Hello again,

i have established successfully a MODBUS communication between S71200 CPU1217 using CM1241 RS422/485 module and a NETWORK Analyzer instrument in order to read in my plc code values of voltage, current etc.

I have prepared PLC as Master and the Analyzer as slave = SLAVE1 with adress 31.

Now i need to communicate with 1 more slave let's name it SLAVE2 which is same device as SLAVE1.

I will set a different adress ( 32 ) and i need your suggestion, how to add this new communication to my existing attached code.

I need a new block like network 2 declaring the new connection details ?

Could you put 1 comment in each network about the add ons that i have to do ?

Th eproblem is that i have not the equipment available to make the simulation. I will test it on site.

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Split from Modbus RTU TIA PORTAL.

Hi Kosmous.

I previously made a library that address the challenge you describe.What is the name of the device you are communicating with? If your device is in the link bellow, then it should be pretty match strait forward to communicate with as many devices as you want:

https://github.com/rexhip/rexhip/tree/master/station%20blocks

If you would like to use the library, then I may help you to set it up. If you rather would like to modify your existing program, then I may also help you on that.

https://github.com/rexhip/rexhip

Kind regards

Dear ola84,

thanks for answering !

The slave device is ABB_m2m and is reffered in the list that you sent ( 4th ). How could we benefit from this ?

I already communicate with this device and i want to add a second same device in my network using the same method as my current code.

From the 2nd slave i need to read just one variable.

Do you think it is asy to add the second slave in my code ? Address of the second slave will be 33

1. Locate and expand «External soucre files» inside a PLC in the tree on the left.
2. Click «Add new external file».
3. Download the attachment, unpack and select it.
4. Right click the imported file and click «Generate blocks from source».

Hello ola84

great effort !

it seems to be the best solution especially when somebody have to communicate with more than 1 slaves. I will try it, but i can't test it before visitng the site.

Could you give me some advices, how to illustrate the connection with the 2nd slave using the "manually" method , as the attached file ?

For example, do i have to call again the communication blocks ?

If you could put a comment to each network, would help my effort !

I will try to prepare both solutions for safety.

Hi.

It actually just took me a few minutes to put the program together, so no worries. Keep in mind that the library require firmware >= 4.2. So if your plc doesn't have it, you should download it in advance. Also you need TIA portal >= v14.

A tip at site: In the attachment you may see the sb-variable inside each of the data blocks for the ABB-devices. If everything is okay then the done counter will be running and the comm and exception counter will stay still.

For your existing program you would need to extend the sequence with another step. In that step, the variable connected to mb_addr on mb_master, should be replaced by 32. It's similar to what you already  doing, by making two different queries to the same device, just now you would need to change the mb_addr variable.

If for some reason the library wouldn't work for you, then I can help you on your existing program.

Kind regards

Dear ola84,

i prepared attached the 2 last steps in order to read from the 2nd SLAVE address 32.

Could you check if i change correctly the adress to value 32 and then back to 31 in order to restart reading the 1st slave ?..may be i could make the transission back to adress 31 at Network 1 ?

As you said, the only value that have to be changed is the adress. All the other functions remain the same.

In the 1st post is attached the code until step 7 = reading from slave 1 in 7 steps

ola84

Hi Kosmous.

Your attachment look good to me. Change the mb_addr back to 31 in either network 17 or 4, should both give the same result. Remember to change your existing code so the new steps will be included in the sequence.

I believe your travel to site is quite far since you prepare so thoughtfully. May I ask from where in the world you are working? If you encounter a remaining bug at site I am sure you will solve it! :) But as said previously, I am know the library will work right away, so please use that if you struggle.

Kind regards

 Dear ola84,

the code with steps worked successfully !

In the near future i will update TIA Portal V13 SP1 to V14 and i will work the same application with the SCL library.

For somebody who needs to establish Modbus connection with 2 or more slaves the above code is working without problems. Hope to be helpful to somebody in the future.

** I'm working in Greece and the project is in Albania ( six hours by car ), so before a visit at site, everything must be tested !!

Thank you for your helpful suggestion