Maybe somebody knows...
I 'm working on a project where I use 6 arduinos with 6 oleds independently (some sort of gauges). And my problem is that I need buttons for changing the informations on display. Could I somehow use 2 buttons for 6 arduinos? For example I have 3 buttons 1-next, 2- prev, 3- to switch to another arduino. So I do not need 2 buttons for every arduino (2x6=12 
) I'm using this 2 buttons to each arduino and 3-rd to change between arduinos. Is it possible?
Ah, this is where it gets interesting - you really need some way of cooperating between
the 6 units, which suggests some sort of network.
However things can rapidly get complicated for general networking, so I'd suggest a
simpler way, a chain of serial links.
Have the buttons connected to the "master" Arduino, which interprets the pushs and
maintains the state (a number from 1 to 6 perhaps). Connect its TX pin to the RX of
the next unit, and send that number via serial when it changes. The next Arduino unit
reads the serial line and uses the number to determine what to do and sends the
number to the next unit. Chaining this way allows every slave unit to be programmed
the same as it can simply subtract one from the number before passing it on and listen
only to the number 1.
Or you can common up the line and have the master send to all the others in parallel,
but then the others must be different at least to the extent of knowing which number
they are.
Other ways are for the slaves to be directly controlled by a signal line that's a boolean,
on/off signal, but then the master needs enough outputs to drive 5 others....
It seems to me that I2C would be easier to implement for this. Have the buttons connected to the master and have a button or two to select the address of the slave to send data to. If using Serial you would need to embed the address into the data stream.
I2C does embed the address! And here the address is the data!
Serial is the simplest way.
Designate a 'master' Arduino, all the others are slaves.
Connect the TX pin of the master Arduino to the RX pin of all the others. The master broadcast the button state and 'active slave' over the serial port.
Sorry. I was assuming 2 way communication.