This folder contains demos of the BeagleBone's PRU (Programable Real-time Unit) The PRUs have 32-bit cores which run independently of the ARM processor, therefore they can be programmed to respond quickly to inputs and produce very precisely timed outputs.
There are many projects that use the PRU (http://processors.wiki.ti.com/index.php/PRU_Projects) to do things that can’t be done with just a SBC or just a microcontroller.
Here we demonstrate:
blinkInternalLED.c // Blink some of the built in USR LEDs
blinkExternalLED.c // Wire an external LED and blink it
blinkR31.c // Blink an external LED using a faster (50MHz) method
neopixelStatic.c // Wire up NeoPixel (WS2812) LEDs and set them to a color
neopixelDynamic.c // Same LEDs, but a moving display
neopixelRpmsg.c // Control the NeoPixels from the ARM using rpmsg for message passing
neopixelRainbox.py // Runs on the ARM and writes a rainbow pattern to the PRU
inputR31.c // Reads an input pin via the fast R31 register
bitflip.c // Shows how to share memory between the ARM and the PRU
shared.c // Shows how to share memory between the ARM and the PRU
ring.c // Does the "Ring Test" to see how quickly I/O can be toggled
The AI has four PRUs, pru1_0, pru1_1, pru2_0 and pru2_1.
The filename tells which PRU to run on. For example blinkInternalLED.pru1_1.c will run on pru1_1. These demos must all run on pru1_1, except blinkInternalLED, which can run on any of the PRUs.