MPR121 Hookup Guide

This Tutorial is Retired!

This tutorial covers concepts or technologies that are no longer current. It's still here for you to read and enjoy, but may not be as useful as our newest tutorials.

Contributors: Toni_K
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Capacitive Touch Sensor Breakout Board

The SparkFun Capacitive Touch Sensor Breakout Board is the most versatile option of the three MPR121 products. You can wire it up to any kind of electrode you want, and, as it is a simple breakout board, does not have a particular microcontroller footprint it favors.

SparkFun Capacitive Touch Sensor Breakout - MPR121

5 Retired

The breakout board has 4 pins that need to be connected to your microcontroller at a minimum to get communication going: the power lines and the I2C lines. However, for our example, we are going to be also connecting the IRQ pin to more easily detect a change on one of the electrodes.


MPR121 Breakout → Arduino Uno

  • 3.3V → 3.3V
  • SCL → A5
  • SDA → A4
  • GND → GND
  • IRQ → D2

You will also want to connect the Electrode/LED pins to your electrode material you selected previously. You will want to make sure you have a good, solid connection between your material and your board, so make sure you thoroughly solder your connections.

Check out the Fritzing diagram below for how your connections should look. The yellow squares represent whatever material you decide to use for your electrodes.

Breakout Board Hookup