Here is the poor man's way to light an LED with the serial port:
You may have to play with the resistor value dependent on the type of LED you are using. The serial port normally puts out 12v on the DTR line when activated. With a 510 ohm resistor, this would give about 23 mA to the LED. Make sure the LED ratings can handle 23 mA. If not, you may have to make the resistor value larger. If the LED can handle more, you make it brighter by lowering the resistor value.
To assert DTR, look up a Labview example on serial communications. You can set a property node for DTR I believe. True/False to turn it on or off.
Message Edited by tbob on 03-08-2007 12:21 PM
Thanks tbob for giving him the pin out and circuit.
The code to turn on you circuit is attached.
Also wanted to let him know that the a USB DIO module (NI USB-6501) is only $100.