RVR Serial Port Power Proteced?

I have aSparkfun ESP32 Thing connected for serial communications on the serial (not USB) port. The ESP32 is powered by the power pin on the serial port. On the ESP32 the power pin used is directly connected to the USB +5 power line. (It is actually labeled VUSB.)

If I connect the ESP32 to my PC with a USB cable for programming that will put the USB 5v on the RVR’s 5v pin. Is that okay or will the back feed cause problems? I’m guessing it will but checking to be sure.

While that might be okay, the 5V buck regulator on RVR has over-voltage protection that’s not well documented. It’s possible you could get into some weird behavior between the two switching regulators, so I’d recommend using some kind of diode OR-ing.