JavaScript - LCD 20x4 Bricklet

This is the description of the JavaScript 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 JavaScript API bindings is part of their general description.

Examples

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

Hello World (Node.js)

Download (ExampleHelloWorld.js)

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var Tinkerforge = require('tinkerforge');

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

var ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lcd = new Tinkerforge.BrickletLCD20x4(UID, ipcon); // Create device object

ipcon.connect(HOST, PORT,
    function (error) {
        console.log('Error: ' + error);
    }
); // Connect to brickd
// Don't use device before ipcon is connected

ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
    function (connectReason) {
        // Turn backlight on
        lcd.backlightOn();

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

console.log('Press key to exit');
process.stdin.on('data',
    function (data) {
        ipcon.disconnect();
        process.exit(0);
    }
);

Button Callback (Node.js)

Download (ExampleButtonCallback.js)

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var Tinkerforge = require('tinkerforge');

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

var ipcon = new Tinkerforge.IPConnection(); // Create IP connection
var lcd = new Tinkerforge.BrickletLCD20x4(UID, ipcon); // Create device object

ipcon.connect(HOST, PORT,
    function (error) {
        console.log('Error: ' + error);
    }
); // Connect to brickd
// Don't use device before ipcon is connected

// Register button pressed callback
lcd.on(Tinkerforge.BrickletLCD20x4.CALLBACK_BUTTON_PRESSED,
    // Callback function for button pressed callback
    function (button) {
        console.log('Button Pressed: ' + button);
    }
);

// Register button released callback
lcd.on(Tinkerforge.BrickletLCD20x4.CALLBACK_BUTTON_RELEASED,
    // Callback function for button released callback
    function (button) {
        console.log('Button Released: ' + button);
    }
);

console.log('Press key to exit');
process.stdin.on('data',
    function (data) {
        ipcon.disconnect();
        process.exit(0);
    }
);

Hello World (HTML)

Download (ExampleHelloWorld.html), Test (ExampleHelloWorld.html)

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<!DOCTYPE html>
<html>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <head>
        <title>Tinkerforge | JavaScript Example</title>
    </head>
    <body>
        <div style="text-align:center;">
            <h1>LCD 20x4 Bricklet Hello World Example</h1>
            <p>
                <input value="localhost" id="host" type="text" size="20">:
                <input value="4280" id="port" type="text" size="5">,
                <input value="uid" id="uid" type="text" size="5">
                <input value="Start Example" id="start" type="button" onclick="startExample();">
            </p>
            <p>
                <textarea readonly id="text" cols="80" rows="24" style="resize:none;"
                          >Press "Start Example" to begin ...</textarea>
            </p>
        </div>
        <script src="./Tinkerforge.js" type='text/javascript'></script>
        <script type='text/javascript'>
            var ipcon;
            var textArea = document.getElementById("text");
            function startExample() {
                textArea.value = "";
                var HOST = document.getElementById("host").value;
                var PORT = parseInt(document.getElementById("port").value);
                var UID = document.getElementById("uid").value;
                if(ipcon !== undefined) {
                    ipcon.disconnect();
                }
                ipcon = new Tinkerforge.IPConnection(); // Create IP connection
                var lcd = new Tinkerforge.BrickletLCD20x4(UID, ipcon); // Create device object
                ipcon.connect(HOST, PORT,
                    function(error) {
                        textArea.value += 'Error: ' + error + '\n';
                    }
                ); // Connect to brickd
                // Don't use device before ipcon is connected

                ipcon.on(Tinkerforge.IPConnection.CALLBACK_CONNECTED,
                    function (connectReason) {
                        // Turn backlight on
                        lcd.backlightOn();

                        // Write "Hello World"
                        lcd.writeLine(0, 0, 'Hello World');
                    }
                );
            }
        </script>
    </body>
</html>

Button Callback (HTML)

Download (ExampleButtonCallback.html), Test (ExampleButtonCallback.html)

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<!DOCTYPE html>
<html>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <head>
        <title>Tinkerforge | JavaScript Example</title>
    </head>
    <body>
        <div style="text-align:center;">
            <h1>LCD 20x4 Bricklet Button Callback Example</h1>
            <p>
                <input value="localhost" id="host" type="text" size="20">:
                <input value="4280" id="port" type="text" size="5">,
                <input value="uid" id="uid" type="text" size="5">
                <input value="Start Example" id="start" type="button" onclick="startExample();">
            </p>
            <p>
                <textarea readonly id="text" cols="80" rows="24" style="resize:none;"
                          >Press "Start Example" to begin ...</textarea>
            </p>
        </div>
        <script src="./Tinkerforge.js" type='text/javascript'></script>
        <script type='text/javascript'>
            var ipcon;
            var textArea = document.getElementById("text");
            function startExample() {
                textArea.value = "";
                var HOST = document.getElementById("host").value;
                var PORT = parseInt(document.getElementById("port").value);
                var UID = document.getElementById("uid").value;
                if(ipcon !== undefined) {
                    ipcon.disconnect();
                }
                ipcon = new Tinkerforge.IPConnection(); // Create IP connection
                var lcd = new Tinkerforge.BrickletLCD20x4(UID, ipcon); // Create device object
                ipcon.connect(HOST, PORT,
                    function(error) {
                        textArea.value += 'Error: ' + error + '\n';
                    }
                ); // Connect to brickd
                // Don't use device before ipcon is connected

