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Re: [midatlanticretro] [Semi-OT] Dot Matrix Printer Help

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  • Kyle Owen
    ... I can certainly check on that. It s definitely the only connector on the printer. I imagine it does have a UART, but I ll have to tear it apart again.
    Message 1 of 7 , Feb 25 8:52 AM
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      On Mon, Feb 25, 2013 at 6:44 AM, David Gesswein <djg@...> wrote:
       

      On Mon, Feb 25, 2013 at 12:59:33AM -0600, Kyle Owen wrote:
      > The DB-25 connector on the back
      > is actually part of a removable module.
      >
      I would pull the module and trace the wiring to the connector. Do one or
      both of pins 2 & 3 go to some RS-232 interface chip? Is 7 ground? Does
      the module have a UART on it? Is this the only connector on the printer?

      From which pin goes to the receiver you can tell if its wired DTE or DCE.
      You might need a null modem.

      I can certainly check on that. It's definitely the only connector on the printer. I imagine it does have a UART, but I'll have to tear it apart again. 

      RS-232 is still very confusing to me. I've got a Northstar Horizon that can use one type of cable to interface with a terminal or my USB-serial adapter, but my Data I/O EPROM programmer requires a null modem cable, as does my Tandy 200, if I recall. I've tried the null modem cable with the printer and was getting garbage characters, which tells me I'm on the right track, I suppose.

      Kyle 
    • Kyle Owen
      ... Thanks Wesley, and thanks to your coworker as well. Here s a better picture of the actual printer I have: http://i.imgur.com/KLROR89.jpg And yes, I expect
      Message 2 of 7 , Feb 25 8:58 AM
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        On Mon, Feb 25, 2013 at 7:43 AM, Wesley Furr <wesley@...> wrote:
         

        Kyle,
         
        I passed your message on to someone I work with now, and worked with two jobs back too.  "Back in the day" of the other job, they used to use Sperry/Unisys equipment...so I passed along your note in case he knew something about your printer.  I personally worked with some of the leftover big MT band printers...but nothing smaller that had that name on it.  Here's his response:
         
         
         
        Well – up until I displayed the picture I thought I was familiar with the printer.   I have dealt with MT printers in the past – I don’t think they had the Unisys name on them though.  The picture and the MT printer I have in mind do not match.
         
        The MT’s that I played with had a menu that would allow the print of the current and all possible settings – it printed quite a long list of configurable parameters.
         
        If the printer has the Unisys name on it – it may have a butchered serial interface.  Depending on what the printer was connected to in its Unisys life, it may not be a typical serial connection.  Long ago we purchased an Epson printer to replace a Unisys (maybe even Sperry) printer and there was a slight change to the serial settings to get it to talk to a Unisys terminal.   But this slight change was made with a dip switch.
         
        In the very last paragraph there is a statement…” but I honestly didn't expect the printers to hold me back!”
         
        In my experience – printers ALWAYS hold you back.   I thought at one point that printers and modems would cause the end of life as we know it.
         
        Sorry – a lot of words -  not much help…..
         
        djp
         
        Hope this is of some help...
         
        Thanks,
         
        Wesley

        Thanks Wesley, and thanks to your coworker as well. 

        Here's a better picture of the actual printer I have: http://i.imgur.com/KLROR89.jpg

        And yes, I expect *modern* printers to hold me back, but c'mon...a dot matrix from 1988? Give me a break! :)

        Kyle
      • Kelly D. Leavitt
        ... I think a lot of the old Sperry/Unisys stuff was 7-bit even parity. That might be what the printer is expecting for serial data. Try setting the comm port
        Message 3 of 7 , Feb 25 9:16 AM
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          > RS-232 is still very confusing to me. I've got a Northstar Horizon that can
          > use one type of cable to interface with a terminal or my USB-serial
          > adapter, but my Data I/O EPROM programmer requires a null modem cable, as
          > does my Tandy 200, if I recall. I've tried the null modem cable with the
          > printer and was getting garbage characters, which tells me I'm on the right
          > track, I suppose.

          I think a lot of the old Sperry/Unisys stuff was 7-bit even parity. That might be what the printer is expecting for serial data.

          Try setting the comm port to that if you can and send it data again using the null modem cable.

          Serial is "simple" in some respects in that it is mostly understandable, and slow enough to troubleshoot a bit with an inexpensive scope. rx on one end goes to tx on the other. There are two basic types of devices DTE and DCE. DTE devices are meant to connect to DCE devices, the null modem converts one end from one flavor to another. See http://en.wikipedia.org/wiki/Data_terminal_equipment for some background. Handshaking gets a bit bothersome sometimes, but us usually understandable.

          Don't expect too much data back from the printer other than handshaking. Serial printers were typically bit consumers not bit producers.
        • Wesley Furr
          Well...if you go back far enough before serial and centronics were very standardized... :-) Someone else comment about 7E and presumably 1 for serial
          Message 4 of 7 , Feb 25 7:24 PM
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            Well...if you go back far enough before serial and centronics were very standardized...  :-)  Someone else comment about 7E and presumably 1 for serial settings...that would seem to go along with the comment about a serial setting change.  Gotta love all the serial options!  Like I've heard it said before...the great thing about standards is there are so many to choose from!
             
            Good luck!
             
            Wesley
             
             

            From: midatlanticretro@yahoogroups.com [mailto:midatlanticretro@yahoogroups.com] On Behalf Of Kyle Owen
             

            Thanks Wesley, and thanks to your coworker as well. 

            Here's a better picture of the actual printer I have: http://i.imgur.com/KLROR89.jpg

            And yes, I expect *modern* printers to hold me back, but c'mon...a dot matrix from 1988? Give me a break! :)

            Kyle
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