Rust - LCD 20x4 Bricklet

This is the description of the Rust 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 Rust API bindings is part of their general description. Additional documentation can be found on docs.rs.

Examples

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

Hello World

Download (example_hello_world.rs)

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use std::{error::Error, io};

use tinkerforge::{ip_connection::IpConnection, lcd_20x4_bricklet::*};

const HOST: &str = "localhost";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your LCD 20x4 Bricklet.

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection.
    let lcd = Lcd20x4Bricklet::new(UID, &ipcon); // Create device object.

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

    // Turn backlight on
    lcd.backlight_on();

    // Write "Hello World"
    lcd.write_line(0, 0, "Hello World".to_string());

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

Button Callback

Download (example_button_callback.rs)

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use std::{error::Error, io, thread};
use tinkerforge::{ip_connection::IpConnection, lcd_20x4_bricklet::*};

const HOST: &str = "localhost";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your LCD 20x4 Bricklet.

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection.
    let lcd = Lcd20x4Bricklet::new(UID, &ipcon); // Create device object.

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

    let button_pressed_receiver = lcd.get_button_pressed_callback_receiver();

    // Spawn thread to handle received callback messages.
    // This thread ends when the `lcd` object
    // is dropped, so there is no need for manual cleanup.
    thread::spawn(move || {
        for button_pressed in button_pressed_receiver {
            println!("Button Pressed: {}", button_pressed);
        }
    });

    let button_released_receiver = lcd.get_button_released_callback_receiver();

    // Spawn thread to handle received callback messages.
    // This thread ends when the `lcd` object
    // is dropped, so there is no need for manual cleanup.
    thread::spawn(move || {
        for button_released in button_released_receiver {
            println!("Button Released: {}", button_released);
        }
    });

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

Unicode

Download (example_unicode.rs)

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use std::{error::Error, io};

use tinkerforge::{ip_connection::IpConnection, lcd_20x4_bricklet::*};

const HOST: &str = "127.0.0.1";
const PORT: u16 = 4223;
const UID: &str = "XYZ"; // Change XYZ to the UID of your LCD 20x4 Bricklet

/// Maps a normal UTF-8 encoded string to the LCD charset.
fn utf8_to_ks0066u(utf8: &str) -> String {
    let mut result = Vec::<char>::with_capacity(utf8.len());
    for code_point in utf8.chars() {
        // Technically these are not code points, but scalar values.
        let mut replacement = match code_point as u32 {
            // ASCII subset from JIS X 0201
            // The LCD charset doesn't include '\' and '~', use similar characters instead
            0x005c => 0xa4, // REVERSE SOLIDUS maps to IDEOGRAPHIC COMMA
            0x007e => 0x2d, // TILDE maps to HYPHEN-MINUS
            0x0020...0x007e => code_point as u32,

            // Katakana subset from JIS X 0201
            0xff61...0xff9f => code_point as u32 - 0xfec0,

            // Special characters
            0x00a5 => 0x5c, // YEN SIGN
            0x2192 => 0x7e, // RIGHTWARDS ARROW
            0x2190 => 0x7f, // LEFTWARDS ARROW
            0x00b0 => 0xdf, // DEGREE SIGN maps to KATAKANA SEMI-VOICED SOUND MARK
            0x03b1 => 0xe0, // GREEK SMALL LETTER ALPHA
            0x00c4 => 0xe1, // LATIN CAPITAL LETTER A WITH DIAERESIS
            0x00e4 => 0xe1, // LATIN SMALL LETTER A WITH DIAERESIS
            0x00df => 0xe2, // LATIN SMALL LETTER SHARP S
            0x03b5 => 0xe3, // GREEK SMALL LETTER EPSILON
            0x00b5 => 0xe4, // MICRO SIGN
            0x03bc => 0xe4, // GREEK SMALL LETTER MU
            0x03c2 => 0xe5, // GREEK SMALL LETTER FINAL SIGMA
            0x03c1 => 0xe6, // GREEK SMALL LETTER RHO
            0x221a => 0xe8, // SQUARE ROOT
            0x00b9 => 0xe9, // SUPERSCRIPT ONE maps to SUPERSCRIPT (minus) ONE
            0x00a4 => 0xeb, // CURRENCY SIGN
            0x00a2 => 0xec, // CENT SIGN
            0x2c60 => 0xed, // LATIN CAPITAL LETTER L WITH DOUBLE BAR
            0x00f1 => 0xee, // LATIN SMALL LETTER N WITH TILDE
            0x00d6 => 0xef, // LATIN CAPITAL LETTER O WITH DIAERESIS
            0x00f6 => 0xef, // LATIN SMALL LETTER O WITH DIAERESIS
            0x03f4 => 0xf2, // GREEK CAPITAL THETA SYMBOL
            0x221e => 0xf3, // INFINITY
            0x03a9 => 0xf4, // GREEK CAPITAL LETTER OMEGA
            0x00dc => 0xf5, // LATIN CAPITAL LETTER U WITH DIAERESIS
            0x00fc => 0xf5, // LATIN SMALL LETTER U WITH DIAERESIS
            0x03a3 => 0xf6, // GREEK CAPITAL LETTER SIGMA
            0x03c0 => 0xf7, // GREEK SMALL LETTER PI
            0x0304 => 0xf8, // COMBINING MACRON
            0x00f7 => 0xfd, // DIVISION SIGN

