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How to send a string through RS485? JZ10

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I am trying to create a program that will, allow to read Output, Input, Analog statuses and also Enable/Disable Outputs. I have a working program created and it works very well through RS232, however I need to use RS485.

My problem is that I can send data through RS485, but i cannot receive. For example by sending the characters through RS485 "OS" the PLC gets the request but replies through RS232 not RS485.

P.S. By sending the characters "OS" I should get a reply that displays all the Output Statuses.


I have added my program in the attachment.

PLC Projekts.U90

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  • MVP 2022

A quick look at this and for starters I'd fix all your Input Status Determine inputs......they are all the same......Input 0.

As for your comms woes, are you using an MJ20-RS?     If not, you should be.   It is possible that your 485 sends are being interpreted on the 232 input of an MJ20-PRG, but it cannot send on 485.  I suggest you have a good read of the various Help files.....Com Port Mode: RS232/RS485 etc

You should initially be just trying out what you want to do on just one I/O, testing this thoroughly until it all works correctly and you understand it completely, then progressively add in other additions you want, testing along the way.

cheers, Aus

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