GPIO 14 does not stay high on power up (Pi Zero W version 1.1) about lipopi HOT 26 CLOSED

Raspbian version 9 (stretch)

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Ok, testing now, but it appears that UART RX stays high when powered up. I will reimplement the power up/down circuit using GPIO 15 and see if it works. The pin is constant at 2.47v which seems enough to keep EN happy.

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Does RX go low again after shutdown though?
If it doesn't the circuit wont work.

Unfortunately they keep messing with the serial port settings and its almost impossible to keep up. I would keep trying different combinations until you find one that makes TX go high. Did you try the enable_uart boot setting?

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It is in the README?
Step2 in the software setup.

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Ahhh sorry, I didn't realise you were looking at the power up/down version, thanks for the tipoff I've updated it.

I had a look at your circuit, I have to say I'm not great at RC networks either and there's a lot going on in that circuit so I couldn't say for sure if it would work but I can't see any harm that could come from trying?

The only possible issue I could see is theoretically there could be infinite current from bat through push button and diode to the capacitor during initial charging of the 4.7u. Its a small enough cap that it likely wont matter though but if you wanted to be really cautious you could put a small resistor, say 100 ohm between bat and the pushbutton just to keep it under control.

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Well, worth a try, but no luck. The 2M (actually 1.8M) is to much resistance to be an effective pull down resistor, and so EN never goes low. Somehow I need a way to isolate the RC network from EN such that it holds it high for the required period without letting the cap prematurely discharge through the 100K pulldown.

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Now I am heading into dangerous territory, as I only have a slight clue as to what I am doing.

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Transistor is the wrong way around I think, should be pointing downwards.

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Whoops, I was disoriented. Yes, upside down. I have the transistors on order, I'll try it out then.

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Another suggestion I received on electronics.stackexchange does the EN pulldown through the UART. Not sure if this would work, but interesting idea:

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Yes that may well work.

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No, don't think so. Powered off, there is 29M resistance between UART Tx and Gnd.

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Yeah that sounds to high for the pulldown to be active, the integrated pull up/down resistors are like 50k I think.

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I have a working solution. Very similar to your original, with the addition of a capacitor and I replaced the two diode voltage step down with a voltage divider - which actually reduced the component count because the 22K also serves the same purpose of the original 10K on GPIO 18.

So, press/release to power on. Capacitor keeps EN high for a bit more than 10 seconds so UART TX can stabilize. Press again to power off. After the Pi shuts down, EN keeps the powerboost on for an additional 8 seconds or so, but not an issue.

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Awesome!
Would you be prepared to do a pull request to include it in the project?

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I have a branch to push for a pull request, but I don't have write access

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Yes thats correct, I can't remember how you do it exactly but I think you commit it to your own repo then make a pull request or something?

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Does this help?
https://help.github.com/articles/creating-a-pull-request/

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Thanks for that!
Sorry it took so long to reply I've had a crazy week.
I'll also add you to the contributors list.

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