How to override various errors

Posted on 2006-04-29
Last Modified: 2010-04-12

I have a laser engraver which is basically an hpgl plotter.  The plotter came with its own windows based software for designing want you want to engrave AND for driving the engraver.  So far, this is working (but their software is limited to pixel based graphics)  It is also supposed to work as a stand alone engraver.  According to the manual, I should be able to install an hpgl compatible printer driver so that I can "plot" straight from windows apps (As in - I want to plot from a CAD program)

I have tried many plotter, vinyl cutter and engraver drivers, but I always get the same error - "Can not print. Printer is out of paper".  Uh, since there is no paper tray in this device, there are no paper sensors.

The engraver itself has few switches. Just a power switch and a laser on button. There are no little swiches on the output card.

Connects to computer via 36pin centronics/25pin cable to parallel port 1 (lpt1)(And have tried LPT2).  Computer is P3 600Mh 512 Mb Win 98.  I need Windows to run various software, but would consider 2k or XP if that helps.

Here is what I have tried so far:
installed a quality, configurable HPGL driver
LPT1 and LPT2
setting LPT1 to output only - std bidirectional - EPP - ECP
printing from CAD
printing test from driver interface
printing from DOS prompt
printing from DOS

For what it's worth,  I periodically connect an inkjet to do test prints and to verify that the ports are really working and both ports print fine.

I am willing to build a "grappler", if I need to override pin12 or any of the status pins, but would prefer to do that with settings on my computer...Besides, i can see how I could force pin 12 low but not sure how to set pin 15 high and curious about Ack and Init ...

The people in China from whom I purchased the engraver say they couldn't get it to work (though it does say that it should in the manual) and that was the end of the support.

Hoping to find a real expert who can help me debug the handshake signals so I can cut some vectors.

 I am thinking this is dificult - 500 points - Thanks
Question by:lazerCut-SEM
    LVL 37

    Accepted Solution

    Have you tried connecting pin 12 to ground (pins 18-25 on a DB-25 connector)? Use a 1000 ohm resistor to do this, as shorting the pin to ground may possibly damage the port.

    Leaving pin 15 unconnected sets it high to indicate "no error". You can also try connecting pin 11 (printer busy, error) to ground

    Author Comment

    Hello hdhondt ,

    Thanks for the reply.  I will be wiring this up shortly to try it out.

    I want to be sure that I do this correctly, so let me please ask...

    Lets suppose for a moment that I were to take a parallel cable and cut it in half.  One end would go to the computer and one end goes to the device.  Obviously, most of the connectionss would be straight-forward, like this:

    Modified Parallel Conection

      Computer                                 Device

      strobe        1 --------------------- 1     strobe
      Data 0        2 --------------------- 2     Data 0
      Data 1        3 --------------------- 3     Data 1
      Data 2        4 --------------------- 4     Data 2
      Data 3        5 --------------------- 5     Data 3
      Data 4        6 --------------------- 6     Data 4
      Data 5        7 --------------------- 7     Data 5
      Data 6        8 --------------------- 8     Data 6
      Data 7        9 --------------------- 9     Data 7
      -Ack         10 --------------------- 10    -Ack

      +SelectIn  13 --------------------- 13    +SelectIn
      -AutoFd    14 --------------------- 14    -AutoFd
      -Error       15 --No connection -- 15    -Error
      -Init          16 --------------------- 16    -Init
      -Select     17 --------------------- 17    -Select
      Ground18-25 --------------------- 18-25 Ground

    Then, pins 11 and 12 on the computer side get grounded to any ground 18-25 on the computer side

      +Busy        11 ---1k ohm resistor--- 18-25 Ground
      +PaperEnd 12 ---1k ohm resistor--- 18-25 Ground

    So then, Pins 11,12 and 15 remain disconnected on the device side.

    Does this sound correct?



    LVL 37

    Expert Comment

    It does not matter at which end you ground it, as the ground connections go all the way through, as do the data lines

    Author Comment

    I wired up a connection with pins 11 and 12 tied to ground with 1k resistors and with pin 15 disconnected.

    It improved the situation, in that when I attempt to plot, I no longer get any error messages.  But I am still not successfully plotting.

    If I have THEIR software installed and configure their software to LPT1 then I can use their software to plot (even with the new cable).
    Also, with their software, I can output a .PLT file which gives me an hp-gl file configured (I would think) to their device.

    But, when I try to plot that .plt file outside of their software, it does not work.

    I have tried switching their software to a different port, uninstalling their software, making sure that all other printer drivers are not set to that port and still, no dice.

    from DOS, I have tried:

    copy test.plt lpt1
    copy /b test.plt lpt1

    which will start to move the head, but then the head just returns home. This tells me that the port is working and trying to talk to the plotter, but it isn't quite working.  


    I will continue to try to get the computer talking to the plotter, but any help would be appreciated.

    Any way to determine what the plotter needs to be driven properly?

    LVL 37

    Expert Comment

    I'm sorry, without knowing a lot more about the software and hardware, there is not much I can say. You say that you can plot from within the software, but sending the .PLT file to the plotter does not achieve anything. You think the .PLT file is HPGL - but you're not certain. Also, how sure are you that the plotter is an HPGL device? When you open the .PLT file in a text editor, does it look like HPGL?

    Unfortunately HPGL is not the most device-independent plotter language. For example, the plotter may understand all the commands, but the HPGL code may tell it to plot outside its plotting area. That would explain why the head moves to the home position without plotting anything. HPGL depends on the plotting area and on the location of the coordinate origin on your device.

    It is possible that, unless the manufacturer can help, you may have to live with the fact that you can only plot from within their software.

    Author Comment

    Well, you may be correct that I have to live with it.

    Just for clarity:
    I am certain that the .plt file IS hpgl
    I am not certain if that .plt is configured for their engraver.

    Thanks for your help - the cable solution got me through to the next step.


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