LCD

This API provides functions to interact with the LCD and VRAM, allowing direct memory access, getter/setter methods, and palette-based drawing.

Changes to VRAM are not automatically rendered on the LCD and must be explicitly refreshed using LCD_Refresh.

Available methods are:

• LCD_ClearScreen: Clears the screen by filling VRAM with white.
• LCD_GetPixel: Retrieves the color of a pixel from VRAM.
• LCD_GetSize: Retrieves the dimensions of the LCD.
• LCD_GetVRAMAddress: Returns a pointer to the VRAM.
• LCD_Refresh: Pushes the content of the VRAM to the LCD.
• LCD_SetPixel: Sets the color of a pixel in VRAM.
• LCD_SetPixelFromPalette: Sets the color of a pixel using a predefined palette.
• LCD_VRAMBackup: Backs up the current contents of VRAM.
• LCD_VRAMRestore: Restores the backed-up contents of VRAM.

Palette Colors

The following colors can be used with LCD_SetPixelFromPalette:

const uint8_t PALETTE_BLACK = 0;
const uint8_t PALETTE_BLUE = 1;
const uint8_t PALETTE_GREEN = 2;
const uint8_t PALETTE_CYAN = 3;
const uint8_t PALETTE_RED = 4;
const uint8_t PALETTE_MAGENTA = 5;
const uint8_t PALETTE_YELLOW = 6;
const uint8_t PALETTE_WHITE = 7;

RGB565 Color Conversion Macros

• RGB_TO_RGB565: Converts RGB values to RGB565 format.
• RGB565_TO_R: Extracts the red component from an RGB565 value.
• RGB565_TO_G: Extracts the green component from an RGB565 value.
• RGB565_TO_B: Extracts the blue component from an RGB565 value.

Methods

Clear Screen

extern "C"
void LCD_ClearScreen();

Clears the LCD by filling VRAM with white.

Get Pixel

extern "C"
uint16_t LCD_GetPixel(int x, int y);

Returns the color of a pixel in VRAM.

• Parameters:
  • x, y: Coordinates of the pixel.
• Returns: The color of the pixel in RGB565 format.

Get LCD Size

extern "C"
void LCD_GetSize(int *width, int *height);

Retrieves the size of the LCD.

• Parameters:
  • width, height: Pointers to store the dimensions of the LCD.

Get VRAM Address

Returns a pointer to the VRAM.

extern "C"
uint16_t *LCD_GetVRAMAddress();

Refresh LCD

Pushes the content of the VRAM to the LCD.

extern "C"
void LCD_Refresh();

Call this after doing any Debug_Printf or drawing on screen to view the changes.

Set Pixel

Sets the color of a pixel in VRAM.

extern "C"
void LCD_SetPixel(int x, int y, uint16_t color);

• Parameters:
  • x, y: Coordinates of the pixel.
  • color: The color to set in RGB565 format.

Set Pixel (From Palette)

Sets the color of a pixel using a predefined palette.

extern "C"
void LCD_SetPixelFromPalette(int x, int y, uint8_t index);

• Parameters:
  • x, y: Coordinates of the pixel.
  • index: Index of the color in the palette.

VRAM Backup

Backs up the current contents of VRAM.

extern "C"
void LCD_VRAMBackup();

VRAM Restore

Restores the backed-up contents of VRAM.

extern "C"
void LCD_VRAMRestore();

Usage

Drawing a purple rectangle

The following code draws a 30x50 Rectangle at (10, 20) in Purple

#include <sdk/os/lcd.hpp>

void example_draw_rectangle() {
    uint16_t *vram = LCD_GetVRAMAddress();
    int width, height;
    LCD_GetSize(&width, &height);

    for (int y = 0; y < 50; ++y) {
        for (int x = 0; x < 30; ++x) {
            vram[(x + 10) + (y + 20) * width] = RGB_TO_RGB565(0xFF, 0x00, 0xFF);
        }
    }

    // Put our changes on the display
    LCD_Refresh();
}

// call example_draw_rectangle in your main

Random Pixel Changes

#include <sdk/os/lcd.hpp>

static uint32_t seed = 12345; // You can change this seed to any value

int rand() {
    seed = (1103515245 * seed + 12345) & 0x7fffffff;
    return seed;
}

void random_pixels() {
    uint16_t *vram = LCD_GetVRAMAddress();
    int width, height;
    LCD_GetSize(&width, &height);

    for (int y = 0; y < 20; ++y) {
        for (int x = 0; x < width; ++x) {
            vram[(x) + (y)*width] =
                RGB_TO_RGB565(my_rand() % 32, my_rand() % 64, my_rand() % 32);
        }
    }

    // Put our changes on the display
    LCD_Refresh();
}