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MPR121 Breakout I2C Capacitive Touch Sensor Controller Module
This is a breakout board for Freescales MPR121QR2. The 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 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 dont 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 and 3.6VDC. The VREG pin is connected through a 0.1uF capacitor to ground£¬ which means£¬ unless you modify the board£¬ you cant operate the MPR121 in low-supply voltage mode (DC 1.71~2.75V).