We have a Sand/Pixel Dust demo available for the MatrixPortal that runs in Arduino. Below is the code to run it. The demo is also available as an example in the Arduino Protomatter library.

/* ----------------------------------------------------------------------
"Pixel dust" Protomatter library example. As written, this is
SPECIFICALLY FOR THE ADAFRUIT MATRIXPORTAL M4 with 64x32 pixel matrix.
Change "HEIGHT" below for 64x64 matrix. Could also be adapted to other
Protomatter-capable boards with an attached LIS3DH accelerometer.

PLEASE SEE THE "simple" EXAMPLE FOR AN INTRODUCTORY SKETCH,
or "doublebuffer" for animation basics.
------------------------------------------------------------------------- */

#include <Wire.h>                 // For I2C communication
#include <Adafruit_LIS3DH.h>      // For accelerometer
#include <Adafruit_PixelDust.h>   // For sand simulation
#include <Adafruit_Protomatter.h> // For RGB matrix

#define HEIGHT  32 // Matrix height (pixels) - SET TO 64 FOR 64x64 MATRIX!
#define WIDTH   64 // Matrix width (pixels)
#define MAX_FPS 45 // Maximum redraw rate, frames/second

#if HEIGHT == 64 // 64-pixel tall matrices have 5 address lines:
uint8_t addrPins[] = {17, 18, 19, 20, 21};
#else            // 32-pixel tall matrices have 4 address lines:
uint8_t addrPins[] = {17, 18, 19, 20};
#endif

// Remaining pins are the same for all matrix sizes. These values
// are for MatrixPortal M4. See "simple" example for other boards.
uint8_t rgbPins[]  = {7, 8, 9, 10, 11, 12};
uint8_t clockPin   = 14;
uint8_t latchPin   = 15;
uint8_t oePin      = 16;

Adafruit_Protomatter matrix(
  WIDTH, 4, 1, rgbPins, sizeof(addrPins), addrPins,
  clockPin, latchPin, oePin, true);

Adafruit_LIS3DH accel = Adafruit_LIS3DH();

#define N_COLORS   8
#define BOX_HEIGHT 8
#define N_GRAINS (BOX_HEIGHT*N_COLORS*8)
uint16_t colors[N_COLORS];

Adafruit_PixelDust sand(WIDTH, HEIGHT, N_GRAINS, 1, 128, false);

uint32_t prevTime = 0; // Used for frames-per-second throttle

// SETUP - RUNS ONCE AT PROGRAM START --------------------------------------

void err(int x) {
  uint8_t i;
  pinMode(LED_BUILTIN, OUTPUT);       // Using onboard LED
  for(i=1;;i++) {                     // Loop forever...
    digitalWrite(LED_BUILTIN, i & 1); // LED on/off blink to alert user
    delay(x);
  }
}

void setup(void) {
  Serial.begin(115200);
  //while (!Serial) delay(10);

  ProtomatterStatus status = matrix.begin();
  Serial.printf("Protomatter begin() status: %d\n", status);

  if (!sand.begin()) {
    Serial.println("Couldn't start sand");
    err(1000); // Slow blink = malloc error
  }

  if (!accel.begin(0x19)) {
    Serial.println("Couldn't find accelerometer");
    err(250);  // Fast bink = I2C error
  }
  accel.setRange(LIS3DH_RANGE_4_G);   // 2, 4, 8 or 16 G!

  //sand.randomize(); // Initialize random sand positions

  // Set up initial sand coordinates, in 8x8 blocks
  int n = 0;
  for(int i=0; i<N_COLORS; i++) {
    int xx = i * WIDTH / N_COLORS;
    int yy =  HEIGHT - BOX_HEIGHT;
    for(int y=0; y<BOX_HEIGHT; y++) {
      for(int x=0; x < WIDTH / N_COLORS; x++) {
        //Serial.printf("#%d -> (%d, %d)\n", n,  xx + x, yy + y);
        sand.setPosition(n++, xx + x, yy + y);
      }
    }
  }
  Serial.printf("%d total pixels\n", n);

  colors[0] = matrix.color565(64, 64, 64);  // Dark Gray
  colors[1] = matrix.color565(120, 79, 23); // Brown
  colors[2] = matrix.color565(228,  3,  3); // Red
  colors[3] = matrix.color565(255,140,  0); // Orange
  colors[4] = matrix.color565(255,237,  0); // Yellow
  colors[5] = matrix.color565(  0,128, 38); // Green
  colors[6] = matrix.color565(  0, 77,255); // Blue
  colors[7] = matrix.color565(117,  7,135); // Purple
}

// MAIN LOOP - RUNS ONCE PER FRAME OF ANIMATION ----------------------------

void loop() {
  // Limit the animation frame rate to MAX_FPS.  Because the subsequent sand
  // calculations are non-deterministic (don't always take the same amount
  // of time, depending on their current states), this helps ensure that
  // things like gravity appear constant in the simulation.
  uint32_t t;
  while(((t = micros()) - prevTime) < (1000000L / MAX_FPS));
  prevTime = t;

  // Read accelerometer...
  sensors_event_t event;
  accel.getEvent(&event);
  //Serial.printf("(%0.1f, %0.1f, %0.1f)\n", event.acceleration.x, event.acceleration.y, event.acceleration.z);

  double xx, yy, zz;
  xx = event.acceleration.x * 1000;
  yy = event.acceleration.y * 1000;
  zz = event.acceleration.z * 1000;

  // Run one frame of the simulation
  sand.iterate(xx, yy, zz);

  //sand.iterate(-accel.y, accel.x, accel.z);

  // Update pixel data in LED driver
  dimension_t x, y;
  matrix.fillScreen(0x0);
  for(int i=0; i<N_GRAINS ; i++) {
    sand.getPosition(i, &x, &y);
    int n = i / ((WIDTH / N_COLORS) * BOX_HEIGHT); // Color index
    uint16_t flakeColor = colors[n];
    matrix.drawPixel(x, y, flakeColor);
    //Serial.printf("(%d, %d)\n", x, y);
  }
  matrix.show(); // Copy data to matrix buffers
}

This sketch was written for a 64x32 pixel matrix but is easily modified for a 64x64 matrix!

Look for this line in the code:

#define HEIGHT  32 // Matrix height (pixels) - SET TO 64 FOR 64x64 MATRIX!

and change it to:

#define HEIGHT  64 // Matrix height (pixels) - SET TO 64 FOR 64x64 MATRIX!

Now upload the sketch to your MatrixPortal M4. You may need to press the Reset button to reset the MatrixPortal. You should see a a series of colored rectangles along the bottom. Go ahead and start moving the matrix around!

If you have a 3D Printer, be sure to check out the Matrix Portal Sand Handles guide.

This guide was first published on Sep 28, 2020. It was last updated on 2021-03-17 13:45:19 -0400.

This page (Arduino Sand Demo) was last updated on Dec 01, 2021.

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