                // Register button pressed callback
                lcd.on(Tinkerforge.BrickletLCD20x4.CALLBACK_BUTTON_PRESSED,
                    // Callback function for button pressed callback
                    function (button) {
                        textArea.value += 'Button Pressed: ' + button + '\n';
                        textArea.scrollTop = textArea.scrollHeight;
                    }
                );

                // Register button released callback
                lcd.on(Tinkerforge.BrickletLCD20x4.CALLBACK_BUTTON_RELEASED,
                    // Callback function for button released callback
                    function (button) {
                        textArea.value += 'Button Released: ' + button + '\n';
                        textArea.scrollTop = textArea.scrollHeight;
                    }
                );
            }
        </script>
    </body>
</html>

API

Generally, every function of the JavaScript bindings can take two optional parameters, returnCallback and errorCallback. These are two user defined callback functions. The returnCallback function is called with the results as arguments, if the function returns its results asynchronously. The errorCallback is called with an error code in case of an error. The error code can be one of the following values:

  • IPConnection.ERROR_ALREADY_CONNECTED = 11
  • IPConnection.ERROR_NOT_CONNECTED = 12
  • IPConnection.ERROR_CONNECT_FAILED = 13
  • IPConnection.ERROR_INVALID_FUNCTION_ID = 21
  • IPConnection.ERROR_TIMEOUT = 31
  • IPConnection.ERROR_INVALID_PARAMETER = 41
  • IPConnection.ERROR_FUNCTION_NOT_SUPPORTED = 42
  • IPConnection.ERROR_UNKNOWN_ERROR = 43
  • IPConnection.ERROR_STREAM_OUT_OF_SYNC = 51
  • IPConnection.ERROR_NON_ASCII_CHAR_IN_SECRET = 71

The namespace for the JavaScript bindings is Tinkerforge.*.

Basic Functions

new BrickletLCD20x4(uid, ipcon)
Parameters:
  • uid – Type: string
  • ipcon – Type: IPConnection
Returns:
  • lcd20x4 – Type: BrickletLCD20x4

Creates an object with the unique device ID uid:

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

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

BrickletLCD20x4.writeLine(line, position, text[, returnCallback][, errorCallback])
Parameters:
  • line – Type: int, Range: [0 to 3]
  • position – Type: int, Range: [0 to 19]
  • text – Type: string, Length: up to 20
Callback Parameters:
  • undefined
Returns:
  • undefined

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.

BrickletLCD20x4.clearDisplay([returnCallback][, errorCallback])
Callback Parameters:
  • undefined
Returns:
  • undefined

Deletes all characters from the display.

BrickletLCD20x4.backlightOn([returnCallback][, errorCallback])
Callback Parameters:
  • undefined
Returns:
  • undefined

Turns the backlight on.

BrickletLCD20x4.backlightOff([returnCallback][, errorCallback])
Callback Parameters:
  • undefined
Returns:
  • undefined

Turns the backlight off.

BrickletLCD20x4.isBacklightOn([returnCallback][, errorCallback])
Callback Parameters:
  • backlight – Type: boolean
Returns:
  • undefined

Returns true if the backlight is on and false otherwise.

Advanced Functions

BrickletLCD20x4.setConfig(cursor, blinking[, returnCallback][, errorCallback])
Parameters:
  • cursor – Type: boolean, Default: false
  • blinking – Type: boolean, Default: false
Callback Parameters:
  • undefined
Returns:
  • undefined

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.getConfig([returnCallback][, errorCallback])
Callback Parameters:
  • cursor – Type: boolean, Default: false
  • blinking – Type: boolean, Default: false
Returns:
  • undefined

Returns the configuration as set by setConfig().

BrickletLCD20x4.isButtonPressed(button[, returnCallback][, errorCallback])
Parameters:
  • button – Type: int, Range: [0 to 3]
Callback Parameters:
  • pressed – Type: boolean
Returns:
  • undefined

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 CALLBACK_BUTTON_PRESSED and CALLBACK_BUTTON_RELEASED callbacks.

