MPR121 Touch sensor module can be easily interfaced with I2C interface and can be used to control up to twelve individual electrodes, as well as a simulated thirteenth electrode. This module is based on MPR121 which is a proximity capacitive touch controller. The MPR121 also features eight LED driving pins. When these pins are not configured as electrodes, they may be used to drive LEDs.

There is no regulation on the board, so the voltage supplied should be between 2.5 and 3.6VDC. The VREG pin is connected through a 0.1uF capacitor to ground, which means, unless you modify the board, you can’t operate the MPR121 in low-supply voltage mode (1.71-2.75VDC).

There a four jumpers on the bottom of the board, all of which are set (closed) by default. An address jumper ties the ADD pin to ground, meaning the default I2C address of the chip will be 0x5A. If you need to change the address of the chip (by shorting ADD to a different pin), make sure you open.