Re: modbus over tcp/ip

[John Dobbins <jad@lepp.cornell.edu>]

Paul,

I looked at the available modbus code a few months ago and found it 
supported only a small subset of modbus codes. It seems it was developed 
for talking to a particular PLC, via register reads and writes, rather 
than a more general modbus device. If your goal is similar you may be 
happy with the CLS/BNLS code. If your goal is to be able to support a 
variety of modbus devices you'll need to do some additional 
device/driver development.

Sheng,

I am also interested in learning about the modbus device support at SNS.

John Dobbins
Research Support Specialist
Laboratory for Elementary Particle Physics
Cornell University


Paul Sichta wrote:
> Sheng,
> I visited SNS a few weeks ago and Ernest showed me the Beckhoff hardware 
> which he said you wrote a modbus driver/device support for. Was that 
> working well? I am thinking of trying out the Beckhoff stuff.
>
> I will be supporting some modbus tcp/ip devices in the near future and 
> have the CLS and some upgraded (APS?) source but haven't looked at it 
> yet. What limitation did that have for you, so that you needed to write 
> a new version?
>
> Regards,