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By RobRob
SparkFun Serial Basic Breakout - CH340G

Is is ok to have an external power source connected while using the Serial Basic? I'm using a breadboarded Arduino (atmega328) with 5V supplied by LM7805 regulator with smoothing caps and protection diode and resettable fuse.

Can I just not connect VCC and GND on the Serial Basic?

If it is ok, are there any other things I need to consider?

Thanks, Robby R.
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By chipace
If your ch340g is configured for 5V operation (by default it is 3.3v, you would need to cut a trace and solder 2 pads) then there is no issue with 5.0v external power being present. Just don't use that modified ch340g to connect to a 3.3V part later (you will damage the 3.3v part).