Safe way to limit GPIO output time

Question

I'm trying to figure out a fail-safe way to provide an output on GPIO pin of the Pi that would not be vulnerable to my (possibly) buggy code crashes. Is there a surefire way to do so?

Scenario: I need to put GPIO pin to HIGH for up to 30 seconds, while I observe sensor data to make a determination of what happens. If I observe desired conditions are met earlier, I need to pull pin LOW. But if my code crashes, I don't want the pin to remain HIGH for an hour or a day while I figure out that my code crashed.

Short of building a separate circuit (something like 555 timer), is there a way to do this with SoC instructions that would continue in a case of a crash?

PS: Just to clarify, the kind of crash I'm talking about is not Raspberry Pi crash, it's my application crash. Pi will continue idling, while my python process terminates unexpectedly.

Answer 1

pigpio will probably let you do what you want using waves.

The following command line example uses pigs to set GPIO 4 high for 7 seconds.

pigs m 4 w                    # set GPIO 4 to mode output
pigs wvag 16 0 7000000 0 16 0 # wave to switch GPIO 4 high for 7 seconds, then off
pigs wvcre                    # create wave (should return wave 0)

pigs wvtx 0                   # transmit wave 0

You can do the same using the pigpio Python module. Even if the script crashes the GPIO will be switched off at the conclusion of the wave.