you may use the RTS (ready to send ) signal with software
only to generate relative slow PWM

Somewhat faster if use timer/interrupt driven programming.

I can't go into details without spec's.

<nbucska@pcperipherals.com>

Easy, just send a 0x00 to 0xFF out the serial port.  It will give you some were from +/- 5V to +/- 15V, most likely +/- 9V.  It will be slighly off becuase of the start bit - set it up for no parity and only one stop, but it will be a good approximation.  The RTS idea is also pretty good, but liekly to be too slow to drive anything but the simplest loads.  

It also would not be a big deal to simply design a little RS-232 powered dongel with a little "pic" controller that could generate the signal.  You may have to have some eletronics anyway depending on what you are trying to drive.  Are you trying to drive a FET?

Steve Owens
Finish Line Product Development Services
www.FinishLinePDS.com

a 2 chip solution could be had by using a serial D/A converter driving a PWM device. Check Maxim site for possibilities. I'm sure you can get a 12bit version for good resolution.
http://www.maxim-ic.com

Another option is to use the parallel port, which allows you more flexibility, such as using it to read signals as well:

http://www.lvr.com/parport.htm

TTFN

TTFN

Simplest would be to use the PC's loudspeaker output
and internal timer. Send E-mail address for sample program

<nbucska@pcperipherals.com>