Pixsys Forum

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

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

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

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)

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.

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: 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

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

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"

I resend you my application test.

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

Try with this LogicLab project

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.

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

My version of LogicLab is : 3.16.0.14

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

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.

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

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.

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

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

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.