Plain C AVR library for ST7735 displays
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#include "st7735_gfx.h"
#include<stdlib.h>
#include "st7735.h"
#define _swap_uint8_t(a, b) { uint8_t t = a; a = b; b = t; }
void st7735_draw_line(uint8_t x0, uint8_t y0, uint8_t x1, uint8_t y1, uint16_t color) {
uint8_t steep_dir = abs(y1 - y0) > abs(x1 - x0);
if (steep_dir) {
_swap_uint8_t(x0, y0);
_swap_uint8_t(x1, y1);
}
if (x0 > x1) {
_swap_uint8_t(x0, x1);
_swap_uint8_t(y0, y1);
}
int16_t dx, dy;
dx = x1 - x0;
dy = abs(y1 - y0);
int16_t err = dx / 2;
int16_t y_step;
if (y0 < y1) {
y_step = 1;
} else {
y_step = -1;
}
uint8_t seg = x0;
uint8_t cur_x;
for(cur_x = x0; cur_x <= x1; cur_x++) {
err -= dy;
if (err < 0) {
if (steep_dir) {
st7735_draw_fast_vline(y0, seg, cur_x - seg + 1, color);
} else {
st7735_draw_fast_hline(seg, y0, cur_x - seg +1, color);
}
y0 += y_step;
err += dx;
seg = cur_x + 1;
}
}
// x0 incremented
if (steep_dir) {
st7735_draw_fast_vline(y0, seg, cur_x - seg, color);
} else {
st7735_draw_fast_hline(seg, y0, cur_x - seg, color);
}
}
void st7735_draw_rect(uint8_t x, uint8_t y, uint8_t w, uint8_t h, uint16_t color) {
if(w < 1 || h < 1) {
return;
}
st7735_draw_fast_hline(x, y, w, color);
st7735_draw_fast_hline(x, y + h - 1, w, color);
st7735_draw_fast_vline(x, y, h, color);
st7735_draw_fast_vline(x + w - 1, y, h, color);
}
void st7735_draw_circle(uint8_t x0, uint8_t y0, uint8_t r, uint16_t color) {
int16_t f = 1 - r;
int16_t ddF_x = 1;
int16_t ddF_y = -2 * r;
int16_t x = 0;
int16_t y = r;
st7735_draw_pixel(x0, y0 + r, color);
st7735_draw_pixel(x0, y0 - r, color);
st7735_draw_pixel(x0 + r, y0, color);
st7735_draw_pixel(x0 - r, y0, color);
while (x<y) {
if (f >= 0) {
y--;
ddF_y += 2;
f += ddF_y;
}
x++;
ddF_x += 2;
f += ddF_x;
st7735_draw_pixel(x0 + x, y0 + y, color);
st7735_draw_pixel(x0 - x, y0 + y, color);
st7735_draw_pixel(x0 + x, y0 - y, color);
st7735_draw_pixel(x0 - x, y0 - y, color);
st7735_draw_pixel(x0 + y, y0 + x, color);
st7735_draw_pixel(x0 - y, y0 + x, color);
st7735_draw_pixel(x0 + y, y0 - x, color);
st7735_draw_pixel(x0 - y, y0 - x, color);
}
}