C/C++ - LCD 16x2 Bricklet – Tinkerforge

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# C/C++ - LCD 16x2 Bricklet

This is the description of the C/C++ API bindings for the LCD 16x2 Bricklet. General information and technical specifications for the LCD 16x2 Bricklet are summarized in its hardware description.

An installation guide for the C/C++ API bindings is part of their general description.

## Examples

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

### Hello World

Download (example_hello_world.c)

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    #include <stdio.h>

    #include "ip_connection.h"
    #include "bricklet_lcd_16x2.h"

    #define HOST "localhost"
    #define PORT 4223
    #define UID "XYZ" // Change to your UID

    int main() {
        // Create IP connection
        IPConnection ipcon;
        ipcon_create(&ipcon);

        // Create device object
        LCD16x2 lcd;
        lcd_16x2_create(&lcd, UID, &ipcon);

        // Connect to brickd
        if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
            fprintf(stderr, "Could not connect\n");
            exit(1);
        }
        // Don't use device before ipcon is connected

        // Turn backlight on
        lcd_16x2_backlight_on(&lcd);

        // Write "Hello World"
        lcd_16x2_write_line(&lcd, 0, 0, "Hello World");

        printf("Press key to exit\n");
        getchar();
        ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    }

### Button Callbacks

Download (example_button_callbacks.c)

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    #include <stdio.h>

    #include "ip_connection.h"
    #include "bricklet_lcd_16x2.h"

    #define HOST "localhost"
    #define PORT 4223
    #define UID "XYZ" // Change to your UID

    // Callback functions for button status
    void cb_pressed(uint8_t i, void *user_data) {
        (void)user_data; // avoid unused parameter warning

        printf("Pressed: %d\n", i);
    }

    void cb_released(uint8_t i, void *user_data) {
        (void)user_data; // avoid unused parameter warning

        printf("Released: %d\n", i);
    }

    int main() {
        // Create IP connection
        IPConnection ipcon;
        ipcon_create(&ipcon);

        // Create device object
        LCD16x2 lcd;
        lcd_16x2_create(&lcd, UID, &ipcon);

        // Connect to brickd
        if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
            fprintf(stderr, "Could not connect\n");
            exit(1);
        }
        // Don't use device before ipcon is connected

        // Register button status callbacks to cb_pressed and cb_released
        lcd_16x2_register_callback(&lcd,
                                   LCD_16X2_CALLBACK_BUTTON_PRESSED,
                                   (void *)cb_pressed,
                                   NULL);

        lcd_16x2_register_callback(&lcd,
                                   LCD_16X2_CALLBACK_BUTTON_RELEASED,
                                   (void *)cb_released,
                                   NULL);

        printf("Press key to exit\n");
        getchar();
        ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    }

### Unicode

Download (example_unicode.c)

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    #include <stdio.h>
    #include <wchar.h>

    #include "ip_connection.h"
    #include "bricklet_lcd_16x2.h"

    #define HOST "localhost"
    #define PORT 4223
    #define UID "6mJ" // Change to your UID

    // Maps a wchar_t string to the LCD charset
    static void wchar_to_ks0066u(const wchar_t *wchar, char *ks0066u, int ks0066u_length)
    {
        const wchar_t *s = wchar;
        char *d = ks0066u;
        char *e = ks0066u + ks0066u_length;
        char c;
        uint32_t code_point;

        while (*s != '\0' && d < e) {
            // If wchar_t is UTF-16 then handle surrogates
            if (sizeof(wchar_t) == 2 && *s >= 0xd800 && *s <= 0xdbff) {
                code_point = 0x10000 + (*s - 0xd800) * 0x400 + (*(s + 1) - 0xdc00);
                s += 2;
            } else {
                code_point = *s++;
            }

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

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

            // Special handling for 'x' followed by COMBINING MACRON
            if (c == (char)0xf8) {
                if (d == ks0066u || (d > ks0066u && *(d - 1) != 'x')) {
                    c = 0xff; // BLACK SQUARE
                }

                if (d > ks0066u) {
                    --d;
                }
            }

            *d++ = c;
        }

        while (d < e) {
            *d++ = '\0';
        }
    }

    int main() {
        // Create IP connection
        IPConnection ipcon;
        ipcon_create(&ipcon);

        // Create device object
        LCD16x2 lcd;
        lcd_16x2_create(&lcd, UID, &ipcon);

        // Connect to brickd
        if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
            fprintf(stderr, "Could not connect\n");
            exit(1);
        }
        // Don't use device before ipcon is connected

        // Turn backlight on
        lcd_16x2_backlight_on(&lcd);

        // Write a string using the wchar_to_ks0066u function to map to the LCD charset
        char ks0066u[16];

        wchar_to_ks0066u(L"Stromstärke: 5µA", ks0066u, sizeof(ks0066u));
        lcd_16x2_write_line(&lcd, 0, 0, ks0066u);

        // Write a string directly including characters from the LCD charset
        lcd_16x2_write_line(&lcd, 1, 0, "Drehzahl: 1000s\xe9");

        printf("Press key to exit\n");
        getchar();
        ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    }

## API

Every function of the C/C++ bindings returns an integer which describes an error code. Data returned from the device, when a getter is called, is handled via call by reference. These parameters are labeled with the `ret_` prefix.

Possible error codes are:

- E_OK = 0
- E_TIMEOUT = -1
- E_NO_STREAM_SOCKET = -2
- E_HOSTNAME_INVALID = -3
- E_NO_CONNECT = -4
- E_NO_THREAD = -5
- E_NOT_ADDED = -6 (unused since bindings version 2.0.0)
- E_ALREADY_CONNECTED = -7
- E_NOT_CONNECTED = -8
- E_INVALID_PARAMETER = -9
- E_NOT_SUPPORTED = -10
- E_UNKNOWN_ERROR_CODE = -11

as defined in `ip_connection.h`.

