How to build this cable?

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  • September 22, 2011 at 4:35 pm #2633
    JM K
    Participant

    Hi,

    I am trying to build a cable to utilize the serial port (RS-232) on the CDP Unit. The cable provided with the CDP is a 9 Pin DB Male / Female. The problem is that I am trying to establish serial communication (RS-232 and Modbus) with a PLC that has a 9 Pin DB Female on one end and an RJ11 on the other end. I think I would have to build a DB 9 Pin Male / Male configuration cable. Is this possible? If possible what would be the pin out for such a cable? I would very much appreciate it if someone could answer my questions and if possible provide me a pin out for such a cable. Thank you very much.

    Best Regards,

    JM

    September 22, 2011 at 5:18 pm #3379
    Lonny Knudson
    Blocked

    Hi JM,

    It is possible to build the cable that you need, however we can’t suggest a pinout without knowing how the connector on the PLC is wired. In your support portal case we posted a diagram showing how the DB9 on the CDP is wired. You will need to have the same information for the connector on the PLC to determine the correct pinout for the cable.

    The serial interface on the CDP is a DCE device with standard pin assignments. If the PLC also has a standard DCE interface you can use what’s called a ‘null modem’ or ‘crossover’ cable. If the PLC is a standard DTE interface you can use a ‘straight’ cable (pin 1 wired to pin 1, pin 2 wired to pin 2, etc…). Both of these types of cables you should be able to buy pre-made. If the PLC uses non-standard pin assignments you are more likely to need to build your own cable.

    September 22, 2011 at 5:52 pm #3380
    JM K
    Participant

    Dear Lonny,

    thank you very much for the response. The PLC is a standard DTE interface with the following pin out on the serial interface:

    Pin # Description

    1 RS232 Power in

    2 GND

    3 TXD

    4 RXD

    5 GND

    6 RS232 Power in

    Input voltage range 5-15V (RS232 positive voltage)

    I think it could be possible to construct my own cable, yes? I am a bit confused about the RS232 power pins on the schematic of the CDP that I received yesterday. Thanks again for your help. I would appreciate it if you could let me know any suggestions on the pin out for the new cable.

    Best Regards,

    JM

    September 22, 2011 at 8:47 pm #3381
    JM K
    Participant

    Hi Lonny,

    I apologize for complicating such a trivial problem. I think I have it all figured out. Thanks for your help.

    Best Regards,

    JM

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