apress/deploy/uno-q/sketches/matrix_effects/matrix_effects.ino

// Matrix animation sampler for the Arduino Uno Q's 13x8 blue LED matrix.
// Cycles through several frame-based effects: rain -> knight-rider sweep ->
// comet -> ripple -> bloom -> breathe -> sparkle -> checker -> wipe, then
// repeats. All monochrome (pixels are on/off;
// the LEDs are physically blue — there is no colour or brightness control).
//
// Shared pattern: each effect fills the 8x13 `grid`, then show() packs it into
// the uint32_t[4] the driver wants and pushes it with loadFrame(). The only
// matrix calls that exist here are begin() and loadFrame().
//
// Compile: arduino-cli compile --fqbn arduino:zephyr:unoq --export-binaries
// Flash:   arduino-flash <sketch>.ino.elf-zsk.bin   (OpenOCD @ 0x80F0000)

#include "Arduino_LED_Matrix.h"

Arduino_LED_Matrix matrix;

static const uint8_t W = 13; // columns
static const uint8_t H = 8;  // rows

bool grid[H][W];
uint32_t frame[4];

void clearGrid() {
  for (uint8_t y = 0; y < H; y++)
    for (uint8_t x = 0; x < W; x++) grid[y][x] = false;
}

// pack grid -> frame (row-major, MSB-first: pixel 0 = frame[0] bit 31) and show
void show(uint16_t ms) {
  frame[0] = frame[1] = frame[2] = frame[3] = 0;
  uint16_t bit = 0;
  for (uint8_t y = 0; y < H; y++)
    for (uint8_t x = 0; x < W; x++) {
      if (grid[y][x]) frame[bit >> 5] |= (1UL << (31 - (bit & 31)));
      bit++;
    }
  matrix.loadFrame(frame);
  delay(ms);
}

// --- digital rain: per-column drops (head + short trail), staggered speeds ---
int8_t  rHead[W];
uint8_t rLen[W], rPer[W], rPh[W];
void rainSeed(uint8_t x) {
  rHead[x] = -(int8_t)random(0, H);
  rLen[x]  = random(2, 5);
  rPer[x]  = random(1, 4);
  rPh[x]   = 0;
}
void rain(uint16_t frames) {
  for (uint8_t x = 0; x < W; x++) rainSeed(x);
  for (uint16_t f = 0; f < frames; f++) {
    clearGrid();
    for (uint8_t x = 0; x < W; x++) {
      for (uint8_t t = 0; t < rLen[x]; t++) {
        int y = rHead[x] - t;
        if (y >= 0 && y < H) grid[y][x] = true;
      }
      if (++rPh[x] >= rPer[x]) {
        rPh[x] = 0;
        rHead[x]++;
        if (rHead[x] - (int8_t)rLen[x] >= (int8_t)H) rainSeed(x);
      }
    }
    show(90);
  }
}

// --- knight-rider: a full-height bar sweeps left<->right with a light trail ---
void knight(uint8_t sweeps) {
  for (uint8_t s = 0; s < sweeps; s++) {
    for (uint8_t dir = 0; dir < 2; dir++) {
      for (int i = 0; i < W; i++) {
        int x = dir ? (W - 1 - i) : i;
        int xt = dir ? x + 1 : x - 1; // trailing column
        clearGrid();
        for (uint8_t y = 0; y < H; y++) {
          grid[y][x] = true;
          if (xt >= 0 && xt < W && (y % 2 == 0)) grid[y][xt] = true;
        }
        show(70);
      }
    }
  }
}

// --- ripple: expanding square outline from the centre ---
void ripple(uint8_t reps) {
  const int cx = 6, cy = 3;
  for (uint8_t r0 = 0; r0 < reps; r0++) {
    for (int r = 0; r < 8; r++) {
      clearGrid();
      for (int y = 0; y < H; y++)
        for (int x = 0; x < W; x++)
          if (max(abs(x - cx), abs(y - cy)) == r) grid[y][x] = true;
      show(110);
    }
  }
}

