//
// Quick demo - Play with modem signals.
//
// tvb 08-March-2003
//

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

int Port;

//
// Handshake pin functions
//

void DtrOpen ();
void DtrClose ();
void DtrMinusV ();
void DtrPlusV ();
void Wait1PPS ();

void TestDsr ()
{
    int i;
    time_t t;

    printf("Test: read DSR (DE9 pin 6)\n");
    printf(" - rising edge detect on DSR\n");

    DtrOpen();
    for (i = 0; i < 10; i += 1) {
        Wait1PPS();
        time(&t);
        printf("Caught pulse on DSR %s", ctime(&t));
    }
    DtrClose();
}

void TestDtr ()
{
    int i;

    printf("Test: write DTR (DE9 pin 4)\n");
    printf(" - assert DTR (+12 V) for 4 seconds\n");
    printf(" - deassert DTR (-12 V) for 1 second\n");

    DtrOpen();
    for (i = 0; i < 10; i += 1) {
        printf("+");
        DtrPlusV();
        _sleep(4000);

        printf("-");
        DtrMinusV();
        _sleep(1000);
    }
    DtrClose();
}

//
// RS-232 DE9S (9-pin female socket)
// as seen from cable going into PC.
//
//     5   4   3   2   1
//  -----------------------
//  \  O   O   O   O   O  /
//   \                   /
//    \  O   O   O   O  /
//     -----------------
//       9   8   7   6
//
// RS-232 DE9P (9-pin male plug)
// as seen from back of PC
//
//     1   2   3   4   5
//  -----------------------
//  \  .   .   .   .   .  /
//   \                   /
//    \  .   .   .   .  /
//     -----------------
//       6   7   8   9
//
// Signals (PC is DTE)
//
// pin 1 - DCD (PC input)
// pin 2 - Rx  (PC input)
// pin 3 - Tx  (PC output)
// pin 4 - DTR (PC output)
// pin 5 - gnd
// pin 6 - DCE (PC input)
// pin 7 - RTS (PC output)
// pin 8 - CTS (PC input)
// pin 9 - RI
//
// Quiescent Voltages:
//
//  1   2   3   4   5   6   7   8   9
//
//  -   -  -12 -12  0   -  +12  -   -
//

void main (int argc, char *argv[])
{
    if (argc > 1) {
        Port = atoi(argv[1]);

    } else {
        Port = 1;
    }

    // Toggle DTR a few times
    TestDtr();

    // Look for 1 PPS on DSR
    TestDsr();
}


// ------------------------------------------------------------------------ //

//
// Win32 specific code for modem signals.
//

#include <windows.h>

#define ASSERT_SUCCESS(Function) \
    if (!Success) { \
        fprintf(stderr, "File %s Line %d Function %s failed (%.8x)\n", \
               __FILE__, __LINE__, #Function, GetLastError()); \
        exit(1); \
    }

HANDLE hCom;

void DtrOpen()
{
    char CommPath[100];
    DCB Dcb;
    BOOL Success;

    sprintf(CommPath, "\\\\.\\COM%d", Port);
    hCom = CreateFile(CommPath,
                      GENERIC_READ | GENERIC_WRITE,
                      0,
                      NULL,
                      OPEN_EXISTING,
                      0,
                      NULL);

    if (hCom == INVALID_HANDLE_VALUE) {
        fprintf(stderr, "CreateFile failed: %s (%.8x)\n",
                CommPath, GetLastError());
        exit(1);
    }

    memset(&Dcb, 0x0, sizeof(DCB));
    Dcb.DCBlength = sizeof (DCB);
    Success = GetCommState(hCom, &Dcb);
    ASSERT_SUCCESS(GetCommState);

    Dcb.Parity = NOPARITY;
    Dcb.BaudRate = 9600;
    Dcb.ByteSize = 8;
    Dcb.StopBits = ONESTOPBIT;

    Dcb.fDtrControl = DTR_CONTROL_ENABLE;
    Dcb.fRtsControl = RTS_CONTROL_ENABLE;

    Success = SetCommState(hCom, &Dcb);
    ASSERT_SUCCESS(SetCommState);

    printf("Opened: %s\n", CommPath);
    return;
}

void DtrClose ()
{
    CloseHandle(hCom);
    return;
}

//
// Deasserting DTR makes the pin -12 V (nominal)
//

void DtrMinusV ()
{
    BOOL Success;

    Success = EscapeCommFunction(hCom, CLRDTR);
    ASSERT_SUCCESS(EscapeCommFunction);

    return;
}

//
// Asserting DTR makes the pin +12 V (nominal)
//

void DtrPlusV ()
{
    BOOL Success;

    Success = EscapeCommFunction(hCom, SETDTR);
    ASSERT_SUCCESS(EscapeCommFunction);

    return;
}

//
// Wait for rising edge of DSR (DB9 pin6)
//

void Wait1PPS ()
{
    DWORD Modem;
    int New, Old;
    BOOL Success;

    New = 1;
    do {
        Success = GetCommModemStatus(hCom, &Modem);
        ASSERT_SUCCESS(GetCommModemStatus);

        Old = New;
        New = (Modem & MS_DSR_ON) ? 1 : 0;

    } while ( !(Old == 0 && New == 1) );
}