led-cpp/MLed.cpp

/*OOP in C++ example for LEDs */
#include<iostream>
#include<fstream>
#include<string>
#include<sstream>
using namespace std;

#define LED_PATH "/sys/class/leds/beaglebone:green:usr"

class LED{
private:
  string path;
  int number;
  virtual void writeLED(string filename, string value);
  virtual void removeTrigger();
public:
  LED(int number);
  virtual void turnOn();
  virtual void turnOff();
  virtual void flash(string delayms);
  virtual void outputState();
  virtual ~LED();
};

LED::LED(int number){
  this->number = number;
  ostringstream s;
  s << LED_PATH << number; // LED number to the Path
  path = string(s.str()); // convert to string
}

void LED::writeLED(string filename, string value){
  ofstream fs;
  fs.open((path + filename).c_str());
  fs << value;
  fs.close();
}

void LED::removeTrigger(){
  writeLED("/trigger", "none");
}

void LED::turnOn(){
  cout << "Turning LED" << number << "on" << endl;
  removeTrigger();
  writeLED("/brightness", "1");
}

void LED::turnOff(){
  cout << "Turning LED" << number << "off" << endl;
  removeTrigger();
  writeLED("/brightness", "0");
}

void LED::flash(string delayms ="50"){
  cout << "Making LED" << number << "flash" << endl;
  writeLED("/trigger", "timer");
  writeLED("/delay_on", delayms);
  writeLED("/delay_off", delayms);
}

void LED::outputState(){
  ifstream fs;
  fs.open((path + "/trigger").c_str());
  string line;
  while(getline(fs,line)) cout << line <<endl;
  fs.close();
}

LED::~LED(){
  cout << "!!Destroying the LED with path: " << path << endl;
}

int main(int argc, char* argv[]){
  if(argc!=2){
    cout << "The usage is main <command>" << endl;
    cout << "<command> is on, off flash or status" << endl;
    cout << "e.g. main on" << endl;
  }
  cout << "Starting program ..." << endl;
  string cmd(argv[1]);
  LED leds[4] = {LED(0), LED(1), LED(2), LED(3)};
  for(int i=0; i<=3; i++){
    if(cmd=="on")
      leds[i].turnOn();
    else if(cmd=="off")
      leds[i].turnOff();
    else if(cmd=="flash")
      leds[i].flash("100");
    else if(cmd=="status")
      leds[i].outputState();
    else
      cout << "invalid command, please type main" << endl;
  }
  cout << "Program done, Thanks." << endl;
  return 0;
}