ESP32 Forum

Hello,
In the Datasheet for ESP32-S2 I see that for UART1 pins are: RX GPIO18 and TX GPIO17.
https://www.espressif.com/sites/default ... eet_en.pdf

but here I see for ESP32-S2 UART1 using different pins . RX is GPIO21 and TX GPIO17
https://docs.espressif.com/projects/esp ... -s2-series

What is the correct pin of RX ?

There's no discrepancy between those documents. The ESP32-S2 has a GPIO matrix that allows signals like the UART receive and transmit lines to be routed to any GPIO, even if they have 'default' GPIOs according to the datasheet. I imagine the AT firmware (as described in the second document you mention) has some reason to re-route the UART to different pins than the startup defaults (as documented in the first document).

Hello,
I am using AT firmware and I followed the second documentation. UART1 communication on that particular pins doesn't work. That's why I started searching for reason.

Then you can confirm that the pinpoint in second document for AT firmware is correct.