BrickletLCD20x4.setCustomCharacter(index, character[, returnCallback][, errorCallback])
Parameters:
  • index – Type: int, Range: [0 to 7]
  • character – Type: [int, ...], Length: 8, Range: [0 to 31]
Callback Parameters:
  • undefined
Returns:
  • undefined

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).

BrickletLCD20x4.getCustomCharacter(index[, returnCallback][, errorCallback])
Parameters:
  • index – Type: int, Range: [0 to 7]
Callback Parameters:
  • character – Type: [int, ...], Length: 8, Range: [0 to 31]
Returns:
  • undefined

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

New in version 2.0.1 (Plugin).

BrickletLCD20x4.setDefaultText(line, text[, returnCallback][, errorCallback])
Parameters:
  • line – Type: int, Range: [0 to 3]
  • text – Type: string, Length: up to 20
Callback Parameters:
  • undefined
Returns:
  • undefined

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).

BrickletLCD20x4.getDefaultText(line[, returnCallback][, errorCallback])
Parameters:
  • line – Type: int, Range: [0 to 3]
Callback Parameters:
  • text – Type: string, Length: up to 20
Returns:
  • undefined

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

New in version 2.0.2 (Plugin).

BrickletLCD20x4.setDefaultTextCounter(counter[, returnCallback][, errorCallback])
Parameters:
  • counter – Type: int, Unit: 1 ms, Range: [-231 to 231 - 1], Default: -1
Callback Parameters:
  • undefined
Returns:
  • undefined

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).

BrickletLCD20x4.getDefaultTextCounter([returnCallback][, errorCallback])
Callback Parameters:
  • counter – Type: int, Unit: 1 ms, Range: [-231 to 231 - 1], Default: -1
Returns:
  • undefined

Returns the current value of the default text counter.

New in version 2.0.2 (Plugin).

BrickletLCD20x4.getIdentity([returnCallback][, errorCallback])
Callback Parameters:
  • uid – Type: string, Length: up to 8
  • connectedUid – Type: string, Length: up to 8
  • position – Type: char, Range: ['a' to 'h', 'i', 'z']
  • hardwareVersion – Type: [int, ...], Length: 3
    • 0: major – Type: int, Range: [0 to 255]
    • 1: minor – Type: int, Range: [0 to 255]
    • 2: revision – Type: int, Range: [0 to 255]
  • firmwareVersion – Type: [int, ...], Length: 3
    • 0: major – Type: int, Range: [0 to 255]
    • 1: minor – Type: int, Range: [0 to 255]
    • 2: revision – Type: int, Range: [0 to 255]
  • deviceIdentifier – Type: int, Range: [0 to 216 - 1]
Returns:
  • undefined

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). The Raspberry Pi HAT (Zero) Brick is always at position 'i' and the Bricklet connected to an Isolator Bricklet is always as position 'z'.

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

Callback Configuration Functions

BrickletLCD20x4.on(callback_id, function)
Parameters:
  • callback_id – Type: int
  • function – Type: function
Returns:
  • undefined

Registers the given function with the given callback_id.

The available callback IDs with corresponding function signatures are listed below.

Callbacks

Callbacks can be registered to receive time critical or recurring data from the device. The registration is done with the on() function of the device object. The first parameter is the callback ID and the second parameter the callback function:

lcd20x4.on(BrickletLCD20x4.CALLBACK_EXAMPLE,
    function (param) {
        console.log(param);
    }
);

The available constants with inherent number and type of parameters 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.

BrickletLCD20x4.CALLBACK_BUTTON_PRESSED
Callback Parameters:
  • button – Type: int, 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).

BrickletLCD20x4.CALLBACK_BUTTON_RELEASED
Callback Parameters:
  • button – Type: int, 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).

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.

BrickletLCD20x4.getAPIVersion()
Returns:
  • apiVersion – Type: [int, ...], Length: 3
    • 0: major – Type: int, Range: [0 to 255]
    • 1: minor – Type: int, Range: [0 to 255]
    • 2: revision – Type: int, 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.

BrickletLCD20x4.getResponseExpected(functionId[, errorCallback])
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 function_id:

  • 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
BrickletLCD20x4.setResponseExpected(functionId, responseExpected[, errorCallback])
Parameters:
  • functionId – Type: int, Range: See constants
  • responseExpected – Type: boolean
Returns:
  • undefined

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 function_id:

  • 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
BrickletLCD20x4.setResponseExpectedAll(responseExpected)
Parameters:
  • responseExpected – Type: boolean
Returns:
  • undefined

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

Constants

BrickletLCD20x4.DEVICE_IDENTIFIER

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

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

BrickletLCD20x4.DEVICE_DISPLAY_NAME

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