// --- sparkle: random pixels twinkle ---
void sparkle(uint16_t frames) {
  for (uint16_t f = 0; f < frames; f++) {
    clearGrid();
    for (uint8_t k = 0; k < 10; k++) grid[random(0, H)][random(0, W)] = true;
    show(70);
  }
}

// --- wipe: fill column-by-column, then clear column-by-column ---
void wipe(uint8_t reps) {
  for (uint8_t r = 0; r < reps; r++) {
    for (uint8_t on = 0; on < 2; on++) {
      for (int x = 0; x < W; x++) {
        for (uint8_t y = 0; y < H; y++) grid[y][x] = (on == 0);
        show(45);
      }
    }
  }
}

// --- comet: a pixel bounces around the edges, trailing its last few cells ---
void comet(uint16_t frames) {
  const uint8_t TRAIL = 5;
  int hx[TRAIL], hy[TRAIL];
  int x = random(0, W), y = random(0, H), dx = 1, dy = 1;
  for (uint8_t i = 0; i < TRAIL; i++) { hx[i] = x; hy[i] = y; }
  for (uint16_t f = 0; f < frames; f++) {
    for (int i = TRAIL - 1; i > 0; i--) { hx[i] = hx[i - 1]; hy[i] = hy[i - 1]; }
    hx[0] = x; hy[0] = y;
    clearGrid();
    for (uint8_t i = 0; i < TRAIL; i++) grid[hy[i]][hx[i]] = true;
    show(70);
    x += dx; y += dy;                              // advance, then reflect off walls
    if (x < 0)      { x = 1;     dx = 1;  }
    else if (x > W - 1) { x = W - 2; dx = -1; }
    if (y < 0)      { y = 1;     dy = 1;  }
    else if (y > H - 1) { y = H - 2; dy = -1; }
  }
}

// --- bloom: a filled diamond grows from the centre to full, then collapses ---
void bloom(uint8_t reps) {
  const int cx = 6, cy = 3;
  for (uint8_t r0 = 0; r0 < reps; r0++) {
    for (uint8_t dir = 0; dir < 2; dir++) {
      for (int r = 0; r <= 8; r++) {
        int rad = dir ? (8 - r) : r;
        clearGrid();
        for (int y = 0; y < H; y++)
          for (int x = 0; x < W; x++)
            if (max(abs(x - cx), abs(y - cy)) <= rad) grid[y][x] = true;
        show(80);
      }
    }
  }
}

// --- breathe: a dithered shimmer whose density swells and fades (no true fade,
//     so we ramp how many pixels are lit via a fixed per-pixel threshold) ---
void breathe(uint8_t breaths) {
  static uint8_t thr[H][W];
  for (uint8_t y = 0; y < H; y++)
    for (uint8_t x = 0; x < W; x++) thr[y][x] = random(0, 100);
  for (uint8_t b = 0; b < breaths; b++) {
    for (uint8_t dir = 0; dir < 2; dir++) {
      for (int s = 0; s <= 100; s += 8) {
        int level = dir ? (100 - s) : s;
        clearGrid();
        for (uint8_t y = 0; y < H; y++)
          for (uint8_t x = 0; x < W; x++)
            if (thr[y][x] < level) grid[y][x] = true;
        show(45);
      }
    }
  }
}

// --- checker: a checkerboard that inverts on each beat ---
void checker(uint8_t flips) {
  for (uint8_t p = 0; p < flips; p++) {
    clearGrid();
    for (uint8_t y = 0; y < H; y++)
      for (uint8_t x = 0; x < W; x++)
        if (((x + y + p) & 1) == 0) grid[y][x] = true;
    show(250);
  }
}

void setup() {
  matrix.begin();
  randomSeed(micros());
}

void loop() {
  rain(70);
  knight(2);
  comet(120);
  ripple(2);
  bloom(2);
  breathe(2);
  sparkle(40);
  checker(6);
  wipe(2);
}