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Re: weird voltage 3.0V on GPIO.26

Posted: Tue May 17, 2016 1:40 pm
by MarkHaysHarris777
davenull wrote:is what you're talking about still about me TOP questio "weird voltage 3.0V on GPIO.26" ?

if not, please open your own topic, thank you.
I think so, if not, very closely related. Some of the pins are configured on bootup with pullup resistors (there are a couple of options) and I was not aware of that. That might be accounting for the weird voltage on 26; my point for taggin along on this thread is that "I thought" all pins were inputs on boot-up (ehem... there shouldn't be voltage on any of them) but that is not true. Well, I noticed a weird voltage on pin 29 GPIO05 (enough to light a low power LED dimly). Joan says that's normal, due to the pullup resistor on 29 being configured on during bootup; perhaps 26 is the same?

Re: weird voltage 3.0V on GPIO.26

Posted: Tue May 17, 2016 1:46 pm
by davenull
I understand.

The situation was:
GPIOs 21,22,28 are at 3.3V after complete booting,
e.g. 23,24,25 are at 0V after booting as expected.

Now meanwhile it cannot be booted at all any more, so most probably the Pi is broken and the issue is unfortunately sort of resolved.

Re: weird voltage 3.0V on GPIO.26

Posted: Tue May 17, 2016 2:45 pm
by joan
MarkHaysHarris777 wrote: ...
Thanks, Joan. It dawned on me just now, I have been trying to short pin 5 to ground on boot-up to get the recovery login without the shift key/ that maybe its not supposed to be board # pin 5, but GPIO05?

Can you confirm one way or the other... one blog I read said short pin 5 with pin 6, the other said short pin 5 to ground (I really don't want to experiment with it till I know frankly, but I'm suspecting that its GPIO05 with either 6 or ground?? tnx in advance.
I don't know about that.

On the pulls, the default settings are given on page 102 of the Broadcom Peripheral Specification.

Basically at power-up GPIO 0-8 are pulled high, GPIO 28-29 have no pulls, and the rest are pulled low. I'm ignoring GPIO 32-53 which are only accessible on the compute module.