Hướng dẫn cách lập trình điều khiển GPIO trên Raspberry pi bằng C++

#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;
}