Hi,
 
the project looks good so far but I of course can't tell you whether your addresses/offsets are OK or not.
What you could try additionally: There are two options to swap address and data bytes in general settings. They perform a byte-swap of data and/or address. In principle the byte order is fixed and specified for MODBUS but it seems there are some devices out there that do not use correct order (at least that's my understanding why these options are there).
 
So simply try to set these options for address and/or data and check if it works.
 
If that does not help: trace your raw data stream and contact the vendor directly, may be they can tell you what's wrong in your set-up.
 
 
Gesendet: Montag, 20. Januar 2014 um 07:59 Uhr
Von: "Mr Lam" <lamtranhn@gmail.com>
An: openapc@lists.fedorahosted.org
Betreff: Re: Example of Modbus TCP Master
Hi,
I have been doing as your instructions but get no success. Please see the my attached project. In this project I have tested with both Unit ID of 0 and 1 but all LC_Numeric_Display fields still display results of 0 (it should display results greater than 0 as I viewed with other Modbus Tool).
Can you suggest some other hints on this matter ?
I am looking forwards to your assistance.
Thanks.
 
On Mon, Jan 13, 2014 at 1:37 PM, <qxc@gmx.de> wrote:
Hi,
 
please find attached a screenshot of the configuration that should fit to your problem. Regarding the IO base address offset I'm not quite sure, may be values have to be +-1 since I'm not sure if your PLC/the MOBUS plug-in starts counting at address 0 or 1
 
 
Gesendet: Samstag, 11. Januar 2014 um 12:35 Uhr
Von: "Mr Lam" <lamtranhn@gmail.com>
An: openapc@lists.fedorahosted.org
Betreff: Example of Modbus TCP Master
Hi there,
 
I recently downloaded OpenAPC for Windows x86 (my laptop's OS is Windows 7 Professional, 32bit) and I am getting familiar with Control Room's functions. I have been trying to get status of digital inputs and value of holding registers from a Siemens's PLC, which I programmed to work as a Modbus Server, and display the result to Control Room. But I could not succeed. I have been using some Modbus tool to check the performance of PLC and it is still working correctly (inputs and register of PLC give correct results to Modbus tool). 
So I would like to get help from experts of OpenAPC. Particularly I would like to have a simple example which can read status of Digital Input Register 1 and content of Holding Regster 40001 to Holding Register 40003.
 
Thanks in advance 
 
Regards 
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