Setting a GPIO port for an accurate time duration with Python

Question

I am trying to set a GPIO port to LOW for n seconds and set it to HIGH afterwards.

The problem is that it's not at all accurate. It varies between a small number of seconds to 2*n or even more.

GPIO.setup(7, GPIO.OUT)
GPIO.output(7, GPIO.LOW)
time.sleep(n)
GPIO.output(7, GPIO.HIGH)

I understand that I can't expect a highly accurate interval but a random number is still weird.

joan · Accepted Answer · 2020-04-22 15:23:05Z

The code you have should be fine.

I'd expect the resulting sleep to be within 1% of n the majority of the time (getting more accurate for larger values of n).

If you are seeing 2 times n it suggests something like:

your system is exceptionally busy
or the circuit you are driving has a large amount of capacitance to overcome
or some other program is affecting the outcome. E.g. if you are using GPIO 4 (pin 7) the 1-wire bus may be enabled.

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