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#ifndef GPIO_CLASS_H #define GPIO_CLASS_H #include <string> using namespace std; /* GPIO Class * Purpose: Each object instantiated from this class will control a GPIO pin * The GPIO pin number must be passed to the overloaded class constructor */ class GPIOClass { public:    GPIOClass();  // tạo 1 GPIO object để điều khiển GPIO4 (mặc định)    GPIOClass(string x); // tạo 1 GPIO object để điều khiển GPIOx, x được truyền vào thông qua hàm khởi tạo    int export_gpio(); // exports GPIO    int unexport_gpio(); // unexport GPIO    int setdir_gpio(string dir); // Set GPIO Direction    int setval_gpio(string val); // Set GPIO Value (putput pins)    int getval_gpio(string& val); // Get GPIO Value (input/ output pins)    string get_gpionum(); // trả về chỉ số GPIO tương ứng với 1 object private:    string gpionum; // GPIO number : lưu trữ chỉ số của gpio  }; #endif

#include <fstream> #include <string> #include <iostream> #include <sstream> #include "GPIOClass.h" using namespace std; GPIOClass::GPIOClass() {    this->gpionum = "4"; //GPIO4 is giá trị mặc định cho hàm khởi tạo không có tham số truyền vào } GPIOClass::GPIOClass(string gnum) {    this->gpionum = gnum;  // hàm khởi tạo có thông số truyền vào cho gpionum là gnum } int GPIOClass::export_gpio() {    string export_str = "/sys/class/gpio/export";    ofstream exportgpio(export_str.c_str()); // Thực hiện mở file "export" . Convert C++ string to C string. Required for all Linux pathnames    if (exportgpio < 0){        cout << " OPERATION FAILED: Unable to export GPIO"<< this->gpionum <<" ."<< endl;        return -1;    }    exportgpio << this->gpionum ; //write GPIO number to export    exportgpio.close(); //close export file    return 0; } int GPIOClass::unexport_gpio() {    string unexport_str = "/sys/class/gpio/unexport";    ofstream unexportgpio(unexport_str.c_str()); //Open unexport file    if (unexportgpio < 0){        cout << " OPERATION FAILED: Unable to unexport GPIO"<< this->gpionum <<" ."<< endl;        return -1;    }    unexportgpio << this->gpionum ; //write GPIO number to unexport    unexportgpio.close(); //close unexport file    return 0; } int GPIOClass::setdir_gpio(string dir) {    string setdir_str ="/sys/class/gpio/gpio" + this->gpionum + "/direction";    ofstream setdirgpio(setdir_str.c_str()); // open direction file for gpio        if (setdirgpio < 0){            cout << " OPERATION FAILED: Unable to set direction of GPIO"<< this->gpionum <<" ."<< endl;            return -1;        }        setdirgpio << dir; //write giá trị direction đến direction file (là 'in' hoặc 'out')        setdirgpio.close(); // close direction file        return 0; } int GPIOClass::setval_gpio(string val) {    string setval_str = "/sys/class/gpio/gpio" + this->gpionum + "/value";    ofstream setvalgpio(setval_str.c_str()); // open value file for gpio        if (setvalgpio < 0){            cout << " OPERATION FAILED: Unable to set the value of GPIO"<< this->gpionum <<" ."<< endl;            return -1;        }        setvalgpio << val ;//write value to value file        setvalgpio.close();// close value file        return 0; } int GPIOClass::getval_gpio(string& val){    string getval_str = "/sys/class/gpio/gpio" + this->gpionum + "/value";    ifstream getvalgpio(getval_str.c_str());// open value file for gpio    if (getvalgpio < 0){        cout << " OPERATION FAILED: Unable to get value of GPIO"<< this->gpionum <<" ."<< endl;        return -1;            }    getvalgpio >> val ;  //read gpio value    if(val != "0")        val = "1";    else        val = "0";    getvalgpio.close(); //close the value file    return 0; } string GPIOClass::get_gpionum(){ return this->gpionum; }

#include <iostream> #include <unistd.h> #include <errno.h> #include <stdio.h> #include <stdlib.h> #include "GPIOClass.h"   using namespace std;   int main (void) {       string inputstate;     GPIOClass* gpio4 = new GPIOClass("4"); //create new GPIO object to be attached to  GPIO4     GPIOClass* gpio17 = new GPIOClass("17"); //create new GPIO object to be attached to  GPIO17       gpio4->export_gpio(); //export GPIO4     gpio17->export_gpio(); //export GPIO17       cout << " GPIO pins exported" << endl;       gpio17->setdir_gpio("in"); //GPIO4 set to output     gpio4->setdir_gpio("out"); // GPIO17 set to input       cout << " Set GPIO pin directions" << endl;       while(1)     {         usleep(500000);  // wait for 0.5 seconds         gpio17->getval_gpio(inputstate); //read state of GPIO17 input pin         cout << "Current input pin state is " << inputstate  <<endl;         if(inputstate == "0") // if input pin is at state "0" i.e. button pressed         {             cout << "input pin state is "Pressed ".n Will check input pin state again in 20ms "<<endl;                 usleep(20000);                     cout << "Checking again ....." << endl;                     gpio17->getval_gpio(inputstate); // checking again to ensure that state "0" is due to button press and not noise             if(inputstate == "0")             {                 cout << "input pin state is definitely "Pressed". Turning LED ON" <<endl;                 gpio4->setval_gpio("1"); // turn LED ON                   cout << " Waiting until pin is unpressed....." << endl;                 while (inputstate == "0"){                  gpio17->getval_gpio(inputstate);                 };                 cout << "pin is unpressed" << endl;               }             else                 cout << "input pin state is definitely "UnPressed". That was just noise." <<endl;           }         gpio4->setval_gpio("0");       }     cout << "Exiting....." << endl;     return 0; }