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Merge pull request #2559 from arduino/pedromsousalima/r4/touch-tutorial
[PXCT-1073] Tutorial from library - Uno R4 Capacitor Tutorial
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‎content/hardware/02.hero/boards/uno-r4-wifi/tutorials/touch/assets/HoockupGuideExample.png

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‎content/hardware/02.hero/boards/uno-r4-wifi/tutorials/touch/assets/Touch_Cover_001.gif

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‎content/hardware/02.hero/boards/uno-r4-wifi/tutorials/touch/content.md

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---
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title: UNO R4 Capacitive-Touch Tutorial.
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difficulty: beginner
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description: Learn to use the built-in capacitive sensing capabilities of the Arduino® UNO R4.
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tags: [Arduino, Capacitive Sensing, UNO R4]
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author: Pedro Lima
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hardware:
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- hardware/02.hero/boards/uno-r4-wifi
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- hardware/02.hero/boards/uno-r4-minima
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software:
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- ide-v2
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- web-editor
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---
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Capacitive sensing is a technology that detects changes in capacitance to determine the presence or absence of a conductive object, such as a human finger. This principle is widely used in touch-sensitive devices. The Arduino® UNO R4, both the [WiFi®](https://store.arduino.cc/products/arduino-uno-r4-wifi) and [Minima](https://store.arduino.cc/products/arduino-uno-r4-minima) versions, come equipped with built-in capacitive sensing capabilities, making it easier to integrate touch inputs into your projects.
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![Sensor Example](assets/Touch_Cover_001.gif)
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## Required Hardware
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To use the library, you will need one of the compatible boards:
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- [Arduino® UNO R4 WiFi](https://store.arduino.cc/products/uno-r4-wifi)
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- [Arduino® UNO R4 Minima](https://store.arduino.cc/products/uno-r4-minima)
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You will also need:
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- Wire
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- Something that can affect the electric field to touch (metal objects, materials with moisture, even bananas! Experimentation is key!)
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## How Capacitive Sensing Works
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Imagine the sensor as creating an invisible electric field around itself. When a conductive object (like your finger) approaches, it's like dropping a stone into a calm pond - the field gets disturbed. The sensor detects this disturbance as a change in capacitance, which is essentially how much electrical charge the system can store.
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Here's the process:
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1. The sensor electrode creates an electric field by applying a small voltage
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2. When you approach or touch the sensor, your body becomes part of the capacitive circuit
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3. This increases the capacitance between the sensor electrode and ground
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4. The microcontroller detects this capacitance change (often by measuring timing differences) and determines if it's significant enough to register as a "touch"
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## Using Capacitive Sensing on the UNO R4
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The UNO R4 features a Capacitive Touch Sensing Unit (CTSU) that allows you to use certain pins as capacitive touch inputs. To utilize these capabilities, you can use the [Arduino_CapacitiveTouch library](https://github.com/arduino-libraries/Arduino_CapacitiveTouch).
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### Compatible Pins
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For both the UNO R4 WiFi® and Minima boards, the compatible pins for capacitive touch are listed in the [Arduino_CapacitiveTouch library documentation](https://github.com/arduino-libraries/Arduino_CapacitiveTouch?tab=readme-ov-file#compatible-pins).
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**Arduino® UNO-R4 Minima:**
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| Arduino Pin | Touch Sensor Channel (TS#) | Channel Control Index (CHAC idx) | Channel Control Bit Mask (CHAC val) |
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|--------------|----------------------------|----------------------------------|-------------------------------------|
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| D0 | 9 | 1 | (1 << 1) |
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| D1 | 8 | 1 | (1 << 0) |
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| D2 | 34 | 4 | (1 << 2) |
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| D3 | 13 | 1 | (1 << 5) |
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| D8 | 11 | 1 | (1 << 3) |
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| D9 | 2 | 0 | (1 << 2) |
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| D11 | 10 | 1 | (1 << 2) |
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| D13 | 12 | 1 | (1 << 4) |
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| A1 (D15) | 21 | 2 | (1 << 5) |
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| A2 (D16) | 22 | 2 | (1 << 6) |
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| LOVE_BUTTON | 0 | 0 | (1 << 0) |
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**Arduino® UNO-R4 WiFi®:**
