Com port service/app for digital IO

**momanz** · 12-03-2004, 01:32 AM

I was wondering if anyone has considered writing a application/service that would use all of the available com port control lines as digital IO lines? As far as I can tell each com port has the following available...

DTR pin 4 output control (drives a relay to control an antenna motor)
RTS pin 7 output control (drives a relay to switch an amp on or off)
CTS pin 8 input (signals when to shutdown/hibernate)
DCD pin 1 input (use for...)
DSR pin 6 input (handbrake switch to enable/disable video in players)
RI pin 9 input (use for ...)

There are a couple of applications that use single pins on the com port for various control functions (AmpCtrl uses pin 7, Shutdown and XP's UPS service use pin 8, I think Frodo uses pin 6 for video lockout). I've tried using Comfoolery and Com Port Redirector to create several virtual com ports and then assign each application (shutdown, frodo, ampctrl) each to its own virtual com port, but only ampctrl worked properly. Using the virtual com ports I wasn't getting any video with frodo, XP went into hibernation once I started the UPS service, and Shutdown crashed. I'm pretty sure I have my virtual ports working because I can run multiple GPS programs without a problem and CPR does report that the applications are connecting to the virtual ports.

I'm thinking if we had a program or service dedicated to properly forwarding these control signals to virtual com ports app writers and users could have some extra digital I/O to play with.

Anyone think this could work? Has it already been done and am I about to get flamed?

-momanz

**Dominik** · 12-03-2004, 01:37 AM

I think it would be better to use the Parallel port - who the hell has a printer in their car anyway?

there would be alot more inputs/outputs available that way... (My Com port is for my GPS!!)

Does anyone know if this would work?

**dragonBTV** · 12-03-2004, 02:43 AM

I have a print port control one, but can NOT work with 2000/xp

**Dominik** · 12-03-2004, 05:30 AM

Why is that?

**rando** · 12-03-2004, 11:38 AM

..because you can't get low level control of the parallel port pins in NT/2000/XP without installing a PortIO driver or developing one of your own. Either way, software has to be specially tailored to whatever driver you use.

**weekendowel** · 12-03-2004, 11:40 AM

Originally Posted by rando

..because you can't get low level control of the parallel port pins in NT/2000/XP without installing a PortIO driver or developing one of your own.

But you can control it without a PortIO driver, I can do it.

**zorro** · 12-03-2004, 02:33 PM

Look here: http://www.logix4u.net

**TechToy** · 12-03-2004, 02:51 PM

I used a parallel port relay module for 5 minutes unitll i rebooted and relays were triggered in XP's startup sequence.. so i combined that parallel boards relays/driver with the weeder tech serial DIO module http://weedtech.com/wtdio-m.html and was working great, the weeder app is also decent switch designs etc... but has an annoying startup screen that has to be "ok'd" i'd tie some screen caps to the msg but i just got a NEW explorer and have to re-equip.. btw.. also used the analog module to read voltages off the main and aux batteries... works great...
just my .02