Dear all,

in my recent project I have to communicate with 11 (different)Mobus slave devices. Before I was using Modbus but now, considering number of devivec, i would like to have some kind of for loop which will pass all slaves.

My idea is to have just one call of MB_MASTER block. Therefore, in resepect of current slave device, I need to change (among others) a DATA_PTR. Well there I have problem becasue DATA_PTR is VARIANT data type and I don't any (more) ideas how to solve that.

Is there any (elegant) way to do this?

Regards

Alen

Hello,

I'm facing same situation.

Have you solved it?

Hello,

if I understand your question, imagine that you have 11 Modbus slave devices, create separate 11 Data blocks "a DB for each slave" and take care for the symbolic check.

And imagine that you will read a REAL value, create a REAL data type inside each DB, and configure for each MB_MASTER --> DATA_PTR to the new created in each DB.

Hello,

the idea is to use one MB_MASTER and then change its input parameters depending on different conditions.

For de MB_ADDR, DATA_ADDR and DATA_LEN there is no problem because i set up an intermediate variable and then I move a diferent values there.

For DATA_PTR I don't know how to manage it.

Thank you

Yes, the MB_MASTER block will be repeated.

when you have 11 Modbus slaves, and for example you will read one value from each slave, you will have 11 MB_MASTER blocks.

and when the first MB_MASTER DONE bit is set, the second MB_MASTER block will be executed once a positive edge scan is sensed a 0->1 for the first MB_MASTER block DONE bit and so on.

Regarding DATA_PTR, as I told you, reference each MB_MASTER a separate DB and configure the DATA_PTR to point into each DB.

Thank you Abdel.

I'll try to make MB_MASTER call for each slave.

In any case, I wonder if is possible to "dinamically" change DATA_PTR to point other DBs.

What do you think?

Yes, you can.

one of my projects has 25 Modbus slaves, and I issued a MB_MASTER for each slave at least 6 times.

25*6= 150 MB_MASTER blocks are used.

So, don't worry, but make sure to uncheck the symbolic from the properties from each DB.

and remember the Modbus RTU half duplex, one device can use the media so don't call a new MB_MASTER unless the previous is executed.

Hello,

you can also look here on forum for other examples or user projects/Solutions. I think you'll find something useful in other hand, to Abdel's useful help.

Thank you!

Just one hint, when using several MB_MASTER calls it is important to take care of EN and REQ inputs because only the MB_MASTER call that is requested by REQ should have EN input enabled, the others should have EN disabled.