Help Needed with 7219 and 8x8x2 Leds

I am building a large 8x8 matrix of pvc pipe sections (circles) with 2 leds inside each circle. Each led has + and -.

Eventually I want it to play games like only on a bigger scale.

I am hoping to get 3 colors (green,red and both(yellow)) and am
wondering if I should wire the cathodes in common and daisy chain the 7219 or if I should just wire them (and the 2 7219s) totally separately and use more arduino pins.

If I do the latter, will I have to worry about multiplexing “in sync” betwwen the two colors, or will my eyes just see yellow when both leds in a circle are on?

eg: supposing I have the entire matrix green, and also light 2 red leds. Will the 2 leds get updated more often than the greens and therefore end up looking more red in that pvc, or will everything work out and those 2 spots will be yellow?


will I have to worry about multiplexing "in sync" betwwen the two colors,

No the eye will integrate them. The only effect you will see is if you rapidly move the board the after image will look like separate RGB dots and not the mixed coloured dots.

should wire the cathodes in common and daisy chain the 7219

That's what I would do I can't see much advantage in doing anything else.

This is what I did for 2 colors with the MAX7221 . . .

It works great, but I never tried 3 colors. Some others have, but I've never been sure they were successful.

Ok, I ended up wiring the cathodes separate although in retrospect is was more work for nothing. But I will daisy chain the 7219s.

It's looking pretty cool, I'll put up video when done.


I will be doing the same project with RGB leds after this one, so I will get a chance to wire it correctly ;-)