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How To: Graphics Library

With more and more types of LCD types supported by TOWER, we have developed a universal graphics library that can be used with many types of displays.

Starting with our LCD Module, SSD1306, ST7735, MAX7219 or even using WS2812B digital LED strip in matrix configuration as a display.

References​

caution

You always have to set the font first before printing any text. Otherwise, nothing is displayed. Not used fonts are removed for optimization.

Example: twr_gfx_set_font(pgfx, &twr_font_ubuntu_13);.

Examples​

info

Every change you make - draw a string or a line, rotate the display, etc is done internally and no changes are visible until you call the twr_gfx_update(pgfx) function.

This is done for low-power reasons.

LCD Module​

info

This is a simple example of printing Hello world to the LCD Module that is available for TOWER Kit.

Using GFX with LCD Module Code Example

#include <application.h>

// Pointer to GFX instance
twr_gfx_t *pgfx;

void application_init(void)
{
    // LCD Module
    twr_module_lcd_init();
    pgfx = twr_module_lcd_get_gfx();

    twr_gfx_set_font(pgfx, &twr_font_ubuntu_13);
    twr_gfx_draw_string(pgfx, 50, 50, "Hello world", true);
    twr_gfx_update(pgfx);
}

SSD1303 OLED​

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This is a similar example to the last one, but here we use the SSD1303 OLED display for printing the string.

Using GFX with SSD1303 OLED Code Example

#include <application.h>

twr_gfx_t gfx;
twr_ssd1306_t ssd1306;
TWR_SSD1306_FRAMEBUFFER(ssd1306_framebuffer, 128, 64)

void application_init(void)
{
    twr_ssd1306_init(&ssd1306, TWR_I2C_I2C0, TWR_SSD1306_ADDRESS_I2C_ADDRESS_DEFAULT, &ssd1306_framebuffer);
    twr_gfx_init(&gfx, &ssd1306, twr_ssd1306_get_driver());

    twr_gfx_set_font(&gfx, &twr_font_ubuntu_13);
    twr_gfx_draw_string(&gfx, 50, 50, "Hello world", true);
    twr_gfx_update(&gfx);
}

Custom GFX Driver​

info

You can also create your driver for some special display that you want to use.

The driver needs to implement at least these 5 functions.

#include <application.h>

twr_gfx_t gfx;
twr_ssd1306_t ssd1306;
TWR_SSD1306_FRAMEBUFFER(ssd1306_framebuffer, 128, 64)

void application_init(void)
{
    twr_ssd1306_init(&ssd1306, TWR_I2C_I2C0, TWR_SSD1306_ADDRESS_I2C_ADDRESS_DEFAULT, &ssd1306_framebuffer);
    twr_gfx_init(&gfx, &ssd1306, twr_ssd1306_get_driver());

    twr_gfx_set_font(&gfx, &twr_font_ubuntu_13);
    twr_gfx_draw_string(&gfx, 50, 50, "Hello world", true);
    twr_gfx_update(&gfx);
}
Custom GFX Driver Implementation Code Example

bool led_matrix_is_ready(void *param)
{
    return true;
}

void led_matrix_clear(void *param)
{
    memset(framebuffer, 0x00, sizeof(framebuffer));
}

void led_matrix_draw_pixel(void *param, uint8_t x, uint8_t y, uint32_t enabled)
{
    uint8_t sub = LED_MODULES_COUNT-1;

    if(enabled)
    {
        framebuffer[(sub - (x / 8)) + (8-y) * LED_MODULES_COUNT] |= 1 << (x % 8);
    }
    else
    {
        framebuffer[(sub - (x / 8)) + (8-y) * LED_MODULES_COUNT] &= ~(1 << (x % 8));
    }
}

twr_gfx_caps_t led_matrix_get_caps(twr_ls013b7dh03_t *self)
{
    (void) self;
    static const twr_gfx_caps_t caps = { .width = 32, .height = 8 };
    return caps;
}

const twr_gfx_driver_t *led_matrix_get_driver(void)
{
    static const twr_gfx_driver_t driver =
    {
        .is_ready = (bool (*)(void *)) led_matrix_is_ready,
        .clear = (void (*)(void *)) led_matrix_clear,
        .draw_pixel = (void (*)(void *, int, int, uint32_t)) led_matrix_draw_pixel,
        .update = (bool (*)(void *)) led_matrix_update,
        .get_caps = (twr_gfx_caps_t (*)(void *)) led_matrix_get_caps
    };

    return &driver;
}