Not at all Duris. I am glad you responded. Just i dont know how to develop the RTU frame in PLC TCP communication. Is there any guide to learn that.

Thanks,

Jay

Duris_I

Hello Jay,

hope not problem answer to you here instead of Milos. You need implement only RTU format inside your PLC TCP communication, nothing more. In other details (maybe about count checksum,...) you can also fins help on web. Of course, if Milos will be kind give you his example or pictures from his code...

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Split from Connect EKI-1521 Gateway module with S7-1500 over ethernet.

Hello again!

I was using blocks TSEND_C and TRCV_C, not MB_CLIENT. Those blocks have parameter DATA, this is location of data to be sent or where to receive data. Please see attached pictures and everything will be clear.

You receive data in MyDB.MyRcv array. Here you must identify RTU frame and extract data from it. RTU frame should look like this for example: https://www.picotech.com/library/oscilloscopes/modbus-serial-protocol-decoding

If you are creating requests toward serial device one important thing is to, inside RTU frame, create CRC (cyclic redundancy check) bytes. If these are not correct serial device will not reply to you.

If you have any other questions please contact me.

Milos

 Thanks Milos for sharing the info with me. I will look into it and see what i can achieve. First thing is that decoding like Duris and you suggested. If I can get through it, then everything else will come together automatically.

Thanks,

Jay

Milos Petrovic

Hello again!

I was using blocks TSEND_C and TRCV_C, not MB_CLIENT. Those blocks have parameter DATA, this is location of data to be sent or where to receive data. Please see attached pictures and everything will be clear.

You receive data in MyDB.MyRcv array. Here you must identify RTU frame and extract data from it. RTU frame should look like this for example: https://www.picotech.com/library/oscilloscopes/modbus-serial-protocol-decoding

If you are creating requests toward serial device one important thing is to, inside RTU frame, create CRC (cyclic redundancy check) bytes. If these are not correct serial device will not reply to you.

If you have any other questions please contact me.

Milos

Dear Jay,

just read your conversation.

I believe that if you want to send MB-RTU over TCP you will at the device side convert the MB-TCP to serial, am I right?

In that case I would not bother with the RTU programming and get a MB-TCP to MB-RTU gateway like this one.

https://www.lantronix.com/products/xpress-dr-xpress-dr-iap/#tab-overview

Or a profibus to modbus gateway if you have a DP port on your CPU..

https://www.hilscher.com/products/product-groups/gateways/for-the-control-cabinet-ip20/entry-level-gateways/nt-50-dp-rsdpsmbr/

Or in case you have to program it your own this document will support you. It has even a code for the CRC16 calculation, just need to adapt it for S7.

http://modbus.org/docs/PI_MBUS_300.pdf

Good Luck  

Best Regards.

 Thanks TIBI for the suggestions. I already have the gateway and with the help of Duris, I made it work. Thanks again for all the valuable inputs.

Thanks,

jay

TIBI68

Dear Jay,

just read your conversation.

I believe that if you want to send MB-RTU over TCP you will at the device side convert the MB-TCP to serial, am I right?

In that case I would not bother with the RTU programming and get a MB-TCP to MB-RTU gateway like this one.

https://www.lantronix.com/products/xpress-dr-xpress-dr-iap/#tab-overview

Or a profibus to modbus gateway if you have a DP port on your CPU..

https://www.hilscher.com/products/product-groups/gateways/for-the-control-cabinet-ip20/entry-level-gateways/nt-50-dp-rsdpsmbr/

Or in case you have to program it your own this document will support you. It has even a code for the CRC16 calculation, just need to adapt it for S7.

http://modbus.org/docs/PI_MBUS_300.pdf

Good Luck  

Best Regards.