Overview
There is only 1-ch UART port on the original Raspberry Pi, once it is used for terminal debugging, no more other serial device is allowed. What a poor situation. Now you have 2-ch extra UART, plus 8 programmable GPIOs, just bring this Serial Expansion HAT.

Features
Standard Raspberry Pi 40PIN GPIO extension header, compatible with Raspberry Pi Zero/Zero W/Zero WH/2B/3B/3B+/4B and later versions
Onboard SC16IS752, expands 2-ch UART and 8 programmable GPIO through I2C, no extra pin required
It is stackable up to 16 this modules by setting the address jumper, that means up to 32-ch UART
Onboard multi LEDs for indicating the UART working status
Reserved I2C control pins, allows to work with other control boards
Comes with development resources and manual (examples in C and python)

Specifications
Operating voltage: 3.3V
Expansion chip: SC16IS752
Control interface: I2C
Dimension: 65mm x 30mm
Mounting hole size: 3.0mm

Package Contains :
Serial Expansion HAT x1
RPi screws pack (2pcs) x1
PH2.0 6PIN wire x2

For more details you may need to know, pls firstly send me message via Amazon, I will then send attached link including User Guide for you, thank you for patience.:)