Rs485 communication

[Unitech Scales]

I want to Acquire data from a Power analiser having Rs-485 2-wire port. Rs232 to Rs485 converter is alos provided by the manufacturer it self. The system forks on Modbus RTU protocol. The Modbus protocol establishes the format for the master's Query by placing in the device address(01), a function code(04) Starting registr(0000), ending registry (0002)  and error checking field (CRC (71CB)). I tried to send the tata through Instrument asist Vi but i could not get reply. I tried  thriough serial visa read and write visa but i am unable to get the result. The RTU mode format is 9600,8,1,none.

Please help me in this regard

Regards

Prasanna Kumar N M

[unclebump]

Try the llb file at the end of this thread.

http://forums.ni.com/ni/board/message?board.id=170&message.id=173147&query.id=98620#M173147

Also look here.

http://sine.ni.com/nips/cds/view/p/lang/en/nid/201711

[Unitech Scales]

Dear sir

Thank you very much for your reply. I tried using Mb serial master query.vi and also read and write vi supparatly. But I am unable to read the registers. please help me.

regards

Prasanna Kumar N M

[Unitech Scales]

Dear sir

I am able to communicate with the instrument using "MB serial master query.VI" but, the instrument is sending data in 32 bit and I am unable to interprit the data read as this VI reads data only in 8 bit. Kindly help how to recieve 32 bit data. I tried changing the data indicator to 32 bit but it dint worked.  The instrument will send the data in floating point format of 4 bytes (32 bits)

Please help me.

Regards.

Prasanna Kumar N M

[unclebump]

Modbus protocol supports reading 16 bit register values. If you need floating point format, it has to be converted inside the labview code. you will need to read two 16 bit registers, then convert to floating point. You may need to swap the registers for HI/LO and maybe swap bytes in each register. I'm in the middle of our summer shutdown maintenance projects, so I can't figure out the conversion at them moment.

[unclebump]

try this page.

http://digital.ni.com/public.nsf/websearch/4EF459F549FCC7028625660A000A7629?opendocument&Submitted&&...

[Unitech Scales]

Dear sir

I am able to read all the register values in 16 bit.  Please help me how to convert this 16 bit arry into 32 bit flaoting number. The 16 byte grgister values are 4365(Hex) and C6B2(Hex) respectivly.  The 32 bit floating point decimal value will be around 230.0000.

Please help me.

Regards

Prasanna 

[unclebump]

Try this thread.

http://forums.ni.com/ni/board/message?board.id=170&message.id=195115

[Unitech Scales]

Dear sir

Thankyou verymuch for your kind help. I am able to gget the readings.

Regards

Prasanna Kumar N M