Jim,
I am using Windows 7. 
I didn't see to be a problem with the address bytes -
but that doesn't mean there isn't one.
BTW, simply by using a divide by 256 I can get good
data for register values up to 255.  :-)
Your efforts are appreciated, especially considering
the complexity of the "free" software.
Again, thanks!
Albert

From: Jim Hart <openapc@gmail.com>
To: openapc@lists.fedorahosted.org
Sent: Sunday, January 13, 2013 3:58 AM
Subject: Re: Modbus

Albert,

it seems like there is a problem with the byte order swapping, in your
case probably only the data bytes but not the address bytes have to be
swapped. We'll prepare a new version for you for testing and send it
to your personal mail address directly.

Which operating system are you using exactly?

Kind regards

Jim



On 12/01/2013, Albert Serrero <ajs_tech@yahoo.com> wrote:
> Here's my situation.
>
> I am reading a 16 bit integer holding register on my serial modbus RTU (by
> the way, it works fine with Mango).
>
> On OpenAPC, a value of 0 reads 0.  That's ok.
> A value of 1 at the controller reads 256 on OpenAPC (2 => 512, 3 => 768, 4
> => 1024, etc.)
>
> The obvious logical assumption is that the byte order is reversed.
>
> But when I UNCHECK the invert byte order on the MODBUS definition under the
> "Basic" tab (originally checked), I always read a value of  65521 or xFFF1
> on all the mapped registers regardless of their value.  There's no question
> that there's a problem here.
>
> I have no idea how to modify the source code / recompile - just thought that
> you'd guys would like to know that the "Invert byte order" option does not
> work (unchecked mode) - seems like a simple to fix to make a simple modbus
> RTU functional.
>
> Thanks again.
>
>
>
> ________________________________
>
> From: Jim Hart <openapc@gmail.com>
> To: openapc@lists.fedorahosted.org
> Sent: Thursday, January 10, 2013 5:23 AM
> Subject: Re: Modbus
>
> Albert,
>
> thank you for your interest in our products.
>
> The MODBUS plug-ins already support 16 bit integer values. The width
> of them depends - conform to the MODBUS specification - on the chosen
> IO mode. This mode influences if the data are 8 bit int, 16 bit int or
> 32 bit float.
>
> In case you need something additional that is outside of the scope of
> the MODBUS specification you can add this easily, the sources are open
> and available at
> https://fedorahosted.org/OpenAPC/browser/plugins/libio_modbus_rtu_master
>
> Alternatively you can let us do this modification as soon as we have
> some time for it. In this case we'd need detailed information which IO
> mode you're using, how many bytes have to be concatenated and which
> byte order they have.
>
> Kind regards
>
> Jim
>
>
>
> On 09/01/2013, Albert Serrero <ajs_tech@yahoo.com> wrote:
>> Hi, I just set up OpenAPC and was running a test project with some
>> success.
>> I have a low cost modbus controller connected to my Windows 7 PC via
>> serial
>> USB.  Most software platforms that support modbus allow some modification
>> of
>> the type of data that is expected back from the modbus device:  floating
>> point vs 16 bit integer at a minimum.  My device only supports 16 bit
>> integer as many low cost modbus devices do.
>>
>> Is there a way to specify or adjust for this with the Modbus control?
>>
>> Thanks in advance.
>> ajs
>
>
> --
> Kind regards
>
> Jim Hart
>
> http://www.lasermarkingsoftware.com
> http://www.openapc.com
>
> Follow us at Twitter: https://twitter.com/#!/openapc
> _______________________________________________
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--
Kind regards

Jim Hart

http://www.lasermarkingsoftware.com/
http://www.openapc.com/

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