MODBUS RTU SLAVE FOR CP340 (NO DONGLE REQUIRED)

Hello!

Mr. TIBI68, could you make special version of your library to call SFB58/59 instead of SFB52/53. A have an ancient s7-300, which doesn't support nowadays P_SEND and P_RCV functions.

Best regards,

Dmitry Konstantinov

 Dear,

I have used this block to read 100 holding registers. Initially Data seen on Modscan. But after some time Modscan shown Invalid Response to query and only Rx led glowing on CP340. I have checked all settings in Modscan but I am not sure what is wrong.

Please help....

Hi,

did you tried to restart the Modscan, remove the cable and plug it back or reset the CPU?

If it was working before it would be interesting why it stopped.

Did you made any changes somewhere or was it out of a sudden?

You wrote that Modscan is giving message for invalid response, how is that possible without any Tx LED lit on the CP?

The Modscan has an option to show the actual traffic between the devices.

Maybe you can upload a screenshot.

At the CP the databits should be set to 8 on the interface parameter.

Good Luck!

Do you have any function block for CP341 Modbus slave RS485 protocol RTU?

Thanks man,

Hopling

Hey TIBI, I want to inform you that everything is fine with your MBSL341 FB. I just tested it - working perfect! :D

P.S.

You didn't add FB7 and FB8 in project you attached to last message. FB37 MBSL341 doesn't compiling without it. For me it was not a problem to understand that. But it can be difficult for beginners to find out what's wrong, I guess.

My FB 7, FB8 version is newer than yours so FB37 error when compile. Could you please share your FB7, FB8 with correct version you're using to run FB37

Me too: time stamp is different for FB 7, FB 8 (different version). So FB37 can't run

Please help me to solve this problem.

Dear TIB68,

many times CP340 stops giving data to master.

PLC has to be reset to solve this problem. Is there any solution to avoid PLC reseting. Can i use init bit of block to reset or any other internal reset of blocks (P_SEND_R OR P_RCV_R). The system is 300 R so whenever CPU changeover happens this issue arises.

Thanks in advance for your efforts.

I have no experience with software redundancy.

You might find some help in the documentation about the software redundancy.

Maybe there are some settings you need to take care about when using it together with CP340/CP341.

Sorry that I cannot give you more help.

I am not aware of a reset function for the standard blocks.

Best Regards.

EDIT:

I found an interesting previous post in the following link:

https://support.industry.siemens.com/tf/ww/en/posts/using-cp341-in-s7-300-soft-redundancy/96658?page=0&pageSize=10

There was no solution mentioned how to fix it but maybe you can ask the initiator if he found a solution for this problem in the meantime.

Best Regards.

TIBI68

Hi,

did you tried to restart the Modscan, remove the cable and plug it back or reset the CPU?

If it was working before it would be interesting why it stopped.

Did you made any changes somewhere or was it out of a sudden?

You wrote that Modscan is giving message for invalid response, how is that possible without any Tx LED lit on the CP?

The Modscan has an option to show the actual traffic between the devices.

Maybe you can upload a screenshot.

At the CP the databits should be set to 8 on the interface parameter.

Good Luck!

 HI,

Same Problem I faced. I copied FB7 and FB8 from modbus library MBMA341.

after that It is working fine. superb !!!!!!!

Thanks a lot.