Hi All -
I need to control 9 bi-color LEDs as cheaply as possible. Actually, 9 groups of 9 bi-color LEDs, 81 total, but it should be a lot easier to handle them 9 at a time.
I've almost finished a little charlie-plexing design using 5 pins of an attiny12, which leaves 1 pin to communicate with. At $1.72ea from Digikey, this seems to be the cheapest way to go. Much more so than a Maxim LED driver like the 7219 ...
Data would be one-way from the host AVR to the attiny12 only. Really just telling it which LEDs to turn on/off. The attiny will just sit in a loop cycling through the on/off data for the LEDs and twiddling the pins appropriately.
So, I need a simple one-way one-wire protocol. It would have to be timing-based since it's only a single pin. I'm thinking of something similar to the standard TWI/1-wire protocol, but was wondering if anyone had any better ideas, or better yet, implementations ?