PHP - LCD 20x4 Bricklet

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

Examples

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

Hello World

Download (ExampleHelloWorld.php)

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<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletLCD20x4.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLCD20x4;

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

$ipcon = new IPConnection(); // Create IP connection
$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(0, 0, 'Hello World');

echo "Press key to exit\n";
fgetc(fopen('php://stdin', 'r'));
$ipcon->disconnect();

?>

Button Callback

Download (ExampleButtonCallback.php)

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<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletLCD20x4.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLCD20x4;

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

// Callback function for button pressed callback
function cb_buttonPressed($button)
{
    echo "Button Pressed: $button\n";
}

// Callback function for button released callback
function cb_buttonReleased($button)
{
    echo "Button Released: $button\n";
}

$ipcon = new IPConnection(); // Create IP connection
$lcd = new 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_buttonPressed
$lcd->registerCallback(BrickletLCD20x4::CALLBACK_BUTTON_PRESSED, 'cb_buttonPressed');

// Register button released callback to function cb_buttonReleased
$lcd->registerCallback(BrickletLCD20x4::CALLBACK_BUTTON_RELEASED, 'cb_buttonReleased');

echo "Press ctrl+c to exit\n";
$ipcon->dispatchCallbacks(-1); // Dispatch callbacks forever

?>

Unicode

Download (ExampleUnicode.php)

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<?php

require_once('Tinkerforge/IPConnection.php');
require_once('Tinkerforge/BrickletLCD20x4.php');

use Tinkerforge\IPConnection;
use Tinkerforge\BrickletLCD20x4;

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

// Maps a string to the LCD charset
function autoToKS0066U($string)
{
    $ks0066u = '';
    $utf32le = mb_convert_encoding($string, 'UTF-32LE', 'auto');
    $c = '';

    for ($i = 0; $i < strlen($utf32le); $i += 4) {
        // Combine 4 bytes into 1 code point
        $codePoint = ord($utf32le[$i]) + ord($utf32le[$i + 1]) * 256 + 
                     ord($utf32le[$i + 2]) * 65536 + ord($utf32le[$i + 3]) * 16777216;

        // 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 = chr(0xa4); break; // REVERSE SOLIDUS maps to IDEOGRAPHIC COMMA
            case 0x007e: $c = chr(0x2d); break; // TILDE maps to HYPHEN-MINUS
            default: $c = chr($codePoint); break;
            }
        }
        // Katakana subset from JIS X 0201
        else if ($codePoint >= 0xff61 && $codePoint <= 0xff9f) {
            $c = chr($codePoint - 0xfec0);
        }
        // Special characters
        else {
            switch ($codePoint) {
            case 0x00a5: $c = chr(0x5c); break; // YEN SIGN
            case 0x2192: $c = chr(0x7e); break; // RIGHTWARDS ARROW
            case 0x2190: $c = chr(0x7f); break; // LEFTWARDS ARROW
            case 0x00b0: $c = chr(0xdf); break; // DEGREE SIGN maps to KATAKANA SEMI-VOICED SOUND MARK
            case 0x03b1: $c = chr(0xe0); break; // GREEK SMALL LETTER ALPHA
            case 0x00c4: $c = chr(0xe1); break; // LATIN CAPITAL LETTER A WITH DIAERESIS
            case 0x00e4: $c = chr(0xe1); break; // LATIN SMALL LETTER A WITH DIAERESIS
            case 0x00df: $c = chr(0xe2); break; // LATIN SMALL LETTER SHARP S
            case 0x03b5: $c = chr(0xe3); break; // GREEK SMALL LETTER EPSILON
            case 0x00b5: $c = chr(0xe4); break; // MICRO SIGN
            case 0x03bc: $c = chr(0xe4); break; // GREEK SMALL LETTER MU
            case 0x03c2: $c = chr(0xe5); break; // GREEK SMALL LETTER FINAL SIGMA
            case 0x03c1: $c = chr(0xe6); break; // GREEK SMALL LETTER RHO
            case 0x221a: $c = chr(0xe8); break; // SQUARE ROOT
            case 0x00b9: $c = chr(0xe9); break; // SUPERSCRIPT ONE maps to SUPERSCRIPT (minus) ONE
            case 0x00a4: $c = chr(0xeb); break; // CURRENCY SIGN
            case 0x00a2: $c = chr(0xec); break; // CENT SIGN
            case 0x2c60: $c = chr(0xed); break; // LATIN CAPITAL LETTER L WITH DOUBLE BAR
            case 0x00f1: $c = chr(0xee); break; // LATIN SMALL LETTER N WITH TILDE
            case 0x00d6: $c = chr(0xef); break; // LATIN CAPITAL LETTER O WITH DIAERESIS
            case 0x00f6: $c = chr(0xef); break; // LATIN SMALL LETTER O WITH DIAERESIS
            case 0x03f4: $c = chr(0xf2); break; // GREEK CAPITAL THETA SYMBOL
            case 0x221e: $c = chr(0xf3); break; // INFINITY
            case 0x03a9: $c = chr(0xf4); break; // GREEK CAPITAL LETTER OMEGA
            case 0x00dc: $c = chr(0xf5); break; // LATIN CAPITAL LETTER U WITH DIAERESIS
            case 0x00fc: $c = chr(0xf5); break; // LATIN SMALL LETTER U WITH DIAERESIS
            case 0x03a3: $c = chr(0xf6); break; // GREEK CAPITAL LETTER SIGMA
            case 0x03c0: $c = chr(0xf7); break; // GREEK SMALL LETTER PI
            case 0x0304: $c = chr(0xf8); break; // COMBINING MACRON
            case 0x00f7: $c = chr(0xfd); break; // DIVISION SIGN

