Hi,
I am using the round display with the esp3c3 and
I would like to know id there are pin(s) available to interface with external device??
(I know that I can use sda, sck for the IIC protocol). But, I am taking about unused pin of the esp32c3 (normally, all the pins are connected to the round display), thank
You can use these;
KE Button & GPIO
On the new version of the Round Display, we have designed a KE switch to selectively release
certain GPIOs for selective use by the user.
The KE switch is designed in the middle of the microSD card slot and the row of pins that
connect to the XIAO.
The circuit design for this switch is shown below.
This means that when the switch is closed (toggled to the ON side) then the Round Display's
battery voltage reading function and display backlight function become available.
When the switch is disconnected (toggled to the digital side), then pins A0 and D6 on the XIAO
are the available states.
HTH
GL 
PJ