps a normal UTF-16 encoded string to the LCD charset
    static String utf16ToKS0066U(String utf16)
    {
        String ks0066u = "";
        char c;

        for (int i = 0; i < utf16.length(); i++) {
            int codePoint = utf16.codePointAt(i);

            if (Character.isHighSurrogate(utf16.charAt(i))) {
                // Skip low surrogate
                i++;
            }

            // ASCII subset from JIS X 0201
            if (codePoint >= 0x0020 && codePoint <= 0x007e) {
                // The LCD charset doesn't include '\' and '~', use similar characters instead
                switch (codePoint) {
                case 0x005c: c = (char)0xa4; break; // REVERSE SOLIDUS maps to IDEOGRAPHIC COMMA
                case 0x007e: c = (char)0x2d; break; // TILDE maps to HYPHEN-MINUS
                default: c = (char)codePoint; break;
                }
            }
            // Katakana subset from JIS X 0201
            else if (codePoint >= 0xff61 && codePoint <= 0xff9f) {
                c = (char)(codePoint - 0xfec0);
            }
            // Special characters
            else {
                switch (codePoint) {
                case 0x00a5: c = (char)0x5c; break; // YEN SIGN
                case 0x2192: c = (char)0x7e; break; // RIGHTWARDS ARROW
                case 0x2190: c = (char)0x7f; break; // LEFTWARDS ARROW
                case 0x00b0: c = (char)0xdf; break; // DEGREE SIGN maps to KATAKANA SEMI-VOICED SOUND MARK
                case 0x03b1: c = (char)0xe0; break; // GREEK SMALL LETTER ALPHA
                case 0x00c4: c = (char)0xe1; break; // LATIN CAPITAL LETTER A WITH DIAERESIS
                case 0x00e4: c = (char)0xe1; break; // LATIN SMALL LETTER A WITH DIAERESIS
                case 0x00df: c = (char)0xe2; break; // LATIN SMALL LETTER SHARP S
                case 0x03b5: c = (char)0xe3; break; // GREEK SMALL LETTER EPSILON
                case 0x00b5: c = (char)0xe4; break; // MICRO SIGN
                case 0x03bc: c = (char)0xe4; break; // GREEK SMALL LETTER MU
                case 0x03c2: c = (char)0xe5; break; // GREEK SMALL LETTER FINAL SIGMA
                case 0x03c1: c = (char)0xe6; break; // GREEK SMALL LETTER RHO
                case 0x221a: c = (char)0xe8; break; // SQUARE ROOT
                case 0x00b9: c = (char)0xe9; break; // SUPERSCRIPT ONE maps to SUPERSCRIPT (minus) ONE
                case 0x00a4: c = (char)0xeb; break; // CURRENCY SIGN
                case 0x00a2: c = (char)0xec; break; // CENT SIGN
                case 0x2c60: c = (char)0xed; break; // LATIN CAPITAL LETTER L WITH DOUBLE BAR
                case 0x00f1: c = (char)0xee; break; // LATIN SMALL LETTER N WITH TILDE
                case 0x00d6: c = (char)0xef; break; // LATIN CAPITAL LETTER O WITH DIAERESIS
                case 0x00f6: c = (char)0xef; break; // LATIN SMALL LETTER O WITH DIAERESIS
                case 0x03f4: c = (char)0xf2; break; // GREEK CAPITAL THETA SYMBOL
                case 0x221e: c = (char)0xf3; break; // INFINITY
                case 0x03a9: c = (char)0xf4; break; // GREEK CAPITAL LETTER OMEGA
                case 0x00dc: c = (char)0xf5; break; // LATIN CAPITAL LETTER U WITH DIAERESIS
                case 0x00fc: c = (char)0xf5; break; // LATIN SMALL LETTER U WITH DIAERESIS
                case 0x03a3: c = (char)0xf6; break; // GREEK CAPITAL LETTER SIGMA
                case 0x03c0: c = (char)0xf7; break; // GREEK SMALL LETTER PI
                case 0x0304: c = (char)0xf8; break; // COMBINING MACRON
                case 0x00f7: c = (char)0xfd; break; // DIVISION SIGN

                default:
                case 0x25a0: c = (char)0xff; break; // BLACK SQUARE
                }
            }

