MPR121 Capacitive Touch Breakout – 12 Input I2C
The MPR121 Capacitive Touch Breakout uses an i2c interface chip and can control up to twelve individual touch pads. The MPR121 also features eight LED driving pins. When these are not configured as electrodes, they can be used to drive LEDs. There is a jumper under four directors, and all of these sets are off by default.
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 can’t operate the MPR121 in low-supply voltage mode (1.71-2.75VDC).
MPR121 Capacitive Touch Breakout Quick Spec:
- Chipset: Freescale MPR121QR2
- Supply Range: 1.71 V to 3.6 V
- Supply current at 16 ms sampling interval period: 29 μA
- Stop mode current: 3 μA
- Inputs: 12
- Interface: I2C with Interrupt output
- I2C Address Range: 0x5A – 0x5D
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 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.