I am trying to set up a gameshow type system where I have 5 stations each having a monitor and a button. The monitor will show a countdown timer and various animations. My plan is to program the timer, animations, and button control through pygame and put a pi at each station each running it's own pygame script, waiting for the start signal (can be keypress or gpio).
I'm having trouble figuring out how to send that signal simultaneously to all stations. Additionally I need to be able to send a 'self destruct' signal to each station to stop the timer. I can ssh into each station but I don't know how to send keypress/gpio signals through the command line to a running pygame script..
I was thinking of putting a rf receiver on each pi, all at the same wavelength and using a common transmitter, but that seems very hacky and not necessarily so simultaneous.
This ought to work ... but it's purely hypothetical:
Use a parallel circuit to set a pin "high" and "low" - "high" means start the timer; "low" means stop the timer.  The next "high" resets and restarts the timer.
You could use two circuits.  One for start/stop and one for "reset".  You'd probably need some code to not reset while running.
The parallel circuit can be controlled manually (for testing) or automatically (perhaps with a master program?).
Control Multiple Raspberry Pis Remotely / Gameshow Type System