C/C++ - OLED 128x64 Bricklet

This is the description of the C/C++ API bindings for the OLED 128x64 Bricklet. General information and technical specifications for the OLED 128x64 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_oled_128x64.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your OLED 128x64 Bricklet

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

    // Create device object
    OLED128x64 oled;
    oled_128x64_create(&oled, UID, &ipcon);

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

    // Clear display
    oled_128x64_clear_display(&oled);

    // Write "Hello World" starting from upper left corner of the screen
    oled_128x64_write_line(&oled, 0, 0, "Hello World");

    printf("Press key to exit\n");
    getchar();
    oled_128x64_destroy(&oled);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

Pixel Matrix

Download (example_pixel_matrix.c)

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#include <stdio.h>

#include "ip_connection.h"
#include "bricklet_oled_128x64.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change XYZ to the UID of your OLED 128x64 Bricklet
#define WIDTH 128
#define HEIGHT 64

void draw_matrix(OLED128x64 *oled, bool pixels[HEIGHT][WIDTH]) {
    uint8_t pages[HEIGHT / 8][WIDTH];
    int row, column, bit;

    // Convert pixels into pages
    for (row = 0; row < HEIGHT / 8; row++) {
        for (column = 0; column < WIDTH; column++) {
            pages[row][column] = 0;

            for (bit = 0; bit < 8; bit++) {
                if (pixels[(row * 8) + bit][column]) {
                    pages[row][column] |= 1 << bit;
                }
            }
        }
    }

    // Write all pages
    oled_128x64_new_window(oled, 0, WIDTH - 1, 0, HEIGHT / 8 - 1);

    for (row = 0; row < HEIGHT / 8; row++) {
        for (column = 0; column < WIDTH; column += 64) {
            oled_128x64_write(oled, &pages[row][column]);
        }
    }
}

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

    // Create device object
    OLED128x64 oled;
    oled_128x64_create(&oled, UID, &ipcon);

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

    // Clear display
    oled_128x64_clear_display(&oled);

    // Draw checkerboard pattern
    int row, column;
    bool pixels[HEIGHT][WIDTH];

    for (row = 0; row < HEIGHT; row++) {
        for (column = 0; column < WIDTH; column++) {
            pixels[row][column] = (row / 8) % 2 == (column / 8) % 2;
        }
    }

    draw_matrix(&oled, pixels);

    printf("Press key to exit\n");
    getchar();
    oled_128x64_destroy(&oled);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

Scribble

Download (example_scribble.c)

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#include <stdio.h>
#include <math.h>
#include <gd.h> // https://libgd.github.io/

#define IPCON_EXPOSE_MILLISLEEP

#include "ip_connection.h"
#include "bricklet_oled_128x64.h"

#define HOST "localhost"
#define PORT 4223
#define UID "XYZ" // Change to your UID
#define WIDTH 128
#define HEIGHT 64

void draw_image(OLED128x64 *oled, gdImagePtr image) {
    uint8_t pages[HEIGHT / 8][WIDTH];
    int row, column, bit, index;

    // Convert pixels into pages
    for (row = 0; row < HEIGHT / 8; row++) {
        for (column = 0; column < WIDTH; column++) {
            pages[row][column] = 0;

            for (bit = 0; bit < 8; bit++) {
                index = gdImageGetPixel(image, column, (row * 8) + bit);

                if (gdImageRed(image, index) > 0) {
                    pages[row][column] |= 1 << bit;
                }
            }
        }
    }

    // Write all pages
    oled_128x64_new_window(oled, 0, WIDTH - 1, 0, HEIGHT / 8 - 1);

    for (row = 0; row < HEIGHT / 8; row++) {
        for (column = 0; column < WIDTH; column += 64) {
            oled_128x64_write(oled, &pages[row][column]);
        }
    }
}

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

    // Create device object
    OLED128x64 oled;
    oled_128x64_create(&oled, UID, &ipcon);

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

    // Clear display
    oled_128x64_clear_display(&oled);

    // Draw rotating line
    gdImagePtr image = gdImageCreate(WIDTH, HEIGHT);
    int black = gdImageColorAllocate(image, 0, 0, 0);
    int white = gdImageColorAllocate(image, 255, 255, 255);
    int origin_x = WIDTH / 2;
    int origin_y = HEIGHT / 2;
    int length = HEIGHT / 2 - 2;
    int angle = 0;

    printf("Press ctrl+c exit\n");

    while (true) {
        double radians = M_PI * angle / 180.0;
        int x = (int)(origin_x + length * cos(radians));
        int y = (int)(origin_y + length * sin(radians));

        gdImageFilledRectangle(image, 0, 0, WIDTH, HEIGHT, black);
        gdImageLine(image, origin_x, origin_y, x, y, white);

        draw_image(&oled, image);
        millisleep(25);

        angle++;
    }

    gdImageDestroy(image);
    ipcon_destroy(&ipcon); // Calls ipcon_disconnect internally
    return 0;
}

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
  • E_STREAM_OUT_OF_SYNC = -12

as defined in ip_connection.h.

