if you just want to turn on one or two buttons at the same time you could use two 4051 as a matrix like on the right sketch at http://www.arduino.cc/playground/Learning/4051
, so you can conntect up to 64 buttons,
otherwise you could use as well two 4051 connect them to the same 3 digitalOut Pins(so they will get the same adresse all the time) and each of the Outputs comming from the 4051s to one digitalIn Pin, so you just using 5 pin to read 16 puschbuttons,...
ortherwise you could as well do it like the left example at http://www.arduino.cc/playground/Learning/4051, but just connectionthe ouput of the 4051 to a digital Pin not to an analog pin, and so again 64 pushbuttons to read with just 7 digital Pins
so at all the 4051 don't care about if you want to read digital Singals or Analog singals. So never mind and just use the 4051.
ha det bra