I'm trying to use the minipro powered from a Lipo battery via 3.3V regulator to the 3.3V pin. I recently bought 4 boards from 2 different sources and they look identical. First one worked fine but the second wouldn't run when loaded with the same code. I went back and loaded both with the simple blink code and both run when plugged in to USB, ie driven from 5V, but one won't run from 3.3V supply.
Some sources say the 3.3V pin is output only but others that it casn be used as a supply pin.
No I hadn't seen that thanks. I've just been experimenting and discovered that the "dodgy" chip doesn't even work from 5V - as this note states.
Thats a pain if I have to bypass this diode but then it doesn't work from USB! The note isn't really clear. If I bypass the diode does it disable USB power so I can't reprogram ? If I bypass will it work from 3.3V ?
I'm not to sure what the problem was and how shorting the diode fixed it.
Looking at the schematics I can't see how shorting out the diode would fix anything, so maybe the schematics are not 100% correct. So I have no idea if it will work from 3.3V, it may even damage the board.
In general it's not a good idea to connect a voltage to an output.
Well shorting that diode did fix it. It now works from a 3.3V input and is still OK when plugged in to USB - without the 3.3V applied at the same time of course.
Maybe thats what their note means - its OK as long as you don't apply an external 5 or 3.3V at the same time as USB ?
I wonder though if a micro sold in this state should be classified as faulty - a lot of people would be expecting to power from battery rather than the USB input.
Thanks for the very helpful hint.
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You are absolutely right. The whole story is posted on this forum :
https://www.letscontrolit.com/forum/viewtopic.php?p=67814#p67814
Actually they put this note when I asked them if their modules are really v1.1 (which fixes the design issue). Apparently not !
I also use external 3.3V and half of my chips were not working. I replaced the diode with a zero-ohm 0805 resistor and they are all back to normal. I now wonder if the newer CH9102 chip (https://www.aliexpress.com/item/1005005933528007.html) does not expose this design issue.
I also bought some modules from here : D1 Mini Pro Lolin ESP8266 Mini Board kompatible Wemos IPEX Arduino Wifi – MAKERSHOP.DE and they have this 0R resistor instead of the diode !
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