Ich mache das mit JAVA!
Ungefähr so:
Code:
import javax.comm.*;
...

serialPort=open("COM1");
serialPort.setSerialPortParams(2400, SerialPort.DATABITS_8,SerialPort.STOPBITS_1, SerialPort.PARITY_NONE);
outputStream = serialPort.getOutputStream();

...
outputStream.write(char);
...
mit
Code:
SerialPort open(String name) throws PortInUseException {
	CommPortIdentifier portId;

	Enumeration portList;

	portList = CommPortIdentifier.getPortIdentifiers();

	while (portList.hasMoreElements()) {
		portId = (CommPortIdentifier) portList.nextElement();
		if (portId.getPortType() == CommPortIdentifier.PORT_SERIAL) {
			if (portId.getName().equals(name)) {
				return (SerialPort) portId.open(name, 2000);
			}
		}
	}	
	return null;
}

Tut's