Blink the LEDs on Beagle Bone Black

led.cpp

#include <fstream>
#include <sstream>
#include <stdexcept>
#include "led.h"

using namespace pile;
using namespace std;

LED::LED(int id)
{
    if (id < 0 || id > 4)
        throw invalid_argument("id must be from 0 to 3");
    this->id = id;
    stringstream ss;
    ss << "/sys/class/leds/beaglebone:green:usr" << id << "/brightness";
    this->path = ss.str();
}

void LED::setBrightness(int parcent)
{
    if (parcent < 0 || parcent > 100)
        throw invalid_argument("parcent must be from 0 to 100");
    this->brightness = parcent;
    int duty = 255*parcent/100;
    ofstream os(this->path);
    os << duty;
    os.close();
}

led.h

#pragma once

#include <string>

namespace pile
{
    class LED
    {
    public:
        LED(int id);
        void setBrightness(int parcent);
    private:
        int id;
        int brightness;
        std::string path;
    };
}

main.cpp

#include <iostream>
#include <unistd.h>
#include <memory>
#include "led.h"

using namespace pile;

int main()
{
    std::shared_ptr<LED> leds[4];
    for (int i = 0; i < 4; i++)
        leds[i] = std::shared_ptr<LED>(new LED(i));

    while (true) {
        for (int i = 0; i < 4; i++) {
            std::cout << i << std::endl;
            leds[i]->setBrightness(100);
            sleep(1);
        }
        for (int i = 0; i < 4; i++) {
            std::cout << i << std::endl;
            leds[i]->setBrightness(0);
            sleep(1);
        }    
    }
    
    return 0;
}