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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)

 1#include <stdio.h>
 2
 3#include "ip_connection.h"
 4#include "bricklet_lcd_16x2.h"
 5
 6#define HOST "localhost"
 7#define PORT 4223
 8#define UID "XYZ" // Change XYZ to the UID of your LCD 16x2 Bricklet
 9
10int main(void) {
11    // Create IP connection
12    IPConnection ipcon;
13    ipcon_create(&ipcon);
14
15    // Create device object
16    LCD16x2 lcd;
17    lcd_16x2_create(&lcd, UID, &ipcon);
18
19    // Connect to brickd
20    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
21        fprintf(stderr, "Could not connect\n");
22        return 1;
23    }
24    // Don't use device before ipcon is connected
25
26    // Turn backlight on
27    lcd_16x2_backlight_on(&lcd);
28
29    // Write "Hello World"
30    lcd_16x2_write_line(&lcd, 0, 0, "Hello World");
31
32    printf("Press key to exit\n");
33    getchar();
34    lcd_16x2_destroy(&lcd);
35    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
36    return 0;
37}

Button Callback

Download (example_button_callback.c)

 1#include <stdio.h>
 2
 3#include "ip_connection.h"
 4#include "bricklet_lcd_16x2.h"
 5
 6#define HOST "localhost"
 7#define PORT 4223
 8#define UID "XYZ" // Change XYZ to the UID of your LCD 16x2 Bricklet
 9
10// Callback function for button pressed callback
11void cb_button_pressed(uint8_t button, void *user_data) {
12    (void)user_data; // avoid unused parameter warning
13
14    printf("Button Pressed: %u\n", button);
15}
16
17// Callback function for button released callback
18void cb_button_released(uint8_t button, void *user_data) {
19    (void)user_data; // avoid unused parameter warning
20
21    printf("Button Released: %u\n", button);
22}
23
24int main(void) {
25    // Create IP connection
26    IPConnection ipcon;
27    ipcon_create(&ipcon);
28
29    // Create device object
30    LCD16x2 lcd;
31    lcd_16x2_create(&lcd, UID, &ipcon);
32
33    // Connect to brickd
34    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
35        fprintf(stderr, "Could not connect\n");
36        return 1;
37    }
38    // Don't use device before ipcon is connected
39
40    // Register button pressed callback to function cb_button_pressed
41    lcd_16x2_register_callback(&lcd,
42                               LCD_16X2_CALLBACK_BUTTON_PRESSED,
43                               (void (*)(void))cb_button_pressed,
44                               NULL);
45
46    // Register button released callback to function cb_button_released
47    lcd_16x2_register_callback(&lcd,
48                               LCD_16X2_CALLBACK_BUTTON_RELEASED,
49                               (void (*)(void))cb_button_released,
50                               NULL);
51
52    printf("Press key to exit\n");
53    getchar();
54    lcd_16x2_destroy(&lcd);
55    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
56    return 0;
57}

Unicode

Download (example_unicode.c)

