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 the jumper first. Jumpers also connect SDA, SCL and the interrupt pin to 10K pull-up resistors. If you don't require the pull-up resistors you can open the jumpers by cutting the trace connecting them.There is no regulation on the board, so the voltage supplied should be between 2.5 to 3.6VDC. The VREG pin 2.5 and 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).

Overview:

• Proximity Capacitive Touch Sensor with 12 independent sensors
• The MPR121 also features eight LED driving pins
• I2C Interface
• Power supply: 2.5v - 3.6v

Features:

• I2C Compatible
• LED driver functionality with 8 shared LEDs

Specifications:

• Operating voltage: 2.5v - 3.6v
• 29μA supply current at 16ms sample period
• 3μA shutdown current
• 12 electrodes
• Operating temperature range: -40°C to +85°C 
• Weight: 5 g

Implementations:

• General Purpose Capacitive Detection
• Switch Replacements
• Touch Buttons
• Touch Keypad
• Touch Slide bar
• Touch Wheel
• Touchpad
• Touch Panel
• Near Proximity Detection

Application:

• PC Peripherals
• MP3 Players
• Remote Controls
• Mobile Phones
• Lighting Controls

Compatible Product:

• Arduino Uno

Pinouts:

• Vcc - 3.3 V
• Gnd - Gnd
• SCL - Serial Clock
• SDA - Serial Data

Package Includes:

• 1 x MPR121 V12 Proximity Capacitive Touch Sensor Module I2C Interface