MPR121 Capacitive Touch Sensor Module — 12-Key, I²C, 3.3V/5V, Arduino

MPR121 Capacitive Touch Sensor Module — 12-Key, I²C, Arduino

The MPR121 capacitive touch sensor module detects touch on up to 12 independent electrode inputs using Freescale's MPR121 proximity capacitive touch controller — reporting touch/release events via I²C with an interrupt (IRQ) output for efficient MCU polling. No mechanical switches required — any conductive surface (copper pad, wire, foil, fruit) connected to an electrode input becomes a touch sensor. Widely used for touch keyboards, touch buttons, and human-machine interface (HMI) projects with Arduino and Raspberry Pi.

Module Specifications

• IC: MPR121 (NXP/Freescale)
• Touch Channels: 12 independent capacitive inputs (ELE0–ELE11)
• Interface: I²C (address selectable: 0x5A–0x5D via ADDR pin)
• Supply Voltage: 3.3V (on-board regulator for 5V input)
• Interrupt: IRQ pin (active LOW on touch/release event)
• Sensitivity: Adjustable via touch/release threshold registers
• Auto-calibration: Built-in baseline tracking

Arduino Wiring

• VCC → 3.3V | GND → GND | SDA → A4 | SCL → A5 | IRQ → D2
• Use Adafruit MPR121 library from Arduino Library Manager
• Connect electrodes (wires, copper pads, or conductive objects) to ELE0–ELE11

Typical Applications

• 12-key capacitive touch keyboard
• Touch-sensitive control panel
• Musical instrument touch controller (Theremin-style)
• Fruit piano (banana, orange as touch electrodes)
• Proximity sensor (detect hand approach without contact)

MPR121 capacitive touch module — 12-key, I²C, IRQ, auto-calibration for Arduino touch keyboard, HMI, and capacitive sensing projects.

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