This is a matrix keyboard running along with an LCD display and an Arduino Uno, the most basic that exists today. The purpose of this setup is to create a program that receives a password typed on the matrix keyboard, compares it with the correct password, and displays a confirmation message on the display.
It is important to remember that both the matrix keyboard and this display work with ESP8266 and ESP32.
As you can see, we power the circuit with the Arduino with a USB, since we are not using an external source. Eight wires connected in a very simple way to the Arduinos ports make the connection of our keyboard. This keyboard has no power and is passive, which greatly facilitates the connections.
The display is connected with an Arduino via the UART, the serial port, which also powers the device.
In a demonstration, we show in the video our circuit checking if the password typed on the keyboard is correct or not.
In the PDF used in the video and available here, we have the complete pinout of the chip being used.”