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By QuickFix
kaygisizugur wrote:i have a esp 12 e dev kit v0.9 version

What's that? :?
It looks like (actually it's a wild guess) you're talking about a NodeMCU, if not: take a picture of it and post it here (or post a link to the website you bought it). :idea:

If it's a NodeMCU (or similar): those have a UART-USB chip on-board, so you can't use TX and RX without (physically) removing that chip first.
User avatar
By rudy
#84254 The USB to serial chip on the board is connected to the RX and TX lines but there are 470 Ohm resistors between the ESP8266 and the Serial chip. So the RX and TX lines can be use with minor conflict.

The ESP8266 RX pin will look like it has a 470 Ohm pull up resistor connected to the pin. (470 Ohms driven high by the USB-serial chip)

Configuring the ESP8266 RX and TX lines as basic I/O can be found with a search. This has been answered before. And you didn't say what software framework you are using.

The 470 Ohm resistor connected to the rx pin of the USB-serial chip, connected to the ESP8266 will no effect in most cases.
Last edited by rudy on Sun Oct 20, 2019 6:35 pm, edited 1 time in total.