pixel-matrix

1. Connect an LED matrix to your Arduino/Genuino
2. npm install
3. Run TOPIC=<topic> npm start
4. Watch as your matrix dances

Deets

Connect an LED matrix to your Arduino

I used one of these cheap ones from eBay. It has an MAX7219 chip and works over SPI.

I kind of followed these Johnny Five instructions but with different pins on the Uno.

Matrix	Uno
VCC	5V
GND	GND
DIN	11
CS	10
CLK	11

Connect an LED matrix to your Pi

Pin diagram here and here.

Matrix	Fn	Pin num	Name
VCC	5V	4	5v power
GND	GND	6	Ground
DIN	SPI1 MOSI	38	GPIO20
CS	SPI1 CE2	36	GPIO16
CLK	SPI1 SCLK	40	GPIO21

Pick a topic and run it

The node process listens on the MQTT topic specified by the TOPIC environment variable. It falls back to the random andrewn/game-of-life/state topic if none is given.

http://gameoflife.surge.sh is publishing to this topic.

On a Pi, you also need to:

npm install raspi-io

And add the PLATFORM=pi flag to npm start like this:

 sudo TOPIC=<topic> PLATFORM=pi npm start

You can autorun on boot:

 sudo cp pixel-matrix.service /etc/systemd/system/
 sudo systemctl enable pixel-matrix

Data format

Your topic must supply a JSON-encode multi-dimensional array representing each pixel in the matrix.

For example, this will draw a heart:

image = JSON.stringify(
  [
    "01100110",
    "10011001",
    "10000001",
    "10000001",
    "01000010",
    "00100100",
    "00011000",
    "00000000"
  ]
);