dealing with modbus

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Thread Starter

boyd

hi all

first time here glad i found the site.

my problem;
i need to learn protocol for modbus how to read, write and understand. the ins and outs of making a daisy chain.

i have been building machinery for some time with the vendor specifying what i needed to use to do what i needed to do. once they got all the pieces working all i had to do was assemble.

working on a new piece and the existing equipment we used was to big hence miniaturizing came to pass. since i'm not buying all the parts from one vendor, i have found i really need to know how to really work in modbus. i need to learn protocol for modbus, how to read, write and understand. the ins and outs of making a daisy chain
since all vendors blame the other part (not theirs)

so my question where do i start
 
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You're in luck -- Modbus documentation is VERY plentiful and usually, free!

First, you can download the official protocol specification from Modbus.org, which I believe is free.

Then, tutorials on request and response framing are on many manufacturers' websites.

And finally, there are numerous free and inexpensive utilities that you can use on the other end of the wire from your implementation to test compatibility.
 
yes nomenclature is very important. i tried to send a picture of what i made to talk to several slaves. it had a total of 4 drops 1- master DB9, 1- slave DB9 and 2 - rj45's the vendors of each piece said it was either my cable or the part they did not sell. so i wanted to see the correct to make the drops. (note it was not the cables problem) hmi was written to several address and the new product i used to replace on old one had different ones. once resolved we are gold. thanks to all who posted i am one who really appreciate the help and will be here for ever learning what the vendor won't teach. awesome forum.
 
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