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Click to Click Communications Serial Using Port 2

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  • Click to Click Communications Serial Using Port 2

    I have two click CPU's. Neither have RS-485 and neither have Ethernet. I want to connect them together using Port 2. My question is....... Can this be done(I think it can) and what would the cable look like? Would the cable just swap the RX and TX. Just want to share I/O. I am doing a small test and do not have enough I/O on a single click. Don't want to purchase more hardware when I can just use another click as remote i/o. Speed is not an issue. Very slow process.

  • #2
    Never done it. Maybe through Modbus reads and writes?
    Why worry? If you've done the best you can, worrying won't make it any better

    - Walt Disney


    • #3
      You will want to set up a ladder program in the 2nd Click that maps all your used X's to a single word or double word. Same with your Y's. A normal word would let you map 16 X's to it. Then use a modbus read on the main Click to pull the data in an alternating fashion. So initiate the read of the X word(s) and when it completes used that bit to start the read of the Y word(s) and then back around again. It should be very easy to do as long as the Clicks can act as a Master and Slave properly through port 2. Looking at the specs of the "Click Basic" which I assume you have since it is the one without Ethernet or RS-485, it looks like the ports both support master/slave type.

      edit: or as long as the words the X's and Y's are mapped into by bdefault in the click are readable by modbus then once you look up those memory addresses you shouldnt need to know or do anything else, just read those addresses from the main PLC and output the data to a new memory address for you to use.
      Last edited by MikeN; 10-02-2019, 11:57 AM.


      • #4
        Looks like it's on YouTube with an explanation. However, combo expansion modules are cheaper than a second PLC, and easier to program.


        • #5
          Agreed that modules are cheaper. I already have the 2nd PLC. It's not permanant. Just wanna do something for a bench test and need more I/O. Won't be used long.

          Can anybody confirm the swap of the rx/tx wires? Need to get a cable done. Or would an HMI cable do. C-More Micro to be exact.

          By the way, the Youtube video was very helpful. It is exactly what I am doing.


          • #6
            Wires should swap. Micro cable might work. I don't have time to track down the pinouts right now though to verify.
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            • #7
              There are threads and some simple examples of this idea on this forum

              (photobucket has decided to go sideways on me since that post- I cannot play the video anymore)
              (this example is RS-485)

              (this example is RS-485 so ignore any signal connection info)

              My usual practice is to make two single-headed cables and then connect the RX/TX GND to a 3-pos screw terminals so that I can get the RX/TX conection correct, them make a purpose-built cable.
              Last edited by kewakl; 10-02-2019, 01:46 PM.


              • #8
                Pulled the Pin Out for a DV1000CBL. The youtube video is exactly what I am doing....again for a proof of concept and I have the hardware. I will try and post whether or not the cable works. With the DV100CBL the RX and TX swap. In fact all pins swap. Either way, it is modbus just like communicating to a C-more Micro or anything else Modbus RS-232.


                • #9
                  I have found that when using the Click PLC with multiple read and write instructions on the network, it is best to set the timing with a shift register.
                  The example is in the following post.
                  Here is the link to the Click PLC program. This program will communicate with a solo process temperature controller.
                  Hope this helps you out.
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                  • #10
                    cross wires 3 and 4 and connect wire 6 to ground


                    • #11
                      Thanks for the help. This should work. I have done some modbus messaging before using the RS-485 port thru and ethernet convertor and thru and ethernet radio. Then read it on the other end back thru the radio, thru the ethernet convertor and thru the RS-485 port. These don't have that port.