Reading the state of a serial port pin

Another thing, you can wait the signal to change status using "WaitCommEvent", in this case remember to use the "SetCommMask" function before.

WaitCommEvent http://msdn2.microsoft.com/en-us/library/aa363479.aspx
SetCommMask http://msdn2.microsoft.com/en-us/library/aa363435.aspx

Hi,
Thanks for your comment marcodalzotto, I have tried to code it, but not really sure what I am doing. Do you think this looks about right?

#include <windows.h>
#include <iostream>
#include <string>
using namespace std;





int main(int argc, char *argv)
{
             HFILE hCOM = CreateFile(
             "COM1",                       // pointer to name of the file
             GENERIC_READ | GENERIC_WRITE, // access (read-write) mode
             0,                            // share mode
             NULL,                         // pointer to security attributes
             OPEN_EXISTING,                // how to create
             NULL,                         // file attributes
             NULL                          // handle to file with attributes to copy
             );

      while(1)
            {
            //check the status of the pin
            bool pinStatus = GetCommModemStatus(hCOM,MS_CTS_ON);

            if(pinStatus)
                  cout << "Pin is switched on";
            else
                  cout << "Pin is switched off";
            
            }
            
       return 0;      
}


Thanks for your help!
Regs.
John

It's not totally correct, try this way:

int main(int argc, char *argv)
{
  DWORD event, status;

  HANDLE hCOM = CreateFile(
  "COM1",                       // pointer to name of the file
  GENERIC_READ | GENERIC_WRITE, // access (read-write) mode
  0,                            // share mode
  NULL,                         // pointer to security attributes
  OPEN_EXISTING,                // how to create
  NULL,                         // file attributes
  NULL                          // handle to file with attributes to copy
  );

  // sets the event/s that brake the WaitCommEvent
  SetCommMask(hCOM, EV_CTS);

  if (hCOM == INVALID_HANDLE_VALUE)
  {
    cout << "Error opening com port";
    return 1;
  }

  while(1)
  {
    event = status = 0;
            if(WaitCommEvent(hCOM, &event, NULL))
    {
      if(event & EV_CTS) // if the CTS has changed
      {
        //check the status of the pin
        if(GetCommModemStatus(hCOM, &status))
        {
          if(status & MS_CTS_ON) cout << "Pin is switched on";
          else cout << "Pin is switched off";
        }
      }
    }
  }          
 
  return 0;      
}

Cheers,
I will have to go away and learn I think! I tried to compile the code you posted and it gave me the following message:
13 [Warning] passing NULL used for non-pointer converting 6 of `void* CreateFileA(const CHAR*, DWORD, DWORD, _SECURITY_ATTRIBUTES*, DWORD, DWORD, void*)'

Any ideas??
Thanks for all your help!

Is it working ignoring the warning?