I'm trying to understand how serial communication for ESP8266 in NodeMCU actually works. I found a quote saying that normal Serial is mapped to ports GPIO 1 (TX) and GPIO 3 (RX). They are even labeled on the board like this, so I believe this is true.

However I'd like to understand the relationship between those pins and serial communication over USB. Does this work the same way as in normal Arduino where you can use either communication over USB or hardware serial on pins 0 & 1?

I did some tests and if I run simple program like:

Serial.println("Hello world");

I can see that in serial monitor on my PC. How does that impact serial communication on GPIO 1 & 3 ?

1 Answer 1


Yes, it is the same as Arduino. The TX and RX pins connect to a CH340G chip to convert the serial into USB. If you use USB serial you can't use the pins for anything else.

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