neilneil2000
Posts: 25
Joined: Sun Sep 24, 2017 1:38 pm

gpio-poweroff 100ms cycle on shutdown

Mon Oct 02, 2017 1:19 pm

Hi,

I have set up the gpio-poweroff overlay on my Raspberry Pi Zero W but when I shutdown (either -h or -P) rather than a straight transition to logic high, there seems to be a single 5Hz cycle. It is repeatable.

I am wondering if:
- this is the same on all models of RaspberryPi?
- this is expected bahaviour?
- if expected, is this desired behaviour or the result of a limitation?
gpio-poweroff.jpg
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PhilE
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1417
Joined: Mon Sep 29, 2014 1:07 pm
Location: Cambridge

Re: gpio-poweroff 100ms cycle on shutdown

Mon Oct 02, 2017 1:30 pm

gpio-poweroff is a pure software module that only talks to hardware via other drivers. As such (and excluding a patch to allow it to override an exists power-off vector) it is completely cross-platform.

The 100ms pulse before the sustained activate signal is by design - the driver sets the pin on, waits for 100ms, then off, waiting for another 100ms, then high again. However, I couldn't find an explanation for why this might be desirable.

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