The Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121) is a multichannel proximity capacitive touch sensor. It's a 3-in-1 module with the following features: Capacitance Sensing, Touch Sensing, and Proximity Sensing.

Capacitance Sensing: This module uses a constant DC current capacitance sensing scheme. It can measure capacitances ranging from 10 pF to over 2000 pF with a resolution up to 0.01 pF.

Touch Sensing: Once the electrode capacitance data is acquired, the electrode touch/release status is determined comparing it to the capacitance baseline value.

Proximity Sensing: One new feature of the MPR121 is the near proximity sensing system. This means that all of the system’s electrodes can be summed together to create a single large electrode.

Based on Freescale MPR121, this sensor have 12 completely independent electrodes with build-in autoconfiguration. Thanks to I2C interface, you can detect all the 12 electrodes signals with only one Grove port, and the I2C address is hardware configurable, from 0X5B to 0X5D. This also makes it possible for multiple Grove - 12 Key Capacitive I2C Touch Sensor V2 (MPR121) to be used together for channel expansions in a single system, you can build a touch system which contains max. 36 electrodes.