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serial rs232 cable help?

Discussion in 'General Electronics Chat' started by BryWY, Apr 6, 2016.

  1. Les Jones

    Les Jones Well-Known Member

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    Connect the positive (Red) test lead to pin 5 and touch the negative (Black) test lead on the pin you are testing.
     
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  2. BryWY

    BryWY Member

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    colors to female end of serial cable going in pc
    1brn
    2red
    3yel
    4brn
    5grn
    6brn
    7blu
    8wht
    9 no reading

    OK from cable coming from pc these are the negative readings:

    brown -22
    yellow-28
    blue-28

    I bought a new standard cable I am willing to cut up to make this work
     
    Last edited: Apr 7, 2016
  3. BryWY

    BryWY Member

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    OK I think I am ready to take the plung Can someone help me through this last bit...hopefully the added readings help anything else ?
     
  4. dave

    Dave New Member

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  5. BryWY

    BryWY Member

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    on plotter pin 3 gives a negative -20
     
  6. Les Jones

    Les Jones Well-Known Member

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    I think your meter is reading high. I do not think the voltages from the PC serial port will be that high. For our purpose at the moment this does not matter. You still have not given any voltage readings from the 9 pin D connector on the plotter so we still don't know which pin on the plotter is transmit and receive. One will be on pin 2 and the other on pin 3 but we need to know which way round they are. You could use straightened out paper clips to make connections to the female connector on the plotter end or you could touch your meter probes on the back of the connectors on the flat cable you have. DO NOT plug the other end of the cable into the PC while doing this test.

    EDIT. I have just seen your post #44. This confirms that a crossover (Null modem.) is required. I suggest that you rewire your flat cable to Ron's null modem diagram in post #2 You may still have to add links between pins 1, 4, & 6 at the PC end so it is the same as your original cable.
    Time to go to bed now in the UK. I have no idea which time zone you are in.

    Les.
     
    Last edited: Apr 7, 2016
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  7. BryWY

    BryWY Member

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    on plotter pin 7 gives a positive of around 20 and 3 is around neg 20
     
  8. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    Voltage levels up to +-025 V are perfectly fine. Wikipedia confirms.

    Wikipedia:
    True. The PC side will be less. Probably more like 12 V.


    that diagram missed CTS and RTS entirely. These are supposed to be the hardware flow control signals.

    Here's a diagram https://www.wut.de/e-8wwww-16-apus-000.php with the signals and the directions.

    You said:
    Pin 3 (plotter) = -20, relative to 5
    Pin 7(plotter) = 20, relative to 5

    So, here, under the Figure 2, there is a piece of paper with a null modem cable for a DB-9 that uses ALL of the signals.

    Anyway, if there is -20 V (A large voltage) on the PC side on pin #3 relative to pin 5 then you definitely need a Null Modem cable.
    Because Both PC and Plotter can't be putting out a voltage on the same pin.
     
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  9. BryWY

    BryWY Member

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    so pin 7 from plotter has +20 where does it go

    Same with blue from pc -20?


    do they go togethr cause diagram doesn't show that....
     
    Last edited: Apr 7, 2016
  10. BryWY

    BryWY Member

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    OK This did NOT work Help!
     
  11. BryWY

    BryWY Member

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    Shows up in production manager then disappears like before
     
  12. BryWY

    BryWY Member

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    I am starting to panic Ive gotta get this working before next week....Can anyone help???

    I am going to slice up a new serial straight cable....
     
  13. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    That basically say you need a null modem cable.

    The left pin is one connector and the right pin is on the other connector.

    5 to 5 (SG)

    2 to 3 TX/RX no particular order
    3 to 2

    This is the absolute minimum required.

    7 to 8 CTS/RTS no particular order
    8 to 7

    these pins usually implement hardware flow control

    4 to 6 (DTS/DSR)
    6 to 4

    Most of the time these signals are not used

    A jumper from 6 to 1 on the same connector should not be required.
    This jumps carrier detect from a true modem.

    This is a better description: https://www.decisivetactics.com/sup...r-null-modem-vs-straight-through-serial-cable


    The above has to work. Watch the pin numbers.
     
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  14. BryWY

    BryWY Member

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    WILL START OVER WITH A BRAND NEW CABLE HERE ARE THE COLORS WITH PIN ASSIGNMENTS

    1BRN
    2RED
    3ORANGE
    4YELLOW
    5GREEN
    6BLUE
    7PURPLE
    8GREY
    9BLACK
     
  15. BryWY

    BryWY Member

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    No sir tried everything job goes into production manager then disappears what could be so special about that cable?
     
  16. BryWY

    BryWY Member

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    well tried both wiring configurations neither one worked I am desperate have a trade show coming up. I need to get this working. going to try rolling back to earlier version of software on an xp system was using Flexi 10.1 on vista will go back to Flexi 8.1 anyone has any other ideas don't hesitate to post...I feel I am grasping at straws now. Will order the correct cable along with usb conversion next week. will post an update ...not much info out there about this particular piece of equipment.
     
  17. Les Jones

    Les Jones Well-Known Member

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    This is a summary of the information we have so far.
    Original cable

    PC end (Female.)


    1 (DCD) (in) Brown
    2 (RX) (in) Red
    3 (TX) (out) Yellow
    4 (DTR) (out) Brown
    5 (SG) Green
    6 (DSR) (in) Brown
    7 (RTS) (out) Blue
    8 (CTS) (in) White
    9 (RI) Not used

    DTR is linked to DCD and DSR (Brown wire.)




    ---------------------------------------------------------

    Plotter end (Male)

    1 (DCD) (in)
    2 (RX) (in) Yellow ?
    3 (TX) (out) Red ? (- Ve)
    4 (DTR) (out) ( ???)
    5 (SG) Green ?
    6 (DSR) (in)
    7 (RTS) (out) (+ve)
    8 (CTS) (in)
    9 (RI) Not used

    ---------------------------------------------------------
    As DTR, DCD and DSR are linked together at the PC end we know it is not a standard null modem cable.


    More clues would be helpful.
    Looking at the cable side of the male connector that was on the plotter end of the cable are there any pins linked together ? Are there any pins that have NOT had wires soldered to them ?
    Is there any voltage (+ or -) on these pins of the connector on the plotter. 1, 4, 6, or 8 Even a very small voltage would indicate that there was hardware on the plotter to use that pin as an input. (But it still may not be used by the software.

    Les.
     
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  18. granddad

    granddad Active Member

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    brywy I feel your pain, when I worked on old serial stuff I had a RS232 breakout box, and a few m/m & f/f, 9 and 25 pin D connectors and cables , any chance you can get hold of one will save all the soldering etc. I seem to remember plotters ( we looked after calcomp ) were an odd RS232 breed .
     
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  19. BryWY

    BryWY Member

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    I seem to remember a red wire running across the top of the pins
     
  20. Les Jones

    Les Jones Well-Known Member

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    This advert for a cable to suit your plotter says that it is not a standard cable. See the part that says "Important note"

    Les.
     
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  21. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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