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I have a working button debounce circuit based on the LMC 555 timer Vcc = 3,3V. It's configured in monostable mode with a positive pulse T = about 0,1 sec. When the 555 is not triggered it's output pin 3 stays LOW. Se attached picture. I have configured Pi with an interrupt, (falling edge ). What concerns me before I connect pin 3 555 to GPIO is if I should worry about how to set the GPIO ports during the initialization:
Does it matter how I set pull up or pull down? Given LOW at pin 3, 555 startuptime?
Code: Select all
GPIO.setup(18, GPIO.IN, pull_up_down=GPIO.PUD_DOWN) or GPIO.setup(18, GPIO.IN, pull_up_down=GPIO.PUD_UP)
- SDS00006.png (13.96 KiB) Viewed 289 times
not really because any pull up or down the output on the cmos 555 will act like a loading resistor to vcc or gnd . The ones internal to the gpio array is 100K btw.