            // Default
            _ => 0xff, // BLACK SQUARE
        };

        // Special handling for 'x' followed by COMBINING MACRON
        if replacement == 0xf8 {
            if result[result.len() - 1] != 'x' {
                replacement = 0xff; // BLACK SQUARE
            }

            if result.len() > 0 {
                result.truncate(result.len() - 1);
            }
        }
        result.push(std::char::from_u32(replacement).unwrap());
    }

    result.into_iter().collect()
}

fn main() -> Result<(), Box<dyn Error>> {
    let ipcon = IpConnection::new(); // Create IP connection
    let lcd = Lcd20x4Bricklet::new(UID, &ipcon); // Create device object

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

    // Turn backlight on
    lcd.backlight_on();

    // Write some strings using the utf8_to_ks0066u function to map to the LCD charset
    lcd.write_line(0, 0, utf8_to_ks0066u("Stromstärke: 17µA"));
    lcd.write_line(1, 0, utf8_to_ks0066u("Temperatur:  23°C"));

    // Write a string directly including characters from the LCD charset. \u{00e9} is the ⁻¹ character.
    lcd.write_line(2, 0, "Drehzahl: 750min\u{00e9}".to_string());

    println!("Press enter to exit.");
    let mut _input = String::new();
    io::stdin().read_line(&mut _input)?;
    ipcon.disconnect();
    Ok(())
}

API

To allow non-blocking usage, nearly every function of the Rust bindings returns a wrapper around a mpsc::Receiver. To block until the function has finished and get your result, call one of the receiver's recv variants. Those return either the result sent by the device, or any error occured.

Functions returning a result directly will block until the device has finished processing the request.

All functions listed below are thread-safe, those which return a receiver are lock-free.

Basic Functions

pub fn Lcd20x4Bricklet::new(uid: &str, ip_connection: &IpConnection) → Lcd20x4Bricklet
Parameters:
  • uid – Type: &str
  • ip_connection – Type: &IPConnection
Returns:
  • lcd_20x4 – Type: Lcd20x4Bricklet

Creates a new Lcd20x4Bricklet object with the unique device ID uid and adds it to the IPConnection ip_connection:

let lcd_20x4 = Lcd20x4Bricklet::new("YOUR_DEVICE_UID", &ip_connection);

This device object can be used after the IP connection has been connected (see examples above).

pub fn Lcd20x4Bricklet::write_line(&self, line: u8, position: u8, text: String) → ConvertingReceiver<()>
Parameters:
  • line – Type: u8, Range: [0 to 255]
  • position – Type: u8, Range: [0 to 255]
  • text – Type: String, Length: up to 20

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.

pub fn Lcd20x4Bricklet::clear_display(&self) → ConvertingReceiver<()>

Deletes all characters from the display.

pub fn Lcd20x4Bricklet::backlight_on(&self) → ConvertingReceiver<()>

Turns the backlight on.

pub fn Lcd20x4Bricklet::backlight_off(&self) → ConvertingReceiver<()>

Turns the backlight off.

pub fn Lcd20x4Bricklet::is_backlight_on(&self) → ConvertingReceiver<bool>
Returns:
  • backlight – Type: bool

Returns true if the backlight is on and false otherwise.

Advanced Functions

pub fn Lcd20x4Bricklet::set_config(&self, cursor: bool, blinking: bool) → ConvertingReceiver<()>
Parameters:
  • cursor – Type: bool
  • blinking – Type: bool

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 Lcd20x4Bricklet::write_line.

The default is (false, false).

pub fn Lcd20x4Bricklet::get_config(&self) → ConvertingReceiver<Config>
Return Object:
  • cursor – Type: bool
  • blinking – Type: bool

Returns the configuration as set by Lcd20x4Bricklet::set_config.

pub fn Lcd20x4Bricklet::is_button_pressed(&self, button: u8) → ConvertingReceiver<bool>
Parameters:
  • button – Type: u8, Range: [0 to 255]
Returns:
  • pressed – Type: bool

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 Lcd20x4Bricklet::get_button_pressed_callback_receiver and Lcd20x4Bricklet::get_button_released_callback_receiver callbacks.

pub fn Lcd20x4Bricklet::set_custom_character(&self, index: u8, character: [u8; 8]) → ConvertingReceiver<()>
Parameters:
  • index – Type: u8, Range: [0 to 255]
  • character – Type: [u8; 8], Range: [0 to 255]

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 Lcd20x4Bricklet::write_line 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).

pub fn Lcd20x4Bricklet::get_custom_character(&self, index: u8) → ConvertingReceiver<[u8; 8]>
Parameters:
  • index – Type: u8, Range: [0 to 255]
Returns:
  • character – Type: [u8; 8], Range: [0 to 255]

Returns the custom character for a given index, as set with Lcd20x4Bricklet::set_custom_character.

