# PixelDust Digital Sand Demos for Arcada ## Overview PyGamer and PyBadge have built in accelerometers - which you can use in your games or demos to make nifty motion-activated effects. In this mini guide we'll show you some examples of [PaintYourDragon's PixelDust](https://github.com/adafruit/Adafruit_PixelDust) library but for Arcada boards https://www.youtube.com/watch?v=GXRP9LKlqnA # Supported Hardware You'll need a board with [Adafruit Arcada](https://github.com/adafruit/Adafruit_Arcada) support + an accelerometer such as... Featured ### Adafruit PyGamer Starter Kit [Adafruit PyGamer Starter Kit](https://www.adafruit.com/product/4277) **Please note: you may get a royal blue _or_ purple case with your starter kit (they're both lovely colors)** What fits in your pocket, is fully Open Source, and can run CircuitPython, MakeCode Arcade or Arduino games you write yourself? That's right,... 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[Then install the Adafruit Arcada libraries](https://learn.adafruit.com/adafruit-pybadge/arcada-libraries) (there's a _lot_ of em!) Also install the [Adafruit PixelDust](https://github.com/adafruit/Adafruit_PixelDust) library ![](https://cdn-learn.adafruit.com/assets/assets/000/076/667/medium800thumb/sensors_ezgif-1-4b7d80e51b58.jpg?1560136205) # Compilation Settings As you get to a few thousand particles, you'll want to speed up your board as much as possible. Compile with _ultra-speed_ settings such as `200MHz overclock`, `-Ofast optimizations` and `Cache enabled`. ![](https://cdn-learn.adafruit.com/assets/assets/000/076/660/medium800/sensors_image.png?1560132947) # Runtime Settings There's not a lot of things you can adjust but here's a few common ones: `#define CHUNKY_SAND` If this is at the top of the code, it will make each particle a 2x2 pixel rather than a single pixel. this makes it look a little better, but you can't fit as many particles on the screen. `#define N_FLAKES 2000` How many particles to simulate. More look cooler but too many and it slows down! 1000-2000 seems to be a good number, especially with `CHUNKY_SAND` turned on. On this line in the loop: `pixeldust->iterate(xx * 3000.0, yy * 3000.0, zz * 3000.0);` The multiplier affects the 'gravity' of the pixels. Larger numbers will drag the pixels down faster, smaller numbers will make the pixels float a little more. # Snow Demo Start with the **pixeldust\_demos-\>pixeldust\_snow** example, its the simplest demo - each pixel is the same white color. ![](https://cdn-learn.adafruit.com/assets/assets/000/076/661/medium800/sensors_image.png?1560133057) Upload and enjoy! ![sensors_snow.jpg](https://cdn-learn.adafruit.com/assets/assets/000/076/662/medium640/sensors_snow.jpg?1560133972) # Sand Demo This demo builds on the snow version to add speckled yellow colors to each particle, to create a sand-effect! ![sensors_sand.jpg](https://cdn-learn.adafruit.com/assets/assets/000/076/665/medium640/sensors_sand.jpg?1560134798) You can add color to each pixel by creating a new array of 16-bit colors as we do in this demo with the creation of `uint16_t *flake_colors;` and then later `flake_colors = (uint16_t *)malloc(N_FLAKES *2)`; Then you can assign the colors, we'll use an HSV picker to find a hue we think is sandy... ![](https://cdn-learn.adafruit.com/assets/assets/000/076/664/medium800/sensors_image.png?1560134535) And randomly assign brightness/saturations so we get a range of sandy colors! ```auto // randomize colors for (int i=0; i< N_FLAKES; i++) { flake_colors[i] = __builtin_bswap16(arcada.ColorHSV565(40, // Hue (sandy) random(50, 100), // saturation random(50, 100))); // brightness } ``` Note we use `__builtin_bswap16` on each color word. That's because we later use DMA to write out all the pixels and we need to have the high/low bytes of color swapped in order for it to run as fast as possible (its a weird effect of TFT DMA on Arduino) Later on, when we draw the pixels, we'll look up the corresponding color before we draw the color to our framebuffer: ```auto for(int i=0; igetPosition(i, &x, &y); //Serial.printf("(%d, %d) -> %d\n", x, y, x * width + y); uint16_t flakeColor = flake_colors[i]; #ifdef CHUNKY_SAND framebuffer[2*y * width + 2*x] = flakeColor; framebuffer[2*y * width + 2*x+1] = flakeColor; framebuffer[(2*y+1) * width + 2*x] = flakeColor; framebuffer[(2*y+1) * width + 2*x + 1] = flakeColor; #else framebuffer[y * width + x] = flakeColor; #endif } ``` # Logo Demo Finally, the most advanced of the demos adds a logo 'obstacle' both as an image and a 'mask' that tells PixelDust where not to let pixels go. This makes for lovely effects as particles slide around. ![](https://cdn-learn.adafruit.com/assets/assets/000/076/666/medium800thumb/sensors_ezgif-1-247db949ce6f.jpg?1560136066) For the logo, which is 8-bit grayscale and stored in the header, [you can use a tool like this that will take an image and convert it into a header file](https://littlevgl.com/image-to-c-array). Like the sand demo we will store a color for each particle. Except this time instead of randomly placing them on the display, they are put into boxes along the bottom of the screen: ```auto // Set up initial sand coordinates, in 8x8 blocks int n = 0; for(int i=0; i (%d, %d)\n", n, xx + x, yy + y); pixeldust->setPosition(n++, xx + x, yy + y); } } } ``` Since the chunks of particle divide up into 8 colors, we dont have to store the color of each one, we know that the index of the particle, divided by 8, gives the color index. Notes we have to `bswap16` the color here like we did before. ```auto colors[0] = arcada.color565(40 , 40, 40); // Dark Gray colors[1] = arcada.color565(120, 79, 23); // Brown colors[2] = arcada.color565(228, 3, 3); // Red colors[3] = arcada.color565(255,140, 0); // Orange colors[4] = arcada.color565(255,237, 0); // Yellow colors[5] = arcada.color565( 0,128, 38); // Green colors[6] = arcada.color565( 0, 77,255); // Blue colors[7] = arcada.color565(117, 7,135); // Purple for (int i=0; i