On May 23, 2004, at 3:35 PM, Dave Tweed wrote:
>
> No, that's a competing product. Ours is much larger.

I would love to see some demo pics when you get it running. :-) Can I
ask what you use for your LED array? I've been using Nichia 5mm LEDs,
but they are expensive, large, and hard to find.


> There are a couple of reasons for using a dsPIC, including the very
> high
> instruction rate, and the single-cycle multiply comes in handy for
> things
> like the servo algorithm that keeps the raster spacing locked to the
> period
> of the rotation.
>
> Also, we use scalable vector fonts that are rendered in the ball
> itself,
> which requires a significant amount of computing horsepower.

Ahh, very cool.


> We currently have 6-bit color, with the possibility of going much
> higher
> if we develop a custom LED driver chip.

Do you use PWM or a 2-bit io/resistor DAC for each element?
I am currently using PWM for 12-bit color. I have been able to get
twelve channel ~10khz 4-bit PWM running on a 20mhz PIC, which is just
fine for 4 LEDs at low rpm.

- Ben

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