All functions listed below are thread-safe.

Basic Functions

void oled_128x64_create(OLED128x64 *oled_128x64, const char *uid, IPConnection *ipcon)

Creates the device object oled_128x64 with the unique device ID uid and adds it to the IPConnection ipcon:

OLED128x64 oled_128x64;
oled_128x64_create(&oled_128x64, "YOUR_DEVICE_UID", &ipcon);

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

void oled_128x64_destroy(OLED128x64 *oled_128x64)

Removes the device object oled_128x64 from its IPConnection and destroys it. The device object cannot be used anymore afterwards.

int oled_128x64_write(OLED128x64 *oled_128x64, uint8_t data[64])

Appends 64 byte of data to the window as set by oled_128x64_new_window().

Each row has a height of 8 pixels which corresponds to one byte of data.

Example: if you call oled_128x64_new_window() with column from 0 to 127 and row from 0 to 7 (the whole display) each call of oled_128x64_write() (red arrow) will write half of a row.

Display pixel order

The LSB (D0) of each data byte is at the top and the MSB (D7) is at the bottom of the row.

The next call of oled_128x64_write() will write the second half of the row and the next two the second row and so on. To fill the whole display you need to call oled_128x64_write() 16 times.

int oled_128x64_new_window(OLED128x64 *oled_128x64, uint8_t column_from, uint8_t column_to, uint8_t row_from, uint8_t row_to)

Sets the window in which you can write with oled_128x64_write(). One row has a height of 8 pixels.

The columns have a range of 0 to 127 and the rows have a range of 0 to 7.

int oled_128x64_clear_display(OLED128x64 *oled_128x64)

Clears the current content of the window as set by oled_128x64_new_window().

int oled_128x64_write_line(OLED128x64 *oled_128x64, uint8_t line, uint8_t position, const char text[26])

Writes text to a specific line (0 to 7) with a specific position (0 to 25). The text can have a maximum of 26 characters.

For example: (1, 10, "Hello") will write Hello in the middle of the second line of the display.

You can draw to the display with oled_128x64_write() and then add text to it afterwards.

The display uses a special 5x7 pixel charset. You can view the characters of the charset in Brick Viewer.

Advanced Functions

int oled_128x64_set_display_configuration(OLED128x64 *oled_128x64, uint8_t contrast, bool invert)

Sets the configuration of the display.

You can set a contrast value from 0 to 255 and you can invert the color (black/white) of the display.

The default values are contrast 143 and inverting off.

int oled_128x64_get_display_configuration(OLED128x64 *oled_128x64, uint8_t *ret_contrast, bool *ret_invert)

Returns the configuration as set by oled_128x64_set_display_configuration().

int oled_128x64_get_api_version(OLED128x64 *oled_128x64, 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 oled_128x64_get_response_expected(OLED128x64 *oled_128x64, 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 oled_128x64_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 oled_128x64_set_response_expected() for the list of function ID defines available for this function.

int oled_128x64_set_response_expected(OLED128x64 *oled_128x64, 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.

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:

  • OLED_128X64_FUNCTION_WRITE = 1
  • OLED_128X64_FUNCTION_NEW_WINDOW = 2
  • OLED_128X64_FUNCTION_CLEAR_DISPLAY = 3
  • OLED_128X64_FUNCTION_SET_DISPLAY_CONFIGURATION = 4
  • OLED_128X64_FUNCTION_WRITE_LINE = 6
int oled_128x64_set_response_expected_all(OLED128x64 *oled_128x64, bool response_expected)

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

int oled_128x64_get_identity(OLED128x64 *oled_128x64, 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.

Constants

OLED_128X64_DEVICE_IDENTIFIER

This constant is used to identify a OLED 128x64 Bricklet.

The oled_128x64_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.

OLED_128X64_DEVICE_DISPLAY_NAME

This constant represents the human readable name of a OLED 128x64 Bricklet.