MPR121 Capacitive Touch Sensor I2C

This is a breakout board for Freescale's MPR121QR2. The MPR121 is a capacitive touch sensor controller powered by an I2C interface. The chip can drive up to twelve individual electrodes as well as a simulated thirteenth electrode. The MPR121 also has eight LED drive pins. If these pins are not configured as electrodes, they can be used to drive LEDs.

There are four jumpers at the bottom of the board, all of which are set (closed) by default. An address jumper connects the ADD pin to ground, which means the chip's default I2C address is 0x5A. If you need to change the address of the chip (by shorting ADD to another pin), you must open the jumper first. Jumpers also connect SDA, SCL and the interrupt pin with 10k pull-up resistors. If you don't need the pull-up resistors, you can open the jumpers by cutting the connecting line.

There is no control on the board, so the voltage supplied must be between 2.5 and 3.6 VDC. The VREG pin is connected to ground via a 0.1uF capacitor, which means that unless you modify the board, you cannot use the MPR121 in low voltage mode (1.71-2.75VDC).