I'm looking to connect an 8-relay board to an Arduino Uno. A board like this one. However, I don't really want to use up 8 digital outputs if I don't have to. Is there some intermediate circuitry I can either buy or build that would do this?
For example, can I connect something to the serial so that sending '3' would result in binary 00000011 and thus turn on relay's 1 and 2?
Alternately, and probably more lazy, is there an extension board that would just give me a pile more digital pins?