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| Arduino Pin | Touch Sensor Channel (TS#) | Channel Control Index (CHAC idx) | Channel Control Bit Mask (CHAC val) |
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|--------------|----------------------------|----------------------------------|-------------------------------------|
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| D0 | 9 | 1 | (1 << 1) |
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| D1 | 8 | 1 | (1 << 0) |
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| D2 | 13 | 1 | (1 << 5) |
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| D3 | 34 | 4 | (1 << 2) |
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| D6 | 12 | 1 | (1 << 4) |
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| D8 | 11 | 1 | (1 << 3) |
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| D9 | 2 | 0 | (1 << 2) |
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| D11 | 7 | 0 | (1 << 7) |
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| D12 | 6 | 0 | (1 << 6) |
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| A1 (D15) | 21 | 2 | (1 << 5) |
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| A2 (D16) | 22 | 2 | (1 << 6) |
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| LOVE_BUTTON | 27 | 3 | (1 << 3) |
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### Library Functions
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The **Arduino_CapacitiveTouch** library provides several functions to work with capacitive touch inputs:
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- **`CapacitiveTouch(uint8_t pin)`** Constructs a capacitive touch sensor for the given pin.
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- **`bool begin()`** Initializes the sensor and configures the pin and hardware.
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- **`int read()`** Reads the raw sensor value and returns it.
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- **`bool isTouched()`** Checks if the sensor is touched based on the threshold.
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- **`void setThreshold(int threshold)`** Sets the detection threshold for touch sensitivity.
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- **`int getThreshold()`** Retrieves the current detection threshold.
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For more detailed usage and examples, refer to the [CapacitiveSensor library documentation](https://github.com/arduino-libraries/Arduino_CapacitiveTouch/blob/main/docs/api.md).
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## Detecting Touch Example
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### Circuit
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Here's a simple example to get you started with capacitive sensing on the UNO R4. For this example, we are connecting a single piece of any conductive material to the pin `D0` on the Board.
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![How to connect](assets/HoockupGuideExample.png)
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### Code
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**Note:** To install the `Arduino_CapacitiveTouch` library, open the Arduino IDE Library Manager, search for "Arduino_CapacitiveTouch" within the Manage Libraries option, and click Install.
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```arduino
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#include "Arduino_CapacitiveTouch.h"
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CapacitiveTouch touchButton = CapacitiveTouch(D0);
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void setup() {
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Serial.begin(9600);
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if(touchButton.begin()){
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Serial.println("Capacitive touch sensor initialized.");
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} else {
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Serial.println("Failed to initialize capacitive touch sensor. Please use a supported pin.");
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while(true);
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}
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touchButton.setThreshold(2000);
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}
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void loop() {
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int sensorValue = touchButton.read();
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Serial.print("Raw value: ");
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Serial.println(sensorValue);
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if (touchButton.isTouched()) {
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Serial.println("Button touched!");
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}
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delay(100);
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}
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```
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![Sensor Example](assets/Touch_Cover_001.gif)
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## Creative Project Ideas
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Now that you have learned the basics, here are some fun and interesting project ideas:
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- **Touch-Controlled Night Light -** Create a lamp that turns on/off with a touch
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- **Capacitive Touch Piano -** Use multiple pins to create touch-sensitive keys
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- **Smart Home Controller -** Touch different areas to control various devices
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- **Interactive Art Installation -** Create touch-responsive visual or audio effects
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## Conclusion
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Capacitive sensing on the Arduino UNO R4 lets you add intuitive touch controls with minimal hardware. Simply pair the board with the `Arduino_CapacitiveTouch` library. Tune the detection threshold for your environment (such as humidity and nearby electronics), and you can quickly scale from a single-touch button to richer, multi-point interfaces.

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