raspberry_ws2812

This module contains python routines to program the WS2812 RGB LED chips on the raspberry, using the hardware SPI MOSI (so no other hardware is needed)

As the WS2812 communication needs strict timing, the DIN line cannot be driven from a normal GPIO line with python (an interrupt on the raspberry would screw things up). Thats' why this module uses the hardware SPI MOSI line, this does confirm to the timing requirements.

More info on the WS2812: https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/

Wiring of WS2812-Raspberry

Connections from the Raspberry to the WS2812:

WS2812     Raspbery
GND   --   GND. At least one of pin 6, 9, 14, 20, 25
DIN   --   MOSI, Pin 19, GPIO 10
VCC   --   5V. At least one of pin 2 or 4

Of course the WS2812 can (should) be chained, the DOUT of the first connected to the DIN of the next, and so on.

Setup SPI on Raspberry

First, enable the SPI hardware module on the SPI, using raspi-config, in Advanced Options / SPI, and enabeling the SPI interface and the module loading: sudo raspi-config

Then, get the python spidev module:

git clone https://github.com/doceme/py-spidev.git
cd py-spidev
make
make install

Testing this ws2812.py module

This module can be tested using: python ws2812.py

Sample program that uses the module:

import spidev
import ws2812
spi = spidev.SpiDev()
spi.open(0,0)

#write 4 WS2812's, with the following colors: red, green, blue, yellow
ws2812.write2812(spi, [[10,0,0], [0,10,0], [0,0,10], [10, 10, 0]])

Notes

Note: this module tries to use numpy, if available. Without numpy it still works, but is really slow (more than a second to update 300 LED's on a Raspberry Pi Zero). So, if possible, do:

sudo apt install python-numpy