  1#include <stdio.h>
  2#include <wchar.h>
  3
  4#include "ip_connection.h"
  5#include "bricklet_lcd_16x2.h"
  6
  7#define HOST "localhost"
  8#define PORT 4223
  9#define UID "XYZ" // Change XYZ to the UID of your LCD 16x2 Bricklet
 10
 11// Maps a wchar_t string to the LCD charset
 12static void wchar_to_ks0066u(const wchar_t *wchar, char *ks0066u, int ks0066u_length)
 13{
 14    const wchar_t *s = wchar;
 15    char *d = ks0066u;
 16    char *e = ks0066u + ks0066u_length;
 17    char c;
 18    uint32_t code_point;
 19
 20    while (*s != '\0' && d < e) {
 21        // If wchar_t is UTF-16 then handle surrogates
 22        if (sizeof(wchar_t) == 2 && *s >= 0xd800 && *s <= 0xdbff) {
 23            code_point = 0x10000 + (*s - 0xd800) * 0x400 + (*(s + 1) - 0xdc00);
 24            s += 2;
 25        } else {
 26            code_point = *s++;
 27        }
 28
 29        // ASCII subset from JIS X 0201
 30        if (code_point >= 0x0020 && code_point <= 0x007e) {
 31            // The LCD charset doesn't include '\' and '~', use similar characters instead
 32            switch (code_point) {
 33            case 0x005c: c = 0xa4; break; // REVERSE SOLIDUS maps to IDEOGRAPHIC COMMA
 34            case 0x007e: c = 0x2d; break; // TILDE maps to HYPHEN-MINUS
 35            default: c = code_point; break;
 36            }
 37        }
 38        // Katakana subset from JIS X 0201
 39        else if (code_point >= 0xff61 && code_point <= 0xff9f) {
 40            c = code_point - 0xfec0;
 41        }
 42        // Special characters
 43        else {
 44            switch (code_point) {
 45            case 0x00a5: c = 0x5c; break; // YEN SIGN
 46            case 0x2192: c = 0x7e; break; // RIGHTWARDS ARROW
 47            case 0x2190: c = 0x7f; break; // LEFTWARDS ARROW
 48            case 0x00b0: c = 0xdf; break; // DEGREE SIGN maps to KATAKANA SEMI-VOICED SOUND MARK
 49            case 0x03b1: c = 0xe0; break; // GREEK SMALL LETTER ALPHA
 50            case 0x00c4: c = 0xe1; break; // LATIN CAPITAL LETTER A WITH DIAERESIS
 51            case 0x00e4: c = 0xe1; break; // LATIN SMALL LETTER A WITH DIAERESIS
 52            case 0x00df: c = 0xe2; break; // LATIN SMALL LETTER SHARP S
 53            case 0x03b5: c = 0xe3; break; // GREEK SMALL LETTER EPSILON
 54            case 0x00b5: c = 0xe4; break; // MICRO SIGN
 55            case 0x03bc: c = 0xe4; break; // GREEK SMALL LETTER MU
 56            case 0x03c2: c = 0xe5; break; // GREEK SMALL LETTER FINAL SIGMA
 57            case 0x03c1: c = 0xe6; break; // GREEK SMALL LETTER RHO
 58            case 0x221a: c = 0xe8; break; // SQUARE ROOT
 59            case 0x00b9: c = 0xe9; break; // SUPERSCRIPT ONE maps to SUPERSCRIPT (minus) ONE
 60            case 0x00a4: c = 0xeb; break; // CURRENCY SIGN
 61            case 0x00a2: c = 0xec; break; // CENT SIGN
 62            case 0x2c60: c = 0xed; break; // LATIN CAPITAL LETTER L WITH DOUBLE BAR
 63            case 0x00f1: c = 0xee; break; // LATIN SMALL LETTER N WITH TILDE
 64            case 0x00d6: c = 0xef; break; // LATIN CAPITAL LETTER O WITH DIAERESIS
 65            case 0x00f6: c = 0xef; break; // LATIN SMALL LETTER O WITH DIAERESIS
 66            case 0x03f4: c = 0xf2; break; // GREEK CAPITAL THETA SYMBOL
 67            case 0x221e: c = 0xf3; break; // INFINITY
 68            case 0x03a9: c = 0xf4; break; // GREEK CAPITAL LETTER OMEGA
 69            case 0x00dc: c = 0xf5; break; // LATIN CAPITAL LETTER U WITH DIAERESIS
 70            case 0x00fc: c = 0xf5; break; // LATIN SMALL LETTER U WITH DIAERESIS
 71            case 0x03a3: c = 0xf6; break; // GREEK CAPITAL LETTER SIGMA
 72            case 0x03c0: c = 0xf7; break; // GREEK SMALL LETTER PI
 73            case 0x0304: c = 0xf8; break; // COMBINING MACRON
 74            case 0x00f7: c = 0xfd; break; // DIVISION SIGN
 75
 76            default:
 77            case 0x25a0: c = 0xff; break; // BLACK SQUARE
 78            }
 79        }
 80
 81        // Special handling for 'x' followed by COMBINING MACRON
 82        if (c == (char)0xf8) {
 83            if (d == ks0066u || (d > ks0066u && *(d - 1) != 'x')) {
 84                c = 0xff; // BLACK SQUARE
 85            }
 86
 87            if (d > ks0066u) {
 88                --d;
 89            }
 90        }
 91
 92        *d++ = c;
 93    }
 94
 95    while (d < e) {
 96        *d++ = '\0';
 97    }
 98}
 99
100int main(void) {
101    // Create IP connection
102    IPConnection ipcon;
103    ipcon_create(&ipcon);
104
105    // Create device object
106    LCD16x2 lcd;
107    lcd_16x2_create(&lcd, UID, &ipcon);
108
109    // Connect to brickd
110    if(ipcon_connect(&ipcon, HOST, PORT) < 0) {
111        fprintf(stderr, "Could not connect\n");
112        return 1;
113    }
114    // Don't use device before ipcon is connected
115
116    // Turn backlight on
117    lcd_16x2_backlight_on(&lcd);
118
119    // Write a string using the wchar_to_ks0066u function to map to the LCD charset
120    char ks0066u[16];
121
122    wchar_to_ks0066u(L"Stromstärke: 5µA", ks0066u, sizeof(ks0066u));
123    lcd_16x2_write_line(&lcd, 0, 0, ks0066u);
124
125    // Write a string directly including characters from the LCD charset
126    lcd_16x2_write_line(&lcd, 1, 0, "Drehzahl: 1000s\xe9");
127
128    printf("Press key to exit\n");
129    getchar();
130    lcd_16x2_destroy(&lcd);
131    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
132    return 0;
133}

API

Most functions of the C/C++ bindings return an error code (e_code). Data returned from the device, when a getter is called, is handled via output parameters. 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 C/C++ 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

  • E_STREAM_OUT_OF_SYNC = -12

  • E_INVALID_UID = -13

  • E_NON_ASCII_CHAR_IN_SECRET = -14

  • E_WRONG_DEVICE_TYPE = -15

  • E_DEVICE_REPLACED = -16

  • E_WRONG_RESPONSE_LENGTH = -17

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)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • uid – Type: const char *
  • ipcon – Type: IPConnection *

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.

