Labview: TCp Open Issue!

[Bk576]

Hi Everyone,

    I'm working on a MODBUS routine for communication with one of our control modules. I'm using NI's Modbus library to initiate a connection, check the registers, etc then report the results back to a teststand seq for fruther analysis.

    Problem? I made a few minor adjustments to the library (just the main routine) because i only need to read the registers for now. However, when I conenct with the TCP Open Connection, nothing happens. Well, not completely true.. I sinffed the connection with Ethereal and I get the following errors...

**************************************************************

1)

SENDING:

TCP: Src Port 2061, Dst Port: 502, Seq: 13, Ack: 10 , Len:12

Checksum: 02x282d [incorrect, should be 0xfd6b]

2)

RECEIVING:

Modbus/TCP:

-Modbus: Function 4: Read input registers. Exception: Illegal data address

exception code: Illegal data address (2).

***************************************************************************

I understand the second one and believe it's related to the first but ....?

Does anyone have any ideas or suggestions? I'd go into the TCP OPEN.vi if I could, but it wont let me, so...?

Thanks Again,

BK

[Matt_S.]

Hi BK576,

Does this still give you problems if you don't make your modifications to the MODBUS libraries? What changes were made? Could you possibly submit an NI-Spy capture taken while seeing this error?

Regards,
Matt S.

[Bk576]

Hi Matt,

    Thanks for the reply! I actually figured it out, and now it works great!

Thanks Again,

BK

[Matt_S.]

Great to hear it BK!

Let us know if there is any other way we can help!

-Matt S.

[Chei]

BK,

What was the problem and solution with your invalid checksum I am also seeing the same problem.

James