Communication between Labview and Controller via Modbus protocol

[Genjis5]

Hi,

I’m trying to create a testing environment for temperature and humidity with Labview. My problem is that I can’t communicate with the device which controls parameters. My equipment is the following:

-West 4400 ¼ Din Profile controller

-USB485ui serial adapter from Amplicon

Communication protocol is Modbus RTU. I tried to communicate and to send modbus command with Hyperterminal, Labview VIs (Looppack or Modbus pack) and others softwares but I can’t get any response from the device. Visa detects it on COM port. It seems that the device is connected but I must send bad commands to it. Is there any simple mean to chek that a modbus device is communicating ?

I’m just a beginner in modbus protocol so if someone could give me any help or advice, it would be great.

Thanks.

 

[Genjis5]

Hi,

I am now able to fully control the West device, but I am having some trouble when I try to add others slave devices. I am trying to control the environmental chamber and to read data from sensors simultaneously.

The two devices are communicating with Modbus RTU on the same serial RS485 port. I found that it is a common problem when you are connecting two slave devices on the same serial port. Timeout Error are occurring and it looks like the Labview serial function can’t read and write data on both devices at the same time. It works well in highlight or step mode but not in continuous mode.

Is it possible to connect two modbus devices on the same com port and to communicate with both on Labview ?

Many thanks