Can't get GPIO0 to work as OUTPUT

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Re: Can't get GPIO0 to work as OUTPUT

By Erik84750
- Mon Jul 02, 2018 11:47 am #76799 Hi McChubby007, used as sinking means connected to 3.3V with pullup. Yet when I use no pullup all outputs do work except the 0, and if pullup is used it starts to oscillate when supposed to be low; I am in the midst of trying to discover its behavior in function of pullups, this story is not ended yet.
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Re: Can't get GPIO0 to work as OUTPUT

By McChubby007
- Mon Jul 02, 2018 2:16 pm #76805
Erik84750 wrote:Hi McChubby007, used as sinking means connected to 3.3V with pullup. Yet when I use no pullup all outputs do work except the 0, and if pullup is used it starts to oscillate when supposed to be low; I am in the midst of trying to discover its behavior in function of pullups, this story is not ended yet.

If you look at the diagram I attached; there is an led connected to GPIO 0, via 470ohm resistor and 3.3v, so that gpio acts as a sink (led cathode connected to gpio 0). The led acts correctly when I set output on or off (set pin LOW and led on, as it is a sink etc). I have never seen ocsillation but then I have not inspected with a scope, but visually the led is observed as either on or off. The diagram I attached is actually from a lesser known dev board that used to be for sale. Beyond that I never investigated, since it did what I wanted.
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Re: Can't get GPIO0 to work as OUTPUT

By McChubby007
- Mon Jul 02, 2018 2:27 pm #76806 For what it's worth, I made some notes on other pins which I consider to have 'special' requirements. They were either observed by me, or I found reference on the internet, some time c.2015 when it was all new. I assume they are still valid and I have attached them in case they are useful.

pinNotes.txt
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Re: Can't get GPIO0 to work as OUTPUT

By Erik84750
- Tue Jul 03, 2018 2:56 am #76828 Solved! A defective component and a design error combined, as well as me not thoroughly analysing fault symptoms. Someone suggested to try the blink example, I altered the program to blink both 0 and 2 (builtin led), and that led to this discovery.
Thank you all for your invaluable assistance!
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