MPR121 Capacitive Touch Sensor Module 12-Channel I2C 3.3V

The MPR121 capacitive touch sensor module is a compact I2C touch controller board built around the NXP/Freescale MPR121, designed to replace mechanical buttons with reliable, wear-free capacitive sensing. The controller manages up to 12 independent capacitance sensing electrodes and adds a 13th simulated channel for near-proximity detection using the multiplexed sensing inputs. Eight of the twelve electrode inputs are multifunctional and can be configured as LED drivers or GPIO, giving designers flexibility in user-interface layouts. The module operates from a 1.71V to 3.6V supply, draws only 29µA at a 16ms sampling interval, and falls to 3µA in stop mode, making it suitable for battery-powered and low-energy embedded systems. It provides I2C communication with an interrupt output, and the I2C address can be set to 0x5A, 0x5B, 0x5C, or 0x5D through the ADD pin, allowing multiple controllers on the same bus. The board has no onboard voltage regulator, so the supply must stay within the module’s rated range, and the VREG pin is tied to ground through a 0.1µF capacitor. Automatic configuration and auto-calibration are performed independently for each electrode, with separate touch and release thresholds and debounce control. The MPR121 operates across -40°C to +85°C and is commonly used in touch keypads, control panels, smart devices, and proximity-sensing interfaces.