int zozSerialOpen(unsigned int port, unsigned int baud)
/* opens the serial port, tests for the presence of the stepper and then *
 * returns a handle to the port                                          */
{
  HANDLE hCommDev;
  DCB dcb; // device control block
  COMMTIMEOUTS commTimeOuts;

  char szPort[8];

  char readbuf[16];

  if ((port < 0) || (port > 9))
  {
    printf("Error opening port: port number %d out of range 0..9\n", port);
    return(-1);
  }

  strcpy (szPort, "COM");
  szPort[3] = port+'0'; // to char... works for 0 - 9
  szPort[4] = '\0';

  // open the serial port...
  hCommDev = CreateFile(szPort, GENERIC_READ | GENERIC_WRITE,
                        0,                    // exclusive access
                        NULL,                 // no security attrs
                        OPEN_EXISTING,
                        FILE_ATTRIBUTE_NORMAL,
                        NULL);

  if (hCommDev == (HANDLE)-1)
  {
    printf("Error opening port: couldn't open port %s\n", szPort);
    hCommDev = 0;
    return(-1);
  }
  // get any early notifications
  SetCommMask(hCommDev, EV_RXCHAR);

  // set buffer sizes
  SetupComm(hCommDev, 256, 256);

  // Set the parameters on the comms
  if (!GetCommState(hCommDev, &dcb))
  {
    printf("Error opening port: couldn't get current DCB settings\n");
    return(-1);
  }
  // set baud rate...
  switch (baud)
  {
    case 1200:
      dcb.BaudRate = CBR_1200;
      break;
    case 2400:
      dcb.BaudRate = CBR_2400;
      break;
    case 4800:
      dcb.BaudRate = CBR_4800;
      break;
    case 9600:
    default:
      dcb.BaudRate = CBR_9600;
      break;
    case 19200:
      dcb.BaudRate = CBR_19200;
      break;
    case 38400:
      dcb.BaudRate = CBR_38400;
      break;
    case 57600:
      dcb.BaudRate = CBR_57600;
      break;
    case 115200:
      dcb.BaudRate = CBR_115200;
      break;
  }

  dcb.fBinary = TRUE;
  dcb.fOutxCtsFlow = FALSE;
  dcb.fOutxDsrFlow = FALSE;
  dcb.fDsrSensitivity = FALSE;
  dcb.fOutX = FALSE;
  dcb.fInX = FALSE;
  dcb.fNull = FALSE;
  dcb.fAbortOnError = FALSE;
  dcb.fDtrControl = DTR_CONTROL_DISABLE;
  dcb.fRtsControl =  RTS_CONTROL_DISABLE;
  dcb.fAbortOnError = 0; // don't abort on error

  dcb.ByteSize = 8; // 5, 6, 7, or 8
  dcb.Parity = NOPARITY;
  dcb.StopBits = ONESTOPBIT;

// setting size recommended by Microsoft's serial I/O web page
  dcb.DCBlength = sizeof(dcb);
  if (!SetCommState(hCommDev, &dcb))
  {
    printf("Error opening port: couldn't set comm state - possible invalid DCB structure\n");
  }

  commTimeOuts.ReadIntervalTimeout = 0xFFFFFFFF;
//  timeout = bytesToBeWritten * multiplier + Constant(milliseconds)
  commTimeOuts.ReadTotalTimeoutMultiplier = 0;
  commTimeOuts.ReadTotalTimeoutConstant = 1000; // milliseconds
  commTimeOuts.WriteTotalTimeoutMultiplier = 0;
  commTimeOuts.WriteTotalTimeoutConstant = 1000;
  SetCommTimeouts(hCommDev, &commTimeOuts);
  // setup overlapped

  PurgeComm(hCommDev, PURGE_TXABORT | PURGE_RXABORT | PURGE_TXCLEAR | PURGE_RXCLEAR);
  zozWriteChar(hCommDev, '?'); // check for stepper activity
  Sleep(50); // pause for reset

  if (!zozCanRead(hCommDev))
  {
    printf("Error opening port: no response from reset command\n");
    return(-1);
  }

  zozRead(hCommDev, readbuf, sizeof(readbuf));

  printf("Port status: %s\n", readbuf);

  return((int)hCommDev);
}

void zozSerialClose(HANDLE hSerialDev)
/* closes serial port - not really necessary but friendly */
{
  CloseHandle(hSerialDev);
  return;
}

int zozCanRead(HANDLE hSerialDev)
/* checks for non-empty receive buffer */
{
  COMSTAT cs;
  DWORD dwErrors;

  // seems to be the only way to get COMSTAT
  if (!ClearCommError (hSerialDev, &dwErrors, &cs))
  {
    printf("Error: ClearCommError failed in zozCanRead()\n");
    return FALSE;
  }
  return cs.cbInQue != 0;
}

int zozRead(HANDLE hSerialDev, char *psz, int maxlen)
/* reads data from receive buffer, up to maxlen chars */
{
  DWORD readLen;

  ReadFile(hSerialDev, psz, maxlen, &readLen, 0);

  // need to null-terminate it for ascii
  psz[readLen] = '\0';

  return(readLen);
}

void zozWrite(HANDLE hSerialDev, char *psz, int len)
/* writes a string to a serial device */
{
  DWORD writtenLen;

  if (len == 0)
  {
    len = strlen(psz);
  }

  if (!WriteFile(hSerialDev, psz, len, &writtenLen, 0))
  {
    if (GetLastError() != ERROR_IO_PENDING)
    // WriteFile failed, but isn't delayed.  Report error.
    {
      printf("Error: write failed\n");
    }
  }
}

void zozWriteChar(HANDLE hSerialDev, char c)
/* writes a single character to a serial device */
{
  char cmd[2];

  cmd[0] = c;
  cmd[1] = '\0';

  zozWrite(hSerialDev, cmd, 1);
}