Hello friends, I hope you all are doing great. In today's tutorial, we are gonna have a look at detailed Introduction to MPR121 . MPR121 is a touch sensor controller, its working is like the capacitor's working principle. This module has twelve electrodes points, it communicates via I2C protocol. When any objects come closer to an electrode point, we can observe the presence of an object by variation in capacitance of an electrode. It's working voltage should be between 2.5 to 3.6 VDC. Libraries Touch and Keypad Simulation Libraries Input modules: Joystick · Rotary Encoder · Membrane Keypad · TTP229 Keypad · TTP223 Touch · IR Remote · Fingerprint R307 Helping Tools Serial Monitor Advance : a serial terminal window for the UART of your board Serial Monitor Expert : the serial monitor with e ...