A simple stream protocol for controlling arrays of RGB lights.
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zestyping Merge pull request #44 from fyhertz/conwayfix
Some bug fixes for the Conway's game of life python example.
Latest commit 90c163b Mar 21, 2018



A simple stream protocol for controlling RGB lighting, particularly RGB LEDs. See http://openpixelcontrol.org/ for a spec.

Using this implementation, you can write your own patterns and animations, test them in a simulator, and run them on real RGB light arrays. This repository includes these programs:

  • dummy_client: Sends OPC commands for the RGB values that you type in.

  • dummy_server: Receives OPC commands from a client and prints them out.

  • gl_server (Mac or Linux only): Receives OPC commands from a client and displays the LED pixels in an OpenGL simulator. Takes a "layout file" that specifies the locations of the pixels in a JSON array; each item in the array should be a JSON object of the form {"point": [x, y, z]} where x, y, z are the coordinates of the pixel in space. Click and drag to rotate the 3-D view; hold shift and drag up or down to zoom.

  • tcl_server: Receives OPC commands from a client and uses them to control Total Control Lighting pixels (see http://coolneon.com/) that are connected to the SPI port on a Beaglebone.

  • python/opc.py: A Python client library for connecting and sending pixels.

  • python/color_utils.py: A Python library for manipulating colors.

  • python/raver_plaid.py: An example client that sends rainbow patterns.

To build these programs, run "make" and then look in the bin/ directory.

Quickstart (simulator)

Step 1. If you're using Linux, first get the dependencies you need (Mac users skip to step 2):

apt-get install mesa-common-dev freeglut3-dev

Step 2. Compile and start the GL simulator using the example "Freespace" layout:

bin/gl_server -l layouts/freespace.json

Step 3. In another terminal window, send colors to the simulator:


Quickstart (Beaglebone)

Step 1. Log in to your Beaglebone and add these two lines to the /boot/uEnv.txt file.


Step 2. Type reboot to reboot your Beaglebone. You should now see two files at /dev/spidev1.0 and /dev/spidev2.0.

Step 3. Copy the code to your Beaglebone and compile the server appropriate for your LED chipset; pick one:

make bin/apa102_server   # APA102 (Adafruit "DotStar")
make bin/lpd8806_server  # LPD8806, 21-bit colour
make bin/tcl_server      # P9813 ("Total Control Lighting"), 24-bit colour
make bin/ws2801_server   # WS2801, 24-bit colour

Step 4. Connect the ground, data, and clock wires of your LED strand to the appropriate breakout pins on the Beaglebone. For /dev/spidev1.0, data is P9 pin 18 and clock is P9 pin 22. For /dev/spidev2.0, data is P9 pin 30 and clock is P9 pin 31. Ground is on P9 pin 1. See http://beagleboard.org/Support/bone101/#headers-spi for a nice picture.

Step 5. Connect the power wire of your LED strand either to a separate 5V power source, or to your Beaglebone's power on P9 pin 5; choose one or the other, not both. If you are using USB to power your Beaglebone and also using your Beaglebone to power the LEDs, there will only be enough power to light a small number of LEDs at full brightness at any given moment. If you need to light a lot of LEDs and are adding external power sources to provide more power down the line, use only external power sources and do not connect to the Beaglebone's power pin.

Step 6. Run the server on your Beaglebone, specifying the SPI speed, port number, and device path you want to use. For example, to run the TCL server at 8 MHz (the default SPI speed) on port 7890 (the default port), controlling an LED strand connected to P9 pins 18 and 22:

bin/tcl_server 8 7890 /dev/spidev1.0

Step 7. Run a client on the Beaglebone to make it send data to itself (the default server address is


Step 8. Run a client on your laptop to send data to the Beaglebone (if you're using a USB network connection, the Beaglebone's address is most likely; otherwise substitute the Beaglebone's IP address):