Hi~~
I have already implemented the board , and now I am trying to understand the library, but I have some part I can't understand, could you help me to explain it , thank you very much.

This is the part that defines the IO expander pins in the EITKitArduino.h file, but I don't understand which part of the circuit this is.
ESP32_EIT.pdf
Here is the circuit of my board,
Sincerely,
MilesLeeee
Hi~~

I have already implemented the board , and now I am trying to understand the library, but I have some part I can't understand, could you help me to explain it , thank you very much.
This is the part that defines the IO expander pins in the EITKitArduino.h file, but I don't understand which part of the circuit this is.
ESP32_EIT.pdf
Here is the circuit of my board,
Sincerely,
MilesLeeee