src/patterns/twinkle.c


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#include <stdio.h>
#include "byte_math.h"
#include "pattern.h"

static uint8_t pseudo_random(uint8_t x) {
    return (1103515245 * x + 12345) & 0xFF; // & 0xFF ensures the result is 0-255
}


static rgb_t get_rgb(uint32_t time, size_t x)
{
  int r = 0, g = 0, b = 0;

  uint8_t time8 = time & 0xff;
  uint8_t time_offset = pseudo_random(x);

  uint32_t adjusted_time = time - time_offset;

  // The random number for this "metaframe." The metaframe is enough to show 1
  // flash. It's used to keep the same LED's from consistently repeating.
  uint32_t metaframe = adjusted_time >> 8;
  uint8_t rand = pseudo_random(x + metaframe);
  uint8_t speed = pseudo_random(rand) % 16;
  uint8_t off = pseudo_random(rand + speed);

  if (speed > 4) {
    speed = 0;
  }

  uint32_t w_index = ((adjusted_time - off) * speed) & 0xff;
  int w = 0;
  if (w_index < 255) {
    w = calc_w(w_index);
  }


  r = 0xff;
  g = byte_scale(byte_sin(time8 + x * 2), 0x60);
  b = 0;

  rgb_t color;
  color.color = 0;
  color.r = clip(r + w);
  color.g = clip(byte_scale(g, AS_BYTE(0.75)) + w);
  color.b = clip(byte_scale(b, AS_BYTE(0.75)) + w);
  return color;
}

static void reset(void)
{
}

__attribute__((__section__(".patterns"))) volatile static pattern_t pat =
    ((pattern_t){.get_rgb = get_rgb, .name = "Twinkle", .reset = reset});