Modbus frame

[K C]

I am still confused, are you talking about sending to the micro or writing to a file ? 

[azwhoony]

I no longer have the problem with any device that I use right now. From front panel,it will show the value as expected but after write to txt file. the txt file itself doesn't show like the string at front panel. We're discuss on 0x20 value I'm getting after run your program isn't it? This is what I'm trying to tell you. The problem isn't part of the device at all. Can you just try run this code at send back to me the txt file. Just send any modbus frame at Cheat Modbus String. Do you see any changes at the txt file if u send any 0x00? 

[K C]

Here it is. No problem no other data in the file then I would expect.

Curious what you see in the txt file.

Message Edited by K C on 11-14-2007 09:44 AM

[azwhoony]

Hi .

I finally know what's going on. The .txt file will show 0x00 if only I open the file back using labview. If I just copy the character string in test.txt file into string indicator and display it in hex, it will show 0x20. I wonder if we save this kind of character in database, and then using another program to open it (not labview), what will happen...

Anyway..I will do some more reading and test for any application using labview. Thanks for wasting your time on me KC.   

Thanks a lot

[K C]

and if you open the file with a better editor like UltraEdit you can see the binary data without any conversion.

No time wasted (I think    ) glad that it's solved

Message Edited by K C on 11-14-2007 11:17 AM

[gdah]

hi...i have some problem when write multiple data to my device. If i want to write single register i will send 13 byte including slave add, function code and CRC for example 0210000600020443480000D059. I'm not sure either the query string that I send in multiple way is correct or not for example 021000060002044348000040400000D059. Is it because of the query string is incorrect so that my device cannot write the data? please view the attachments file for more details. The attachment files shows the error, query string and modbus receive frame.  thanks..

[K C]

Hi,

Next time please start a new thread for a new question.

The first string has the correct length but I get a different CRC. It is also impossible that the two examples you give have the same CRC

This is the string:

02 10 0006 0002 04 4348 0000 E9 53

02        Slave address

10        Force Multiple Registers

0006    Start register

0002    Number of registers

04        Number of transmitted data bytes

4348    data for first specified register

0000    data for second specified register

E953   CRC

Does this help ?

[gdah]

hi..i already open new topic but no one view my question.heheh...sorry for the typing error.actually i get different CRC when i send single or multiple data .. my concern is more on query string that i send and i'm using modbus library to write multiple data. if  u see in my attachment file the data are send in an array..my problem is i not sure either the query string that i send is correct or not..because if i send more that 13byte , time out error will occured.any idea??

u can reply to this add

http://forums.ni.com/ni/board/message?board.id=250&message.id=34993&query.id=83281#M34993  

[K C]

I saw this question but there was not enough data to understand your question.

I don't use the ModBus lib. so I can't help you with this.

Did you already tried to increase the timeout ?