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By jgalak
#198202
I have a project I'm working on that I'd like to program using the 3V3 version of the FTDI basic breakout. However, the overall power needs of the project will likely exceed the current output of the FTDI Basic's regulator (50mA). The project will have its own regulator, providing 3V3 to the circuit and to the ATmega. Can I simply leave the 3V3 pin (pin 3) disconnected? Is there any problem with doing that?

(Yes, I know I can get a Beefy 3 that'll provide plenty of current, but that'll make the circuitry more complicated, as I don't want to back-feed the project's regulator.)

I suppose I can switch the FTDI to 5V mode and feed the output to the project regulator input, but that seems annoying.

Thanks!
By Valen
#198273
TX, RX and GND should suffice to make the communication working. To be safe use a resistor of a few hundred ohms in series with TX and RX. Any voltage difference between TX and the opposing device RX (and vice versa) will have the current limited by the resistor.