I am trying to create a discrete rgb led matrix, using rgb leds common cathode, using a maxim 7219 or 7221. I intend on using one 7219/7221 for each color. My question is how do I hook up the cathode for the leds, they are common cathode, do I just connect the cathodes to each chip and rely on the anodes to switch the colors (I hope I am being clear enough here). I have a basic understanding of electronics but it has been a while since I have done any circuit design.
Thanks for any help
It's just a simple matrix using the DIG and SEG output pins:
You might want to re-order the row and column outputs to accommodate your project.
the problem I am not able to figure out is the rgb led's have a common cathode and a separate anode for each of the different colors. I intend on using a 7219/7221 for each color, how do I connect the cathode pin for the led, do I need to connect the same cathode pin to each of the 7219/7221s.
I don't think you're going to be able to use the MAX7219; with common cathodes on your LEDs you would need the 7219s to be in sync with each other (so that each was selecting the same DIGx pin at the same time), and I don't know if that's possible.
You might want to look at the schematic of this product for ideas:
-- http://www.sparkfun.com/commerce/product_info.php?products_id=760#