mattg31
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Raspberry pi Run pin wiring

Fri Jul 20, 2018 11:10 pm

I am trying to use the "run" pin on a raspberry pi 3 model B+ to wake the pi from standby, and also reboot it. From what I read online I need to just connect the two pads (run pin, and the one directly beside it). This worked on my Raspberry pi 3 Model B. However, on my model 3 B+ I have the official 7 inch touch screen connected. When I connect the run pin to a pushbutton and pullup resistor, and press the button, the screen goes white very slowly, almost as if I am draining the color out of it. When I release the button the pi will reboot, but I feel like this is not normal.

Can someone look at the attached diagram and let me know if this is the correct way to use the run pin?

Thanks!
Image
https://imagebin.ca/v/49NttoT8hXZg

I should also note, the screen is connected to the pi using the ribbon cable, and using two jumpers wires to connect to the screen 5V and GND to the Pi 5V and GND. The screen works as expected, with the exception of when the button is pressed.
If I quickly press the button, nothing happens. However if I hold the button down, this is when I see the color draining issue...

klricks
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Re: Raspberry pi Run pin wiring

Fri Jul 20, 2018 11:45 pm

mattg31 wrote:
Fri Jul 20, 2018 11:10 pm
..... From what I read online I need to just connect the two pads (run pin, and the one directly beside it)....
That is no longer true for the 3B+.
The RUN pin needs to be grounded to reset the RPi and the pin next to RUN is NOT ground on the 3B+. You need to use one of the ground pins in the GPIO header instead.
Unless specified otherwise my response is based on the latest and fully updated RPiOS Buster w/ Desktop OS.

mattg31
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Re: Raspberry pi Run pin wiring

Sat Jul 21, 2018 12:53 am

Ahh ok, thanks!

So to be clear:
I should connect the run pin to 3.3V via a resistor (10K-ish). Then have another wire that connects the Run pin to GND on the GPIO headers via the pushbutton (pushbutton grounds run pin when pressed)?

Thanks again

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Burngate
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Re: Raspberry pi Run pin wiring

Sat Jul 21, 2018 9:48 am

You don't need the pull-up resistor - one is already provided.

I was going to point you towards the schematic, but can't for the life of me find it, for now.
Nevertheless, when you do find it, towards the middle, R43, with the pin-header just below, and going into the chip on PG2

EDIT: https://www.raspberrypi.org/documentati ... educed.pdf

mattg31
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Re: Raspberry pi Run pin wiring

Sun Aug 05, 2018 11:14 am

Thanks a million!

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Imperf3kt
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Re: Raspberry pi Run pin wiring

Sun Aug 05, 2018 9:24 pm

Try to keep your wiring short as they tend to act like an antennae, and spuriously activate a reboot.
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52:4C:52:42:41

Rose coloured glasses are difficult to see through.

MyNameWolfgangS
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Re: Raspberry pi Run pin wiring

Sat Sep 22, 2018 1:11 pm

Hi,

first of all thanks for the explanation. I found out, that this is exactly my problem: I habe a very long cable from my homeserver pi to my serverroom (aprox. 15m). There is another raspi located which has a potentielfree relais connected. In case of my homeserver is not reacting, I than call the second pi, close the relais and my homeserver pi should reboot. All that is working but: there are circumstances, that reboots the homeserver pi without any need (the relais has not been closed).

As you pointed out, the antennae effect could be the fault. Is there any chance to protect that with resistors and/or campacitors?

Any help welcome.

Thanks Wolfgang

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Imperf3kt
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Re: Raspberry pi Run pin wiring

Mon Sep 24, 2018 1:12 am

Sorry, not something I'm familiar with.
Perhaps try shielding the cable with a few mm of aluminium foil?

You may require a lot of foil.
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Rose coloured glasses are difficult to see through.

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Burngate
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Re: Raspberry pi Run pin wiring

Mon Sep 24, 2018 8:06 am

We don't know either the size of a pulse or its length required to reset the chip, so this is all a bit hand-waving.

Since it's pulled up to 3v3 by a 10k resistor, you could try adding another pull-up resistor, say 1k, again to 3v3. That would mean extra energy would be required by any stray EMF to affect it.

You could try adding a capacitor to ground, which would have a similar effect on the energy.
But what would happen if we slowed the rise-time of the RUN signal? Could we slow it down sufficiently that parts of the chip came out of reset, and couldn't find others that still hadn't done so. A bit like your car's starter motor spinning at full speed before it's engaged with the engine, then ripping its gears up when it does try to engage.

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