//Program controls peripherals through GPIOs
//Source & info: www.HomoFaciens.de
//http://www.HomoFaciens.de/technics-computer-internet-of-things_en_navion.htm
//v 0.1
//compile with: gcc GPIO-status.c -lwiringPi -o GPIO-status
//Program checks the status of a GPIO (which will be switched to input mode before).
//Return code is (1) if the switch is open (HIGH signal)
//Return code is (2) if the switch is closed (LOW signal)

#include <wiringPi.h>
#include <softPwm.h>
#include <stdio.h>


//Define the GPIO numbers the peripherals are connected to
//Header pin      GPIO number
//       P1-3               8
//       P1-5               9
//       P1-7               7-
//       P1-8              15
//       P1-10             16
//       P1-11              0-
//       P1-12              1-
//       P1-13              2-
//       P1-15              3-
//       P1-16              4-
//       P1-18              5-
//       P1-19             12
//       P1-21             13
//       P1-22              6-
//       P1-23             14
//       P1-24             10
//       P1-26             11


static void usage(){
  printf("Program reads status of GPIOs.\n");
  printf("Examples of usage:\n");
  printf("Test GPIO number 5:                            ./GPIO-status 5\n");
}


int main (int argc, char **argv){
  int i;
  int gpioNumber = 0;

  //Quit program if less than 1 argument were passed
  //argv[1] is the first argument, argv[1] the second, ...
  if(argc < 2){
    usage();
    return(0);
  }
  
  if (wiringPiSetup () == -1)
    return(-1) ;

  gpioNumber = atoi(argv[1]);
  
  if(gpioNumber < 0 || gpioNumber > 17){
    printf("Invalid GPIO number %d! Must be between 0 and 17!\n", gpioNumber);;
    return(0);
  }
  
  pinMode (gpioNumber, INPUT);
  pullUpDnControl (gpioNumber, PUD_OFF);//Disable pullup / pulldown resistor

  if(digitalRead(gpioNumber) == 1){
    printf("Switch at GPIO %d is OPEN\n", gpioNumber);
    return(1);
  }
  else{
    printf("Switch at GPIO %d is CLOSED\n", gpioNumber);
    return(2);
  }

  return 0 ;
}