LPT or GPINT-PT problem

Questions about hardware and software obtained directly from Shoestring Astronomy
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Justice
Posts: 1
Joined: Fri Aug 29, 2008 3:55 pm

LPT or GPINT-PT problem

Post by Justice » Fri Aug 29, 2008 5:26 pm

Hello. I have been having trouble with interfacing a GPINT-PT to a laptop running Win XP Pro. With the first -PT, all the pins were in low (-0.7 V) state regardless of the buttons used in GPINTCheck. After a lot of testing and emails with Doug, and trying on a second computer (a DELL at work, also XP pro), we decided the -PT was bad and he sent me another one (Great Service !!). However, that one showed the same problem.

After re-reading some posts on the Forum, I came across a post talking about LPT modes set in BIOS, and using EPP mode. On my laptop I only have "output-only", "Bi-directional", and ECP. I thought ECP was back-compat. with EPP so I tried that. It had been on "bi-directional".
In ECP, the outputs were all 0V until I clicked a button on GPINTCheck. At that piont, the affected (propper) pin would DROP TO -0.7 Volts ! (progress ??)

I tried it on my OLD home system (XP Home) and the native ECP+EPP 1.9 mode and got the same as with the laptop in ECP mode (0V to -0.7V).

Anybody have any ideas? Do I need to run something like the "Add New Printer Wizard" to let the computer know that something is attached to the LPT-1 port?

I am checking these by running a ShoeString cable from the GPINT-PT to a 6-connector wall box so I can get to the leads with some room. I have a second, "reversed" cable, and it shows the same problem, except that pin 5 is now pin 2, as expected.

I appreciate any help, Thanks

Jeff

g__day
Posts: 3
Joined: Mon Sep 12, 2011 1:54 am
Anti-spam question: Astronomy

Re: LPT or GPINT-PT problem

Post by g__day » Mon Sep 12, 2011 8:04 am

I originally had a problem simlar to this - a Printer port (unlike a USB port) is not initialised to a defined state in Windows XP. You can get around this with some slight trickery.

1. Download a freeware Hex editor
2. Use it to create a file called empty.bin
3. Insert just hex 00 (a null) into empty.bin and save it to a prefered location
4. Use notepad to create a batch command file called clear_auto_guider.bat
5. In this file write (without the quotes) "copy /b c:\empty.bin LPT1"
6. Under Control Panel -> Schedule Tasks create a new task that runs clear_autoguider upon boot up

Problem should be solved! What this does is on WIndows start-up send a HEX null (using copy /b for binary - no trnalsation) to the LPT1 parallel port, which then gets remembered so it sets the Port's data lines to zero - no movement!

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