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    A Bit Stuck on Writing Multiple MODBUS Registers

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    • danD
      dan
      last edited by

      Then this one
      0_1595286068497_73127f3f-7d6d-4ea2-8866-f7ef9d41c2e9-image.png

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      • MattFoxM
        MattFox
        last edited by

        does 0x02 not work? it's asking for a string as well... is the datatype not an integer?

        Do not follow where the path may lead; go instead where there is no path.
        And leave a trail - Muriel Strode

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        • danD
          dan
          last edited by

          I think it's wanting '2' then '35702' written into 4104 and 4105 respectively, both at once using function 16 multiple write.
          Here's an excerpt from the manual for what they're getting at..

          1. One of the system control keys from the table below must be written into register 8 and its ones-compliment written into register 9
            with a single function 16 (write multiple registers) to perform the specified system control function.
          2. Writing any other value or using a function that is not available will return extended exception code 7 (Illegal value written to
            register) and have no affect.

          The table looks like this..

          0_1595286481588_b9c7913d-9d8b-478f-9775-86930d8dfaee-image.png

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          • MattFoxM
            MattFox
            last edited by

            @dan said in A Bit Stuck on Writing Multiple MODBUS Registers:

            35702

            I've entered it in like this since the values are a different length:
            0_1595287109290_eb9a056b-f56d-45ef-a15e-45e47614572e-image.png

            Do not follow where the path may lead; go instead where there is no path.
            And leave a trail - Muriel Strode

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            • danD
              dan
              last edited by

              Oh, that makes more sense :)
              I'll try that, thanks heaps.

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              • danD
                dan
                last edited by

                0_1595287296908_f92e2f99-755e-4905-be74-6df858320823-image.png

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                • MattFoxM
                  MattFox
                  last edited by

                  That doesn't give you much to work with does it??
                  0_1595288458427_0a3e4d6b-b8a8-4d6b-8b1d-9834705a4b87-image.png

                  I got this working!

                  Do not follow where the path may lead; go instead where there is no path.
                  And leave a trail - Muriel Strode

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                  • danD
                    dan
                    last edited by

                    oh yeh, that's interesting, I'll try the coils.

                    Cheers for that hey.

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                    • danD
                      dan
                      last edited by

                      FML...

                      0_1595288851390_73c615ec-36ee-4aab-9c39-7de2ee65a439-image.png

                      It does say Control Registers at the top of the info page..

                      0_1595288918666_7ee37d3f-d806-4d64-9007-bc9a9ebe60b4-image.png

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                      • MattFoxM
                        MattFox
                        last edited by MattFox

                        So it's a nope? - note your 0x2 should be 0x02

                        Do not follow where the path may lead; go instead where there is no path.
                        And leave a trail - Muriel Strode

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                        • danD
                          dan
                          last edited by

                          Na I don't think I can write to coils on this device.

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                          • MattFoxM
                            MattFox
                            last edited by

                            write
                            4104
                            0
                            2
                            ASCII
                            0x8B76,0x8B76
                            That sets that control key and calls function 2

                            Do not follow where the path may lead; go instead where there is no path.
                            And leave a trail - Muriel Strode

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                            • CraigWebC
                              CraigWeb
                              last edited by

                              Hi Dan

                              Ive run into similar situations before with modbus device.
                              Make sure your data source has Use multiple write commands only checked.
                              Modbus function 16 writes to holding registers
                              Use a 4 byte unsigned int.
                              I believe the decimal number would be 166774:
                              0_1595311234142_Screenshot 2020-07-21 at 08.00.25.png
                              Turn on the log I/O of the data source so you can inspect the modbus commands.
                              There may be a chance you might need to use a 4 byte unsigned int swapped

                              If you dont come right paste your I/O commands here.

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                              • danD
                                dan
                                last edited by

                                Hi Craig, I've definitely got multiple writes selected in the data source.

                                I might have to re-visit the calculator / converter looking at that number. I was just sending it the raw hex value.

                                I'll give it a go. Thanks :)

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                                • CraigWebC
                                  CraigWeb
                                  last edited by CraigWeb

                                  Hey Dan

                                  Did a quick tet for you. I believe it is correct checkout the snapshot I took from Wireshark:
                                  0_1595326095916_Screenshot 2020-07-21 at 12.07.11.png

                                  Something to note about modbus is that sometime in manuals they will prefix the register number with the register type. Holding register is decimal 4. So when you see that on a manual you will just put offset 104 in mango. You will also see that some manual are 0 based and some are 1 based. So you might need to try 103 instead of 104.
                                  Below is the settings I used for my point. I used decimal 166774
                                  0_1595326337152_Screenshot 2020-07-21 at 12.12.05.png

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                                  • MattFoxM
                                    MattFox
                                    last edited by

                                    Ok, so I can understand using 166774 gives you 0x00028b76, basically just bit shifts the entire thing in. And that by using a holding register implicitly puts a 4 in the front so only 104 is needed... But if the manual states you need a control key into 8 and its 1's complement into register 9, shouldn't it be 0x8B768B76 = 2339801974 DEC?

                                    Fox

                                    Do not follow where the path may lead; go instead where there is no path.
                                    And leave a trail - Muriel Strode

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                                    • danD
                                      dan
                                      last edited by

                                      OK, now my brain is really hurting, I'll turn on the i/o log and see what mine is outputting.
                                      Just to clarify a little further, the MODBUS register I need to write to is on 'Page 16', the manual says to multiply 256 x Page then add the Offset, so in this case I'm on (256 x 16) + 8 = 4104
                                      When reading off battery voltages and other engine diagnostics off this the formula seems to work.
                                      I'll try again with the decimal.

                                      Cheers

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                                      • danD
                                        dan
                                        last edited by

                                        0_1595368234133_6f692b3b-5b32-4e53-8adc-08c5a7ab46a9-image.png
                                        0_1595368250040_9530b480-46fd-4685-869a-41c8aebbf8c0-image.png

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                                        • danD
                                          dan
                                          last edited by

                                          Interestingly, when I write the hex values I get this pop up error..
                                          0_1595368403070_8b8aefed-818b-4048-850e-4e56afa9c2a3-image.png
                                          Nothing written in the log during this time however :/
                                          0_1595368421016_04c99fc6-f9b1-47b1-9109-ffaa4b0fe395-image.png

                                          cwangvC 1 Reply Last reply Reply Quote 0
                                          • cwangvC
                                            cwangv @dan
                                            last edited by

                                            @dan
                                            just curious why the 'Number of registers' is '0'? shouldn't be at least '1'?

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