Please..help me about communication between S7 1200 and inverter by MODBUS RTU RS485

[keithkyll]

If it's busy, then I suspect you have a connection problem. Try a read command first, like Kalle said. Check wiring. Check LEDs on the CM1241. Are transmit and receive both flashing when you send a command?

Look at this video from Youtube.

 

[danw]

We must proceed step by step here:

Kalle,

How true. Always validate read functionality before going onto write functions.

I'm laughing because whenever I make the equivalent statement I'm thinking to myself "Baby Steps", in homage to Dr. Leo Marvin's book (fictional movie book and character) in the What About Bob movie (1991) with Bill Murray and Richard Dreyfuss.

I couldn't resist.

Dan

 

[nguyenxuanphu]

Thank you very much...to all this forum !

Finally ....I could read and write from my VFD and power meter by modbus !

My problem was :wrong wiring from DP9 pin out (3 and 8 ), next dont put the first scan bit for REQ from MB COM LOAD DB (as Mr Keithkyll said) , at last Put wrong DB point to DATA PTR ....


Thank you again !

 

[KalleOlsen]

Kalle,
...
I couldn't resist.

Dan

And some of the threads here makes me thinking about Henry in 'There's a hole in the bucket'

https://www.youtube.com/watch?v=yD-ffhvefsw

Kalle

 

[danw]

My problem was :wrong wiring from DP9 pin out (3 and 8 ), next dont put the first scan bit for REQ from MB COM LOAD DB (as Mr Keithkyll said) , at last Put wrong DB point to DATA PTR ....

Thank you for telling the forum those things that were roadblocks. That helps others who find and this thread.

 

[danatomega]

And some of the threads here makes me thinking about Henry in 'There's a hole in the bucket'

https://www.youtube.com/watch?v=yD-ffhvefsw

Kalle

That is precious! The epitome of some of the threads here!