// blinkgpio.cpp
// Author: Jim Merkle  
// Date: 1/25/2017
// Toggle a GPIO pin

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define GPIO_PIN    4

 void msleep(int milliseconds)
 {
     usleep(milliseconds * 1000);
 }

 int main(int argc, char * argv[])
 {
     printf("LED is now Blinking on GPIO %d\n",GPIO_PIN);
     char command[100];
     char command_on[100];
     char command_off[100];
     sprintf(command,"echo %d > /sys/class/gpio/export",GPIO_PIN);
     system(command);
     msleep(500);  // allow time for the system to create directory tree
     sprintf(command,"echo \"out\" > /sys/class/gpio/gpio%d/direction",GPIO_PIN);
     system(command);
     sprintf(command_on,"echo 1 > /sys/class/gpio/gpio%d/value",GPIO_PIN);
     sprintf(command_off,"echo 0 > /sys/class/gpio/gpio%d/value",GPIO_PIN);

      for(int i=0;i<10;i++) {
         system(command_on);
         msleep(200);
         system(command_off);
         msleep(200);
     }
     sprintf(command,"echo %d > /sys/class/gpio/unexport",GPIO_PIN);
     system(command);
     return 0;
 }