void lcd_16x2_destroy(LCD16x2 *lcd_16x2)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *

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)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • line – Type: uint8_t, Range: [0 to 1]
  • position – Type: uint8_t, Range: [0 to 15]
  • text – Type: const char[16]
Returns:
  • e_code – Type: int

Writes text to a specific line with a specific position. 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)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
Returns:
  • e_code – Type: int

Deletes all characters from the display.

int lcd_16x2_backlight_on(LCD16x2 *lcd_16x2)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
Returns:
  • e_code – Type: int

Turns the backlight on.

int lcd_16x2_backlight_off(LCD16x2 *lcd_16x2)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
Returns:
  • e_code – Type: int

Turns the backlight off.

int lcd_16x2_is_backlight_on(LCD16x2 *lcd_16x2, bool *ret_backlight)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
Output Parameters:
  • ret_backlight – Type: bool
Returns:
  • e_code – Type: int

Returns true if the backlight is on and false otherwise.

Advanced Functions

int lcd_16x2_set_config(LCD16x2 *lcd_16x2, bool cursor, bool blinking)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • cursor – Type: bool, Default: false
  • blinking – Type: bool, Default: false
Returns:
  • e_code – Type: int

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().

int lcd_16x2_get_config(LCD16x2 *lcd_16x2, bool *ret_cursor, bool *ret_blinking)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
Output Parameters:
  • ret_cursor – Type: bool, Default: false
  • ret_blinking – Type: bool, Default: false
Returns:
  • e_code – Type: int

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)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • button – Type: uint8_t, Range: [0 to 2]
Output Parameters:
  • ret_pressed – Type: bool
Returns:
  • e_code – Type: int

Returns true if the button 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])
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • index – Type: uint8_t, Range: [0 to 7]
  • character – Type: uint8_t[8], Range: [0 to 31]
Returns:
  • e_code – Type: int

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 ("\x08" or "\u0008") to 15 ("\x0F" or "\u000F").

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.

Added in version 2.0.1$nbsp;(Plugin).

int lcd_16x2_get_custom_character(LCD16x2 *lcd_16x2, uint8_t index, uint8_t ret_character[8])
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • index – Type: uint8_t, Range: [0 to 7]
Output Parameters:
  • ret_character – Type: uint8_t[8], Range: [0 to 31]
Returns:
  • e_code – Type: int

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

Added in version 2.0.1$nbsp;(Plugin).

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)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
Output Parameters:
  • ret_uid – Type: char[8]
  • ret_connected_uid – Type: char[8]
  • ret_position – Type: char, Range: ['a' to 'h', 'z']
  • ret_hardware_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
  • ret_firmware_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
  • ret_device_identifier – Type: uint16_t, Range: [0 to 216 - 1]
Returns:
  • e_code – Type: int

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). A Bricklet connected to an Isolator Bricklet is always at 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

void lcd_16x2_register_callback(LCD16x2 *lcd_16x2, int16_t callback_id, void (*function)(void), void *user_data)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • callback_id – Type: int16_t
  • function – Type: void (*)(void)
  • user_data – Type: void *

Registers the given function with the given callback_id. The 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 lcd_16x2_register_callback() function:

void my_callback(int value, void *user_data) {
    printf("Value: %d\n", value);
}

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

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.

LCD_16X2_CALLBACK_BUTTON_PRESSED
void callback(uint8_t button, void *user_data)
Callback Parameters:
  • button – Type: uint8_t, Range: [0 to 2]
  • user_data – Type: void *

This callback is triggered when a button is pressed. The parameter is the number of the button.

LCD_16X2_CALLBACK_BUTTON_RELEASED
void callback(uint8_t button, void *user_data)
Callback Parameters:
  • button – Type: uint8_t, Range: [0 to 2]
  • user_data – Type: void *

This callback is triggered when a button is released. The parameter is the number of the button.

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.

int lcd_16x2_get_api_version(LCD16x2 *lcd_16x2, uint8_t ret_api_version[3])
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
Output Parameters:
  • ret_api_version – Type: uint8_t[3]
    • 0: major – Type: uint8_t, Range: [0 to 255]
    • 1: minor – Type: uint8_t, Range: [0 to 255]
    • 2: revision – Type: uint8_t, Range: [0 to 255]
Returns:
  • e_code – Type: int

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.

int lcd_16x2_get_response_expected(LCD16x2 *lcd_16x2, uint8_t function_id, bool *ret_response_expected)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • function_id – Type: uint8_t, Range: See constants
Output Parameters:
  • ret_response_expected – Type: bool
Returns:
  • e_code – Type: int

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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • 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(LCD16x2 *lcd_16x2, uint8_t function_id, bool response_expected)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • function_id – Type: uint8_t, Range: See constants
  • response_expected – Type: bool
Returns:
  • e_code – Type: int

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 sent and errors are silently ignored, because they cannot be detected.

The following constants are available for this function:

For function_id:

  • 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)
Parameters:
  • lcd_16x2 – Type: LCD16x2 *
  • response_expected – Type: bool
Returns:
  • e_code – Type: int

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

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.

LCD_16X2_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a LCD 16x2 Bricklet.