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Problem: GPIO button false trigger on startup
#9
@waffle

POST EDIT: I didn't see the response from @gbh_uk until after I posted. For sure take care of his observations first.

For sure, intermittent bugs are the worst. One my first jobs as an electronically minded teenager was to sit and watch several TV sets in the back room of a local repair shop in hopes of catching them when they misbehaved. That way the real tech could concentrate on repairing sets he'd already diagnosed. He got an extra pair of eyes on the cheap and I got to play with real testing equipment that I would never have been able to access otherwise.

Sorry, I overlooked the bit about this happening specifically when you start the Python script. 

The bit about occasional reboots in your prior work seems pretty conclusive about the script being the culprit, while a 1nf capacitor is too small to cause worry about a possible RC-time constant effect in this applicatoin.

I forgot to ask. Just for completeness, what model RPi and, if an RPi4B, have you tried the same with an earlier model? The Model 4 is a different beast internally but I'm not sure this would matter in your application [Compare https://elinux.org/RPi_BCM2835_GPIOs and https://elinux.org/RPi_BCM2711_GPIOs]

RPi.GPIO V0.7.0 supposedly dealt with two relevant issues: 1) Updated RPI_INFO to include RPi 4B and 2) Fixed pull up/down for Pi4 (issue 168).

Since GPIO 3 is pulled high internally I'm not sure how it might be in the "wrong state" when you start the script but I'll have to think about this some more.

Regards,
Kent
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Messages In This Thread
GPIO button false trigger on startup - by waffle - 06-24-2020, 04:21 PM
RE: GPIO button false trigger on startup - by TheOldPresbyope - 06-25-2020, 01:08 AM

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