This MPR121 is a capacitive touch sensor controller driven by an I2C interface. The chip can control up to twelve individual electrodes, as well as a simulated thirteenth electrode The MPR121 also features eight LED driving pins, when these pins are not configured as electrodes, they may be used to drive LEDs.?There are four jumpers on the bottom of the board, all of which are set (closed) by default. An address jumper ties the ADD pin to the 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 do not require the pull-up resistors you can open the jumpers by cutting the trace connecting them.