Serial RS485 communication confusing

Hello fellow PLC programmers,

I am having a hard time figuring out how to implement rs485 serial communication with an exisiting very old system. I received some documentation that explains how the strings the system expects must look like:

https://preview.redd.it/ep74k29e11bf1.png?width=805&format=png&auto=webp&s=0c57948d4ade361fbb1e00eaabed842667a349a7

I wrote some code to build the string with dummy data for the analogue data string:

https://preview.redd.it/zs3ad4i1f1bf1.png?width=799&format=png&auto=webp&s=95fbc5c8d0f47f0010c5ff9611b89149b6316704

Which outputs the following string: '@60:+1000,+500,+500,+500,+500,+500,+500,+500,+500,+500,<CR LF>'

for the digital string:

https://preview.redd.it/3zv66698f1bf1.png?width=595&format=png&auto=webp&s=dce5e5f58aa1f18a1bdef3eb878c9d1192caa72a

Which produces: '*61:$90$03$02$00$0E$00AA<CR LF>'

Is this right? Is <CR LF> supposed to be send like this?

Posted Jul 5, 2025, 11:45 AM UTC

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