[TD700] Use as Modbus Master

[user10683]

Hi,

My company bought a TD700 and we are trying to use its Modbus Master to read and write values with a Danfoss PLC (MCX).
Everything is OK I can read and write values but is it possible to create an edit field that can read an Modbus address on the danfoss PLC and write the same address ?
It seems that we need to create two variables in LogicLab one for reading and another for writing so in a edit field if I put the writing variable, if I change the setting on the danfoss PLC the writing variable is not updated

Eric

[Pixsys tecnico 1]

Hi,
assign the same LogicLab variable as input and output to the same PLC address.

[user10683]

Re,

Is it possible to request grouped modbus addresses ?

I have a lot of Modbus addresses so I need to group requests otherwise the modbus will be saturated.

Eric

[Pixsys tecnico 1]

Hi,
you can group requests only with consecutively Modbus addresses using. For example,
if you add FC-03 function, you have to insert start address, then using ADD button you can add different address to reach with the same request (see attached image)

Immagine.png

[user10683]

Hi,

OK I found how to do but I have a very BIG PROBLEM !

Modbus with a single PLC works very well but I have a big problem when 2 PLC's are connected to the same modbus network !

PLC 1 : modbus address 1
PLC 2 : modbus address 2

Modbus com : 19200 / RS485 / 8N1

Only one is working at the same time !

If I disconnect the first connector of the first PLC the second one starts to work adn vice-versa

Just a precision : my Modbus network works very well when I test with the software Modscan (I disconnect the connector on the TD700 and put it on my RS485 usb key).

I need a fast answer it is very important.

[Pixsys tecnico 1]

Hi,
I cannot see if slave devices are good because they are custom and I do not have the PCT file. However, are you sure to have set slave 1 and salve 2 with different node number and different address number? see attached picture:

Cattura.PNG

You must have MODBUS ADDRESS and NODE NUMBER equals for each PLC, so:
PLC1: MODBUS ADDRESS= 1 and NODE NUMBER =1
PLC2: MODBUS ADDRESS= 2 and NODE NUMBER =2

[user10683]

Sorry I send you a modified version my addresses are good when I test :

PLC1 : node number 1 modbus address 1
PLC2 : node number 2 modbus address 2

[Pixsys tecnico 1]

HI, send my the entire project and also your custom device file so I can check all.

You can get it there:
C:\Program Files\Pixsys PC Tools\Catalog\ModbusCustom\
it will be a file named as the device ".PCT"

[user10683]

I resend you my application test.

My PLC are now generic modbus devices but always the same issue.

[Pixsys tecnico 1]

Try with this LogicLab project

TestLogicLab.zip

[user10683]

I tried but always the same.

When I watch Node 1 and Node 2 sysMbMRtuNodeStatus I always have the PRES on FALSE on one PLC.

When I unplug the RS485 connector on the PLC with PRES on TRUE (the other PLC has PRES to FALSE), the PRES on the other PLC pass to TRUE.

[Pixsys tecnico 1]

Maybe is a software bug of an old release, what version of LogicLab do you have?

[user10683]

My version of LogicLab is : 3.16.0.14

[user10683]

Sorry but I don't know where to download LogicLab and PageLab ?

[user10683]

I found the last version 4.2.0.10 but always the same.

It is very very problematic

This is a very simple configuration and we change from CANOpen to modbus because CANOpen was problematic too so we need to find the bug.

[Pixsys tecnico 1]

With new version, create a new projetc instead of opening the old one.

[user10683]

It is what I did.

I did another test with IR33's of CAREL and always the same !
It is a little bit better because sometimes the seoncd one has PRES to TRUE but often passes to FALSE.

Single IR33 on the network works like a charm at modbus address 1 and 2.

Once together on the network only the first unit answers correctly the other has plenty of timeouts.

[user10683]

I did another test.

I created 2 slave devices with Modsim32 at address 1 and 2.
I connected my PC via RS485 usb to the TD700 and everything was OK (it is working like a charm no timeouts).

So there is a problem with my real network but I tested with Danfoss and CAREL devices it's the same problem !

But with Modscan32 my real network works like a charm too so I don't understand where is the problem

[Pixsys tecnico 1]

This morning I ware re-reading all messages to try to find where is the problem, I red:
"
When I unplug the RS485 connector on the PLC with PRES on TRUE (the other PLC has PRES to FALSE), the PRES on the other PLC pass to TRUE.
"

Normally this happens when the two devices have the same Address or timings are too much "short", so verify:
-slave addresses of the devices
-increase time out for esch devices to 5000mS
-increase time befor send to 20mS

[user10683]

Indeed I found the problem it was the "WAIT BEFORE SEND".

I changed everything except this parameter.
I put 300ms and everything works like a charm.

I am happy

Thank you.