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Com / LPT parallel...

Discussion in 'Hardware' started by ajseguin, Dec 5, 2011.

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  1. ajseguin

    ajseguin Thread Starter

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    Ok, i have a Professional Sony Laser Disc Player and it has a RS-232C female, 25-pin. So i had a DB-25 male to DB-25 male cable so, for fun i pluged it to a pc with win xp, and to the controller port. I downloaded the free controller software from this site: http://www.laserdiscarchive.co.uk/laserdisc_archive/sony/sony_laserdisc_archive.htm. so everything is plugged, it even displays on the laserdisc player there is and external controller plugged to it. So the problem is: it's plugged in a LPT port and the dos software requires COM... So i got 2 different adapters and turns out one was for modem and so is the other one, but i'm just assuming. so i'm wondering is there really and RS-232 adapter from DB-25 to DB9? or i can do something to change the LPT port to COM. because the laser disc does display it's connected to a controller and it does not when used with the numerous adapters. Oh and i also tried batch files with some comands they guive on the site, and trying LPT1 instead of COM1 and it doesn't work either.

    Thanks AJSEGUIN
     
  2. cwwozniak

    cwwozniak Trusted Advisor Spam Fighter

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    Hi AJSEGUIN, and welcome to TSG.

    LPT and COM ports use two totally different signalling methods. If the computer is a desktop with an open expansion card slot, you might be able to add an RS-232 card that will be recognized by the software.

    The player may be showing that it is connected because it is detecting a voltage on a certain input pin, but is not actually communicating with anything.
     
  3. ajseguin

    ajseguin Thread Starter

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    thanks, so rs-232 is not the same thing as a serial port db-9 connector that many motherboards have? And can i get an rs-232 card with a db-25 connection?
     
  4. Triple6

    Triple6 Moderator

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    The 9 pin male port on the PC is always a serial port(RS-232) which is referenced as COM1/2/etc. A parallel port on the PC is always female 25 pin port referenced as LPT1/2/etc. On extremely old computers you may find a 25 male serial port but in most cases they are 9 pin and you'd use a 25 pin to 9 pin cable.

    Very few devices require the need for a 25 pin cable, but the device may still have a 25 pin port but work with a 9 pin cable.

    The Sony is therefore plugged into a Serial/COM port already and not a parallel/LPT port.

    Make sure you have the correct COM port selected in the software as is set in the computer, check Device Manager to see what the serial port is set as, ie. COM1, COM2, COM3, COM4, etc.

    There's also two common types of serial cables, straight through and a cross-over cable called a null-modem cable, the one site said it uses a null-modem cable and another one said it uses a custom serial cable but I'm sure thats true if it states RS-232c which would be standard serial. One site also mentioned that some of the software runs under pure DOS only and not in Windows command prompt window.
     
  5. ajseguin

    ajseguin Thread Starter

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    ok, ok... well my model is the LDP 2000 and it specifies rs-232 so from what you both said, i'll just search for a db-9 to db25 cable that is straight through and not modem...

    Thanks
     
  6. ajseguin

    ajseguin Thread Starter

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    oh sorry, well do you have a trick to differentiate the modem and standard cable? other then the packaging... because i know a used pc part store who sells miscellaneous old cables for cheap and most of the stuff is unpacked...
     
  7. ajseguin

    ajseguin Thread Starter

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    [​IMG]

    i checked one of my adapters with a multimeters, and it has the same pin out as in this picture
     
  8. Triple6

    Triple6 Moderator

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    There may be something printed on the cable itself, otherwise from the outside they look the same.

    Edit, yes using a multi-meter will work to identify the cable.

    Pinout: http://en.wikipedia.org/wiki/Null_modem
     
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