All functions listed below are thread-safe.

### Basic Functions

void `lcd_16x2_create`(LCD16x2 *lcd_16x2, const char *uid, IPConnection *ipcon)

  Creates the device object `lcd_16x2` with the unique device ID `uid` and adds it to the IPConnection `ipcon`:

      LCD16x2 lcd_16x2;
      lcd_16x2_create(&lcd_16x2, "YOUR_DEVICE_UID", &ipcon);

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

void `lcd_16x2_destroy`(LCD16x2 *lcd_16x2)

  Removes the device object `lcd_16x2` from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int `lcd_16x2_write_line`(LCD16x2 *lcd_16x2, uint8_t line, uint8_t position, const char text[16])

  Writes text to a specific line (0 to 1) with a specific position (0 to 15). The text can have a maximum of 16 characters.

  For example: (0, 5, "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.

int `lcd_16x2_clear_display`(LCD16x2 *lcd_16x2)

  Deletes all characters from the display.

int `lcd_16x2_backlight_on`(LCD16x2 *lcd_16x2)

  Turns the backlight on.

int `lcd_16x2_backlight_off`(LCD16x2 *lcd_16x2)

  Turns the backlight off.

int `lcd_16x2_is_backlight_on`(LCD16x2 *lcd_16x2, bool *ret_backlight)

  Returns true if the backlight is on and false otherwise.

### Advanced Functions

int `lcd_16x2_set_config`(LCD16x2 *lcd_16x2, 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 `lcd_16x2_write_line()`.

  The default is (false, false).

int `lcd_16x2_get_config`(LCD16x2 *lcd_16x2, bool *ret_cursor, bool *ret_blinking)

  Returns the configuration as set by `lcd_16x2_set_config()`.

int `lcd_16x2_is_button_pressed`(LCD16x2 *lcd_16x2, uint8_t button, bool *ret_pressed)

  Returns true if the button (0 to 2) is pressed. If you want to react on button presses and releases it is recommended to use the `LCD_16X2_CALLBACK_BUTTON_PRESSED` and `LCD_16X2_CALLBACK_BUTTON_RELEASED` callbacks.

int `lcd_16x2_set_custom_character`(LCD16x2 *lcd_16x2, uint8_t index, uint8_t character[8])

  The LCD 16x2 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 `lcd_16x2_write_line()` by using the characters with the byte representation 8 to 15.

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

int `lcd_16x2_get_custom_character`(LCD16x2 *lcd_16x2, uint8_t index, uint8_t ret_character[8])

  Returns the custom character for a given index, as set with `lcd_16x2_set_custom_character()`.

  New in version 2.0.1 (Plugin).

int `lcd_16x2_get_api_version`(LCD16x2 *lcd_16x2, uint8_t ret_api_version[3])

  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.

int `lcd_16x2_get_response_expected`(LCD16x2 *lcd_16x2, uint8_t function_id, bool *ret_response_expected)

  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 `lcd_16x2_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.

  See `lcd_16x2_set_response_expected()` for the list of function ID defines available for this function.

int `lcd_16x2_set_response_expected`(LCD16x2 *lcd_16x2, uint8_t 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 and callbacks it is always disabled.

  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 defines are available for this function:

  - LCD_16X2_FUNCTION_WRITE_LINE = 1
  - LCD_16X2_FUNCTION_CLEAR_DISPLAY = 2
  - LCD_16X2_FUNCTION_BACKLIGHT_ON = 3
  - LCD_16X2_FUNCTION_BACKLIGHT_OFF = 4
  - LCD_16X2_FUNCTION_SET_CONFIG = 6
  - LCD_16X2_FUNCTION_SET_CUSTOM_CHARACTER = 11

int `lcd_16x2_set_response_expected_all`(LCD16x2 *lcd_16x2, bool response_expected)

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

int `lcd_16x2_get_identity`(LCD16x2 *lcd_16x2, char ret_uid[8], char ret_connected_uid[8], char *ret_position, uint8_t ret_hardware_version[3], uint8_t ret_firmware_version[3], uint16_t *ret_device_identifier)

  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.

### Callback Configuration Functions

void `lcd_16x2_register_callback`(LCD16x2 *lcd_16x2, uint8_t id, void *callback, void *user_data)

  Registers a callback with ID `id` to the function `callback`. The `user_data` will be given as a parameter of the callback.

  The available 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 `lcd_16x2_register_callback()` function. The parameters consist of the device object, the callback ID, the callback function and optional user data:

>     void my_callback(int p, void *user_data) {
>         printf("parameter: %d\n", p);
>     }

>     lcd_16x2_register_callback(&lcd_16x2, LCD_16X2_CALLBACK_EXAMPLE, (void *)my_callback, NULL);

The available constants with corresponding callback 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.

`LCD_16X2_CALLBACK_BUTTON_PRESSED`

      void callback(uint8_t button, void *user_data)

  This callback is triggered when a button is pressed. The parameter is the number of the button (0 to 2).

`LCD_16X2_CALLBACK_BUTTON_RELEASED`

      void callback(uint8_t button, void *user_data)

  This callback is triggered when a button is released. The parameter is the number of the button (0 to 2).

### Constants

`LCD_16X2_DEVICE_IDENTIFIER`

  This constant is used to identify a LCD 16x2 Bricklet.

  The `lcd_16x2_get_identity()` function and the `IPCON_CALLBACK_ENUMERATE` callback of the IP Connection have a `device_identifier` parameter to specify the Brick's or Bricklet's type.

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