internal static extern bool SetCommState(IntPtr hFile, [In] ref Dcb lpDCB);
public static IntPtr OpenPort(int portNum, RS232Config config)
{
// Validate inputs
if (portNum < 0 || portNum > 255)
{
throw new ArgumentException("Invalid port number (valid range is [0, 255]).", nameof(portNum));
}
if (!config.IsValid(out var msg))
{
throw new ArgumentException(msg, nameof(config));
}
// Open the port
var fileName = "\\\\.\\COM" + portNum;
var hPort = RS232PInvoke.CreateFileA(
fileName, // File name for com port
FileAccess.ReadWrite, // Read/Write access for (rx/tx)
FileShare.None, // no share
IntPtr.Zero, // no security
FileMode.Open, // open existing
FileAttributes.Normal, // normal file
IntPtr.Zero); // no template file
if (hPort.ToInt32() == -1)
{
Marshal.ThrowExceptionForHR(Marshal.GetHRForLastWin32Error());
}
// Configure the port
var dcb = new Dcb
{
BaudRate = (uint)config.BaudRate,
ByteSize = (byte)config.DataBits,
Parity = config.Parity,
StopBits = config.StopBits,
};
if (!RS232PInvoke.SetCommState(hPort, ref dcb))
{
RS232PInvoke.CloseHandle(hPort);
throw new Exception("Could not configure COM port settings.");
}
// Configure the port time-outs
var timeouts = new COMMTIMEOUTS
{
// Read operations return immediately
ReadIntervalTimeout = 0xFFFF_FFFF, // MAXDWORD
ReadTotalTimeoutMultiplier = 0,
ReadTotalTimeoutConstant = 0,
// Timeouts not used for write operations
WriteTotalTimeoutMultiplier = 0,
WriteTotalTimeoutConstant = 0,
};
if (!RS232PInvoke.SetCommTimeouts(hPort, ref timeouts))
{
RS232PInvoke.CloseHandle(hPort);
throw new Exception("Could not configure COM port timeouts.");
}
// Return port handle for caller
return(hPort);
}