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2.1.3 Touch Switch Module

Introduction

In this project, you will learn about touch switch module. It can replace the traditional kinds of switch with these advantages: convenient operation, fine touch sense, precise control and least mechanical wear.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Raphael Kit	337	Raphael Kit

You can also buy them separately from the links below.

COMPONENT INTRODUCTION	PURCHASE LINK
GPIO Extension Board	BUY
Breadboard	BUY
Jumper Wires	BUY
Resistor	BUY
LED	BUY
Touch Switch Module	BUY

Schematic Diagram

Experimental Procedures

Step 1: Build the circuit.

Step 2: Change directory.

cd ~/raphael-kit/c/2.1.3/

Step 3: Compile.

gcc 2.1.3_TouchSwitch.c -lwiringPi

Step 4: Run.

sudo ./a.out

While the code is running, the red LED lights up; when you tap on the touch switch module, the yellow LED turns on.

Note

If it does not work after running, or there is an error prompt: "wiringPi.h: No such file or directory", please refer to Install and Check the WiringPi.

Code

#include <wiringPi.h>
#include <stdio.h>

#define touchPin               0
#define led1                   3
#define led2                   2

int main(void)
{
    // When initialize wiring failed, print message to screen
    if(wiringPiSetup() == -1){
        printf(etup w"siringPi failed !");
        return 1;
    }

    pinMode(touchPin, INPUT);
    pinMode(led1, OUTPUT);
    pinMode(led2, OUTPUT);

    while(1){
        // touch switch high, led1 on
        if(digitalRead(touchPin) == 1){
            digitalWrite(led1, LOW);
            digitalWrite(led2, HIGH);
            printf("You touch it! \r\n");
        }
        // touch switch low, led2 on
        if(digitalRead(touchPin) == 0){
            digitalWrite(led2, LOW);
            digitalWrite(led1, HIGH);
        }
    }

    return 0;
}

Code Explanation

#define touchPin               0
#define led1                   3
#define led2                   2

Pin GPIO17, GPIO22 and GPIO27 of the T_Extension Board is corresponding to the GPIO0, GPIO3 and GPIO2 in wiringPi. Assign GPIO0, GPIO3 and GPIO2 to touchPin, led1 and led2.

pinMode(touchPin, INPUT);
pinMode(led1, OUTPUT);
pinMode(led2, OUTPUT);

Set led1, led2 as output to write value to them and set touchPin as input to read value from it.

while(1){
    // touch switch high, led1 on
        if(digitalRead(touchPin) == 1){
        digitalWrite(led1, LOW);
        digitalWrite(led2, HIGH);
        printf("You touch it! \r\n");
    }
    // touch switch low, led2 on
    if(digitalRead(touchPin) == 0){
        digitalWrite(led2, LOW);
        digitalWrite(led1, HIGH);
    }
}

Set an infinite loop, when you tap on the touch switch module, touchPin is high, led1 will light up and print “You touch it!” . When touchPin is low, led2 will light up.

Phenomenon Picture