I thought about it some more. The terminal would be capturing keystrokes. I could have a program capturing those keystrokes and sending signals to the interval program, but that seems messy. It would probably be better/easier to implement a scanning keyboard on 8 of the unused GPIO. I can have a separate thread monitor the keys within the interval program. Then a flag can be set for timing_loop() to poll for. A buzzer would probably be nice to provide feedback on a valid entry too. Does that seem simple enough or am I overlooking something?