Controlling WS2812 LEDs

I recycled components from old builds to make this 3-pixel test rig. It will plug into the bottom headers of the Tiva C launchpad using vbus, gnd, and PD0.

I'm thinking of using a TIVA C Launchpad as the first hardware platform to drive these. This has a chip that can run at 40 MHz (using external crystal to drive the PLL).

There are 5 timings for the ws2812S:

• 350ns
• 800ns
• 700ns
• 600ns
• >50us

If I can run a timer with two different compare interrupts I can use the following values:

• 350ns = 14 cyles @ 40 MHz
• 800=32
• 700=28
• 600=24

Interrupt scheme:

• If this is a digital 0: Set compareA to 14 and compareB to (32+14)
• If this is a digital 1: Set compareA to 28 and compareB to (24+28)
• drive pin high
• start counter
• at compareA:
  • drive pin low
• at compareB:
• drive pin high
• look up next bit and set compares accordingly