Design with Adafruit MPR121 in Cirkit DesignerThe Adafruit MPR121 is a capacitive touch sensor module that features the MPR121 touch controller IC. It is designed to detect electrical changes on its 12 input pins that occur when a touch or proximity event is detected. This module is commonly used in creating touch interfaces, adding touch buttons to electronic projects, and in applications requiring user input without mechanical buttons.
This circuit integrates an Adafruit MPR121 capacitive touch sensor with an Adafruit Feather 32u4 Bluefruit microcontroller. The MPR121 is powered by the Feather and communicates via I2C (SCL and SDA) to detect touch inputs, which can be processed or transmitted wirelessly by the Feather.
Open Project in Cirkit Designer
This circuit integrates an Adafruit MPR121 capacitive touch sensor with an Adafruit Feather 32u4 Bluefruit microcontroller. The MPR121 is powered by the 3.3V supply from the Feather and communicates with the microcontroller via I2C, with SCL connected to pin 3 and SDA connected to pin 2 of the Feather. This setup allows the Feather to detect touch inputs from the MPR121 for further processing or wireless communication.
Open Project in Cirkit Designer
This circuit is a multi-sensor data acquisition system with wireless communication capabilities. It utilizes an Arduino UNO to interface with an MPU-6050 gyroscope, an Adafruit ADXL345 accelerometer, an Adafruit MPR121 capacitive touch sensor, and a SparkFun Electret Microphone for audio input. The system can transmit sensor data via an HC-05 Bluetooth module and an ESP8266 WiFi module, and it includes a bi-directional logic level converter for voltage level matching between devices. The circuit is powered by a 9V battery connected to the Arduino's Vin pin.
Open Project in Cirkit Designer
This circuit is an interactive touch-based MIDI controller and audio player. It uses an Arduino UNO R4 WiFi to interface with an MPR121 capacitive touch sensor for input, a MAX7219 8-digit 7-segment display for visual feedback, and a DFPlayer MINI for audio output through a loudspeaker. The system detects touch inputs, plays corresponding sounds, and sends MIDI notes.
Open Project in Cirkit Designer| Pin Number | Name | Description |
|---|---|---|
| 1 | VIN | Supply voltage (2.5V to 3.6V) |
| 2 | 3Vo | 3.3V output from the onboard regulator |
| 3 | GND | Ground connection |
| 4 | SDA | I2C data line |
| 5 | SCL | I2C clock line |
| 6 | IRQ | Interrupt output (active low) |
| 7-18 | 0-11 | Capacitive touch input pins |
#include <Wire.h>
#include <Adafruit_MPR121.h>
// You can have up to 4 on one i2c bus (connecting ADDR to 3V,
// setting the jumpers to different combinations of connecting them to ground)
Adafruit_MPR121 cap = Adafruit_MPR121();
void setup() {
Serial.begin(9600);
while (!Serial) { // Needed to start serial on some platforms
delay(10);
}
if (!cap.begin(0x5A)) {
Serial.println("MPR121 not found, check wiring?");
while (1);
}
Serial.println("MPR121 found!");
}
void loop() {
// Get the currently touched pads
currtouched = cap.touched();
for (uint8_t i=0; i<12; i++) {
// it if *is* touched and *wasnt* touched before, alert!
if ((currtouched & _BV(i)) && !(lasttouched & _BV(i)) ) {
Serial.print(i); Serial.println(" touched");
}
// if it *was* touched and now *isnt*, alert!
if (!(currtouched & _BV(i)) && (lasttouched & _BV(i)) ) {
Serial.print(i); Serial.println(" released");
}
}
// reset our state
lasttouched = currtouched;
// comment out this line for detailed data from the sensor!
delay(100);
}
Q: Can I use the MPR121 with a 5V microcontroller? A: Yes, but ensure that the MPR121 module is powered with a voltage within its operating range (2.5V to 3.6V). Use level shifters if necessary for the I2C lines.
Q: How can I change the sensitivity of the touch inputs? A: Sensitivity can be adjusted by writing to the MPR121's internal registers. Refer to the MPR121 datasheet for detailed register settings.
Q: How many MPR121 modules can I connect to a single I2C bus? A: You can connect up to 4 MPR121 modules to a single I2C bus by setting different I2C addresses using the address jumpers on the back of the module.