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

        // Special handling for 'x' followed by COMBINING MACRON
        if ($c == chr(0xf8)) {
            if (strlen($ks0066u) == 0 || substr($ks0066u, strlen($ks0066u) - 1, 1) != 'x') {
                $c = chr(0xff); // BLACK SQUARE
            }

            if (strlen($ks0066u) > 0) {
                $ks0066u = substr($ks0066u, 0, strlen($ks0066u) - 1);
            }
        }

        $ks0066u .= $c;
    }

    return $ks0066u;
}

$ipcon = new IPConnection(); // Create IP connection
$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 autoToKS0066U function to map to the LCD charset
$lcd->writeLine(0, 0, autoToKS0066U("Stromstärke: 17µA"));
$lcd->writeLine(1, 0, autoToKS0066U("Temperatur:  23°C"));

// Write a string directly including characters from the LCD charset
$lcd->writeLine(2, 0, "Drehzahl:   750min\xe9");

echo "Press key to exit\n";
fgetc(fopen('php://stdin', 'r'));
$ipcon->disconnect();

?>

API

Functions that return multiple values return them in an associative array.

Basic Functions

class BrickletLCD20x4(string $uid, IPConnection $ipcon)

Creates an object with the unique device ID $uid:

<?php   $lcd_20x4 = new BrickletLCD20x4('YOUR_DEVICE_UID', $ipcon);   ?>

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

void BrickletLCD20x4::writeLine(int $line, int $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.

void BrickletLCD20x4::clearDisplay()

Deletes all characters from the display.

void BrickletLCD20x4::backlightOn()

Turns the backlight on.

void BrickletLCD20x4::backlightOff()

Turns the backlight off.

bool BrickletLCD20x4::isBacklightOn()

Returns true if the backlight is on and false otherwise.

Advanced Functions

void BrickletLCD20x4::setConfig(bool $cursor, bool $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).

array BrickletLCD20x4::getConfig()

Returns the configuration as set by setConfig().

The returned array has the keys cursor and blinking.

bool BrickletLCD20x4::isButtonPressed(int $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 CALLBACK_BUTTON_PRESSED and CALLBACK_BUTTON_RELEASED callbacks.

void BrickletLCD20x4::setCustomCharacter(int $index, array $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).

array BrickletLCD20x4::getCustomCharacter(int $index)

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

New in version 2.0.1 (Plugin).

void BrickletLCD20x4::setDefaultText(int $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).

string BrickletLCD20x4::getDefaultText(int $line)

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)

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).

int BrickletLCD20x4::getDefaultTextCounter()

Returns the current value of the default text counter.

New in version 2.0.2 (Plugin).

array BrickletLCD20x4::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.

bool BrickletLCD20x4::getResponseExpected(int $function_id)

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.

void BrickletLCD20x4::setResponseExpected(int $function_id, bool $response_expected)

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:

  • 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(bool $response_expected)

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

array BrickletLCD20x4::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 array has the keys uid, connected_uid, position, hardware_version, firmware_version and device_identifier.

Callback Configuration Functions

void BrickletLCD20x4::registerCallback(int $callback_id, callable $callback, mixed $user_data=NULL)

Registers the given $function with the given $callback_id. The optional $user_data will be passed as the last parameter to the function.

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 registerCallback() function of the device object. The first parameter is the callback ID and the second parameter the callback function:

<?php

function myCallback($param)
{
    echo $param . "\n";
}

$lcd_20x4->registerCallback(BrickletLCD20x4::CALLBACK_EXAMPLE, 'myCallback');

?>

The available constants with corresponding function signatures 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.

int BrickletLCD20x4::CALLBACK_BUTTON_PRESSED
<?php   void callback(int $button [, mixed $user_data])   ?>

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).

int BrickletLCD20x4::CALLBACK_BUTTON_RELEASED
<?php   void callback(int $button [, mixed $user_data])   ?>

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).

Constants

int BrickletLCD20x4::DEVICE_IDENTIFIER

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

The getIdentity() function and the CALLBACK_ENUMERATE 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.