How do I control serial power using LabView?

[Kurlie]

I need to use LabView to alter the voltage coming from the serial port. Is it as easy as writing to the serial port? I know that if you write to the serial port that it'll produce a binary number, does this binary number correspond to a voltage.

[Dennis_Knutson]

The output pins of a serial port are either on or off. The output voltage should be about +/- 12V though you're liable to see some variation but you cannot change a logic one from +2V to +5V for example. There's no mechanism in the pc's UART to do such a thing. The binary output corresponds to a character (in the cse of the Tx line) or a control signal (i.e. Request to Send is either on or off).

[Kurlie]

So you are saying that it is impossible because the power from the serial port does not vary?

[Dennis_Knutson]

The logic levels vary between 0 and 1. The voltage associated with a logic level does not vary.

[X]

If you want to create a scalable voltage value coming from the serial port you must have a Dig -> Analog conversion circuit.
If your goal is to vary a voltage from 1 - 10 vdc, then you must create:
1) a an external circuit that will convert/buffer digital serial interfaced binary values to analog values (ni makes these things)
2) labview code that transfers info to serial port. (driver/etc)
hope that helps!
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