Sparkfun just released these really nice looking seven segment displays:
Here is the datasheet:
I'm a little confused on how to wire these up to the MAX7221. Whats confusing is all 4 digits shar the same anodes and only differ by the cathodes.
So assuming I need 4 rows (4 digits). Are all the SEG lines connected for the 4 rows and the only difference is the DIG lines which are connected to the anodes. Like this?:
Posting from memory here, but I think . . .
You should be able to do it with 2 MAX7221s if you want to go that route. If you look at this Playground article . . .
. . . you will see that the method is based off a Maxium Application note - Mixed-signal and digital signal processing ICs | Analog Devices which shows (if I remember correctly) a similar situation.
In short, if what you have equates to something <= an RG 8X8 Common Cathode matrix, the multiplexing of 2 MAX7221s will work great. I've used it for a lot of my projects and I really like the "send and forget" ability and the ease of the LedControl lib. Of course it does use the unfashionable MAX7221. [/edit]
Do i really need 2? I can't figure out how to wire two drivers. What part of my (poor) schematic is wrong?
I'm getting confused
Sorry I helped confuse you. I was thinking of something else entirely. Yes, 1 MAX should do it. 5 digits, 8 segments. The MAX sinks 1 digit at a time. http://www.arduino.cc/playground/Main/LedControl