RS485 communication useing Modbus master

[senthilg]

Hi,

This is senthil. I do the program in LabVIEW for modbus RS485 communication. I use LabVIEW 2012 full development system. i also install modbus master from VIPM. I did the program using Modbus master. I using read holding register to read the data. But in excution time data didn't show.

[Jordan Kuehn]

Do you happen to have a 3rd party piece of software to confirm your configuration settings and connectivity? What hardware are you using for RS-485? That's not a standard serial port on most machines (not that even RS-232 is all that common these days either...).

[senthilg]

hi

I use rs485 to USB converter. make B&B electronics. 

[ensegre]

it looks wrong from scratch that you're repeatedly initializing and closing the port in a full throttled loop. Anyway, first things first, not knowing what your device is, and whether the communication parameters and the register address are the right ones, there is little we can say beyond "ah, it doesn't work". It might even be that you didn't wire the device correctly. Is that 2 wire RS485 or 4? Are you positive about polarities? Do the VIs give some error?

[Porter]

Hello Senthil,

I would recommend trying the "MB_Master Comm Tester" (you can find this in LabVIEW's example finder) to test the communication with the device. This way you can just focus on the testing the serial port settings and register addresses before writing your own code.

[senthilg]

hi,

 i use schneider electric energy meter Model:EM:1200. which is come with RS485 communication port. my program is to read the power and power factor using RS485 communication in LabVIEW. I try to program using modbus master, but values didn't shown. please help me.

[ensegre]

If it is this one, you could test communications first with their software, as per page 46 of the manual, to exclude that you have wired the interface incorrectly, or that the usb dongle is defective.

[senthilg]

hi, 

i tested with their software it working correctly with same usb. but i labview it did't work why.

[ensegre]

Provided that the communication parameters are correct, probably you should initialize once, read no too often and close only when you're really done. Trying to do that 10000 times per second usually impedes communication.

[senthilg]

i get error as "Modbus CRC\LRC error".

[Porter]

Please try like this:

Note that the default baud rate for the EM1200 is 19200 bps.

Also note the 250ms delay between polls.

[senthilg]

hello,

thank you for your help. i got the output.

[Engr Naveed]

On 8/1/2017 at 7:19 PM, Porter said:

Please try like this:

Note that the default baud rate for the EM1200 is 19200 bps.

Also note the 250ms delay between polls.

Hi Porter can you share your email on my email address ( naveedeng1@gmail.com )