ESP32 Modules with CH340 USB Chips Running at 5V instead of 3.3v on Tx/Rx?

These ESP32 modules have a CH340 USB chip configured to run at 5v instead of 3.3v so I'm fixing these. Some modules also have weird wifi signal strength issues but I can't seem to improve that on all of them.
Discussion on ESP32 with CH340 issues community.home-assistant.io/t...
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[@mikejones-vd3fg]

Nice find, clever fix, interesting mystery...

[@diyertime]

I usually buy the versions that use an external antenna so that I have some freedom to get better signal coverage.

[@silverback3633]

Very good explanation. USB IC provides the level shifting when it is connected to a 5V USB port. Why CH340 is connected to 5V? Doesn't cost anything, in fact they could have saved those 2 resistors. About the RSSI, would like to see the difference between the original modules from ESSPRESSIF and the clones.

[@DontEatFibre]

So my RX is 5V as well, while the TX is 3.3v This is when powering from USB. Powering from 3V3, RX is 2.6V and TX is 3.3V.

[@DontEatFibre]

If someone can tell if the RX dropping that low is to be expected while not transmitting, please let me know.

[@gadgetsideload]

is that while applying 3.3 V to the Vin pin? and is that with a CH 340 chip? I think the module vin pin is intended to take higher than 3.3 V so the onboard regulator can bring it down to 3.3 but I’m not sure if the regulator on these modules just passes through 3.3 in to out without a drop out. having 2.6 on the Rx pin is definitely not normal and it’s around the bottom threshold for detecting logic high which I think is 2.65 V when running at 3.3 V so it definitely needs to be run differently to get that back to 3.3 V.