New in version 2.0.1 (Plugin).

pub fn Lcd20x4Bricklet::set_default_text(&self, line: u8, text: String) → ConvertingReceiver<()>
Parameters:
  • line – Type: u8, Range: [0 to 255]
  • 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 Lcd20x4Bricklet::set_default_text_counter.

New in version 2.0.2 (Plugin).

pub fn Lcd20x4Bricklet::get_default_text(&self, line: u8) → ConvertingReceiver<String>
Parameters:
  • line – Type: u8, Range: [0 to 255]
Returns:
  • text – Type: String, Length: up to 20

Returns the default text for a given line (0-3) as set by Lcd20x4Bricklet::set_default_text.

New in version 2.0.2 (Plugin).

pub fn Lcd20x4Bricklet::set_default_text_counter(&self, counter: i32) → ConvertingReceiver<()>
Parameters:
  • counter – Type: i32, Range: [-231 to 231 - 1]

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 Lcd20x4Bricklet::set_default_text) 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 Lcd20x4Bricklet::set_default_text_counter 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).

pub fn Lcd20x4Bricklet::get_default_text_counter(&self) → ConvertingReceiver<i32>
Returns:
  • counter – Type: i32, Range: [-231 to 231 - 1]

Returns the current value of the default text counter.

New in version 2.0.2 (Plugin).

pub fn Lcd20x4Bricklet::get_api_version(&self) → [u8; 3]
Returns:
  • api_version – Type: [u8; 3], Range: [0 to 255]

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.

pub fn Lcd20x4Bricklet::get_response_expected(&mut self, function_id: u8) → bool
Parameters:
  • function_id – Type: u8, Range: See constants
Returns:
  • response_expected – Type: bool

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 Lcd20x4Bricklet::set_response_expected. 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:

  • LCD_20X4_BRICKLET_FUNCTION_WRITE_LINE = 1
  • LCD_20X4_BRICKLET_FUNCTION_CLEAR_DISPLAY = 2
  • LCD_20X4_BRICKLET_FUNCTION_BACKLIGHT_ON = 3
  • LCD_20X4_BRICKLET_FUNCTION_BACKLIGHT_OFF = 4
  • LCD_20X4_BRICKLET_FUNCTION_SET_CONFIG = 6
  • LCD_20X4_BRICKLET_FUNCTION_SET_CUSTOM_CHARACTER = 11
  • LCD_20X4_BRICKLET_FUNCTION_SET_DEFAULT_TEXT = 13
  • LCD_20X4_BRICKLET_FUNCTION_SET_DEFAULT_TEXT_COUNTER = 15
pub fn Lcd20x4Bricklet::set_response_expected(&mut self, function_id: u8, response_expected: bool) → ()
Parameters:
  • function_id – Type: u8, Range: See constants
  • response_expected – Type: bool

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:

  • LCD_20X4_BRICKLET_FUNCTION_WRITE_LINE = 1
  • LCD_20X4_BRICKLET_FUNCTION_CLEAR_DISPLAY = 2
  • LCD_20X4_BRICKLET_FUNCTION_BACKLIGHT_ON = 3
  • LCD_20X4_BRICKLET_FUNCTION_BACKLIGHT_OFF = 4
  • LCD_20X4_BRICKLET_FUNCTION_SET_CONFIG = 6
  • LCD_20X4_BRICKLET_FUNCTION_SET_CUSTOM_CHARACTER = 11
  • LCD_20X4_BRICKLET_FUNCTION_SET_DEFAULT_TEXT = 13
  • LCD_20X4_BRICKLET_FUNCTION_SET_DEFAULT_TEXT_COUNTER = 15
pub fn Lcd20x4Bricklet::set_response_expected_all(&mut self, response_expected: bool) → ()
Parameters:
  • response_expected – Type: bool

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

pub fn Lcd20x4Bricklet::get_identity(&self) → ConvertingReceiver<Identity>
Return Object:
  • uid – Type: String, Length: up to 8
  • connected_uid – Type: String, Length: up to 8
  • position – Type: char
  • hardware_version – Type: [u8; 3], Range: [0 to 255]
  • firmware_version – Type: [u8; 3], Range: [0 to 255]
  • device_identifier – Type: u16, 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' or 'd'.

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 the corresponding get_*_callback_receiver function, which returns a receiver for callback events.

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.

pub fn Lcd20x4Bricklet::get_button_pressed_callback_receiver(&self) → ConvertingCallbackReceiver<u8>
Event:
  • button – Type: u8, Range: [0 to 255]

Receivers created with this function receive Button Pressed events.

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

pub fn Lcd20x4Bricklet::get_button_released_callback_receiver(&self) → ConvertingCallbackReceiver<u8>
Event:
  • button – Type: u8, Range: [0 to 255]

Receivers created with this function receive Button Released events.

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

Constants

pub const Lcd20x4Bricklet::DEVICE_IDENTIFIER

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

The Lcd20x4Bricklet::get_identity function and the IpConnection::get_enumerate_callback_receiver callback of the IP Connection have a device_identifier parameter to specify the Brick's or Bricklet's type.

pub const Lcd20x4Bricklet::DEVICE_DISPLAY_NAME

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