Add twinkle and a few more params and make the display less janky and

more robust.

1 files changed, 53 insertions, 0 deletions

diff --git a/main/pattern/twinkle.c b/main/pattern/twinkle.c
new file mode 100644
index 0000000..d23b111
--- /dev/null
+++ b/main/pattern/twinkle.c
@@ -0,0 +1,53 @@
+#include <stdint.h>
+#include <stdlib.h>
+
+#include "pattern/twinkle.h"
+
+// The shape of a "spike"
+uint8_t w_arr[91] = {1,   2,   4,   7,   11,  17,  24,  33,  44,  56,  70,  85,
+                     101, 117, 134, 151, 167, 183, 197, 210, 222, 232, 240, 247,
+                     251, 254, 255, 255, 253, 250, 246, 240, 234, 227, 219, 211,
+                     202, 194, 185, 176, 167, 158, 149, 140, 132, 123, 116, 108,
+                     101, 94,  87,  81,  75,  69,  64,  59,  54,  50,  46,  42,
+                     39,  35,  32,  30,  27,  25,  22,  20,  18,  17,  15,  14,
+                     12,  11,  10,  9,   8,   7,   6,   6,   5,   4,   4,   3,
+                     3,   3,   2,   2,   2,   1,   1};
+
+static inline uint8_t byte_scale(uint8_t n, uint8_t sc)
+{
+  return n * sc / 255;
+}
+
+static uint8_t calc_w(uint8_t n, uint8_t shift)
+{
+  uint8_t s = byte_scale(shift, 164);
+  uint8_t n_p = byte_scale(n, 255 - s) + s;
+  if (n_p < 164) {
+    return 0;
+  }
+
+  return w_arr[n_p - 164];
+}
+
+/* Produces a "pseudo-random" number given seed 'x' */
+static uint8_t pseudo_random(uint8_t x)
+{
+  return (1103515245 * x + 12345) & 0xFF;  // & 0xFF ensures the result is 0-255
+}
+
+/* Produces a randomize "twinkle" effect. */
+uint8_t twinkle(uint32_t time, size_t x, uint8_t amt)
+{
+  uint8_t time_offset = pseudo_random(x);
+
+  uint32_t adj_time = time - time_offset;
+  uint32_t time8 = adj_time & 0xff;
+  uint32_t speed = pseudo_random((adj_time >> 8) + x) & 0x3;
+
+  time8 *= speed;
+  if (time8 <= 255) {
+    return calc_w(time8, amt);
+  } else {
+    return 0;
+  }
+}