• ws2812 test rig

    Mike Szczys12/06/2014 at 22:18 0 comments

    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.

  • Early plans

    Mike Szczys12/06/2014 at 20:37 0 comments

    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
    I will need to account for the overhead of lookup and set.