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Labview+modbus+USB-485 device

We are using labview to creat a project and try to collect instrument data through a USB to RS485 converter over modbus RTU. At present, we found a strange phenomenon. When we use the converter of USB devlice with the built-in CP210 chip(Silicon Labs'), the modbus cannot be connected, but it can be connected through the serial port debugging assistant software. At first, I thought that the project was wrong or the version of NI modbus library was wrong, but find nothing ,and then we try to use the RS232 of the PC and then transferred the RS232 to the RS485 device, but it still couldn't communicate. In all cases, it is possible to communicate normally through the modbus serial debugging assistant. Until the end we found that when we changed the CP210 device to use the converter with the built-in CH340 chip, we found that the problem disappeared. 

 

I don't know if someone else has encountered similar problems, and if there is any way to solve them.

 
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I don't really understand your question but I have done several Modbus based LabVIEW projects using a "Ulinx" 485USBTB-2W from B&B and they work flawlessly 

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Unfortunately, most readers of this Forum, including some real Experts, have not mastered the skill of being able to read the code that Posters fail to post. If we cannot see "what you did wrong", we are unable to tell you how to fix it. (Bob Schor 28 August 2018)
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We have three ways to use RS485, 

One is through the computer's own RS232 plus an RS232 to RS485 adapter。

The second is the converter that converts USB to RS485, and the chip used in the converter is CH340。

The third type is the converter that converts USB to RS485, and the chip used in the converter is CP210。

 

All three methods can use RS485 communication through other programs.

But only the second method(CH340) can connect RS485 via labview's modbus library project 。

 

I don't know if someone else has encountered similar problems, and if there is any way to solve them.

 

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@epmtech wrote:

We have three ways to use RS485, 

One is through the computer's own RS232 plus an RS232 to RS485 adapter。

The second is the converter that converts USB to RS485, and the chip used in the converter is CH340。

The third type is the converter that converts USB to RS485, and the chip used in the converter is CP210。

 

All three methods can use RS485 communication through other programs.

But only the second method(CH340) can connect RS485 via labview's modbus library project 。

 

I don't know if someone else has encountered similar problems, and if there is any way to solve them.

 


 

Sounds like a configuration issue, as all these devices (except for the one that uses an actual serial port) probably install a virtual serial port.

 

So from a LabVIEW programming aspect they are all the same.

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Unfortunately, most readers of this Forum, including some real Experts, have not mastered the skill of being able to read the code that Posters fail to post. If we cannot see "what you did wrong", we are unable to tell you how to fix it. (Bob Schor 28 August 2018)
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