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GPIO 12-14 state upon boot

PostPosted: Sat Dec 20, 2014 10:46 am
by mharizanov
Guys,
I am working on a home automation project that will control 3 SSRs attached to GPIOs 12-14, but I am experiencing high initial state of those upon boot for about 300ms. I suspect this is the bootloader setting their state and only when my code is executed after 300ms I can take control. 300ms May not seem much, but if it activates something, it may be enough to do the damage.. I am thinking of adding caps to handle this, any other way using software?

Attaching schematics of the thingie, the transformer isn't a transformer but a 5V power supply in transformer form.

Re: GPIO 12-14 state upon boot

PostPosted: Sat Dec 20, 2014 11:45 am
by martinayotte
Do you means that your SSRs turns on during the Reset process due to GPIOs internal pullups driving them ?
If it is the case, I suggest to drive your SSRs with GPIO Low state, which should not happen during Reset until they are initialized as Output.
Then your software should take that in consideration : 0 means ON and 1 means OFF.

Re: GPIO 12-14 state upon boot

PostPosted: Sat Dec 20, 2014 12:02 pm
by mharizanov
I was thinking that too, but left it as last resort. I was hoping that there would be a way to change that silly default behaviour and keep those pins low during boot..

Re: GPIO 12-14 state upon boot

PostPosted: Sat Dec 20, 2014 9:48 pm
by martinayotte
That is not "last resort" ... I didn't verify myself, but if those GPIOs are held by internal pullups during Reset process, you won't have other choice ...
If so, drive your SSRs with active-low ! there is no shame to do so ... :D