Here's a quick 'n dirty program to send arbitrary values to the parallel/printer/lpt port on a pc. It was written on and for an openbsd box that will be used to control the radio transmitter for Ithaca Radio. The parallel port will connect to a couple of relays to mute the audio, and select between alternate input signals.

It has some normal defaults, so use should be pretty straightforward. In a nutshell:

xctl [-h|-?] [-p port] [value]

-h or -? prints a short usage message.

Examples:

xctl -h

prints the help screen.

xctl

sends a 0 to port 378 (hex).

xctl 3

sends a 3 to port 378 (hex).

xctl -p 278 13

sends a 13 to port 278 (hex).

Oh, by the way... Either a feature or bug, but it will only allow the default ports of 378, 278, and 3bc to be specified.

• Here's the source code: xctl.c
• ...a precompiled binary that was built and tested (a little) on a x586 running 3.2: xctl
• ...a precompiled binary that was built and tested on a x686 running 4.3: xctl43
• The circuit's pretty simple; I've built variations on this theme for years: relay.ps

enjoy!
...dave