            // Special handling for 'x' followed by COMBINING MACRON
            if (c == (char)0xf8) {
                if (!ks0066u.endsWith("x")) {
                    c = (char)0xff; // BLACK SQUARE
                }

                if (ks0066u.length() > 0) {
                    ks0066u = ks0066u.substring(0, ks0066u.length() - 1);
                }
            }

            ks0066u += c;
        }

        return ks0066u;
    }

    // Note: To make the example code cleaner we do not handle exceptions. Exceptions
    //       you might normally want to catch are described in the documentation
    public static void main(String args[]) throws Exception {
        IPConnection ipcon = new IPConnection(); // Create IP connection
        BrickletLCD20x4 lcd = new 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 some strings using the utf16ToKS0066U function to map to the LCD charset
        lcd.writeLine((short)0, (short)0, utf16ToKS0066U("Stromstärke: 17µA"));
        lcd.writeLine((short)1, (short)0, utf16ToKS0066U("Temperatur:  23°C"));

        // Write a string directly including characters from the LCD charset
        lcd.writeLine((short)2, (short)0, "Drehzahl:   750min\u00e9");

        System.out.println("Press key to exit"); System.in.read();
        ipcon.disconnect();
    }
}

API

Generally, every method of the Java 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 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 BrickletLCD20x4(String uid, IPConnection ipcon)

Creates an object with the unique device ID uid:

BrickletLCD20x4 lcd20x4 = new BrickletLCD20x4("YOUR_DEVICE_UID", ipcon);

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

public void writeLine(short line, short position, String text)

Writes text to a specific line (0 to 3) with a specific position (0 to 19). 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.

public void clearDisplay()

Deletes all characters from the display.

public void backlightOn()

Turns the backlight on.

public void backlightOff()

Turns the backlight off.

public boolean isBacklightOn()

Returns true if the backlight is on and false otherwise.

Advanced Functions

public void setConfig(boolean cursor, boolean blinking)

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().

The default is (false, false).

public BrickletLCD20x4.Config getConfig()

Returns the configuration as set by setConfig().

The returned object has the public member variables boolean cursor and boolean blinking.

public boolean isButtonPressed(short button)

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 ButtonPressedListener and ButtonReleasedListener listeners.

public void setCustomCharacter(short index, short[] character)

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") to 15 ("x0F").

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).

public short[] getCustomCharacter(short index)

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

New in version 2.0.1 (Plugin).

public void setDefaultText(short line, String text)

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).

public String getDefaultText(short line)

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

New in version 2.0.2 (Plugin).

public void setDefaultTextCounter(int counter)

Sets the default text counter in ms. 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.

The default is -1.

New in version 2.0.2 (Plugin).

public int getDefaultTextCounter()

Returns the current value of the default text counter.

New in version 2.0.2 (Plugin).

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 listener 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 listener 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:

  • 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
public void setResponseExpectedAll(boolean responseExpected)

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

public BrickletLCD20x4.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.

Listeners

Listeners can be registered to receive time critical or recurring data from the device. The registration is done with "add*Listener" functions of the device object.

The parameter is a listener class object, for example:

device.addExampleListener(new BrickletLCD20x4.ExampleListener() {
    public void property(int value) {
        System.out.println("Value: " + value);
    }
});

The available listener classes with inherent methods to be overwritten are described below. It is possible to add several listeners and to remove them with the corresponding "remove*Listener" function.

Note

Using listeners 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 class BrickletLCD20x4.ButtonPressedListener()

This listener can be added with the addButtonPressedListener() function. An added listener can be removed with the removeButtonPressedListener() function.

public void buttonPressed(short button)

This listener 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).

public class BrickletLCD20x4.ButtonReleasedListener()

This listener can be added with the addButtonReleasedListener() function. An added listener can be removed with the removeButtonReleasedListener() function.

public void buttonReleased(short button)

This listener 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).

Constants

public static final int BrickletLCD20x4.DEVICE_IDENTIFIER

This constant is used to identify a LCD 20x4 Bricklet.

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

public static final String BrickletLCD20x4.DEVICE_DISPLAY_NAME

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