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September 12, 2014 AT 4:07 pm

NeoPixels on Raspberry Pi @Raspberry_Pi #raspberrypi #piday

NeoPixels on Raspberry Pi is a new guide on the learning system:

Wouldn’t it be fun to add bright, beautiful NeoPixels to your Raspberry Pi project?  However NeoPixels, and the WS2811/2812 LEDs that make them up, require a data signal with very specific timing to work correctly.  Because the Raspberry Pi runs a multi-tasking Linux operating system it doesn’t have real-time control over its GPIO pins and can’t easily drive NeoPixels.  Typically a small microcontroller like a Trinket or Teensy can be used to communicate with the Raspberry Pi and generate the NeoPixel data signal.  However thanks to the excellent rpi_ws281x library created by Jeremy Garff, you can now control NeoPixels or WS2811/WS2812 LEDs directly from your Raspberry Pi!

Jeremy’s library solves the real-time control problem by using the PWM and DMA hardware on the Raspberry Pi’s processor.  The PWM (pulse-width modulation) module can generate a signal with a specific duty cycle, for example to drive a servo or dim an LED.  The DMA (direct memory access) module can transfer bytes of memory between parts of the processor without using the CPU.  By using DMA to send a specific sequence of bytes to the PWM module, the NeoPixel data signal can be generated without being interrupted by the Raspberry Pi’s operating system.

NeoPixels on Raspberry Pi Guide


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