[En-Nut-Discussion] Industrial interfaces (Modbus TCP, Profinet, etc.)

Philipp Burch phip at hb9etc.ch
Thu Jul 17 20:03:26 CEST 2014

Hi Henrik!

Thanks for your explanations. I guess I'll then stick to Modbus TCP as I
don't expect anyone to be happy if I tell them about the license fees
when there's a free and even easier alternative ;)
Terminating the connection in response to an error condition sounds
reasonable, I guess that will work.

Best regards,

On 17.07.2014 02:31, Henrik Maier wrote:
> Hi Phillip,
> We have implemented several commercial products using Modbus/TCP
> based on Nut/OS and this is straight forward to implement by
> following the official specs which are open and available.
> Regards your fragmentation concern, the Modbus/TCP packet size is
> below the minimum fragment size, so the protocol relies on a single
> message not to be fragmented.
> But you have to allow for multiple messages in one TCP segment,
> that's what the MBAP header is for so you can check how many bytes to
> read from the read queue.
> In case something goes out of synch or bogus, the spec mandates
> closing the connection and a new one to be established to get a clean
> start.

> ProfiNet is not as easy as Modbus as it is not really open.
> You can implement conformance Class A and B devices using standard
> Ethernet hardware. But Class C requires a special ASIC as the
> isochronous real-time requirements of Class C cannot be met with
> ordinary TCP/IP and Ethernet.
> But the biggest impediment is not of technical nature but
> commercial.
> In order to participate in the ProfiNet world you need unique vendor
> IDs and Indent numbers. In order to get those IDs registered, you
> have to get your device conformance tested (this is mandatory for
> ProfiNet) which is expensive and it is probably not commercially
> viable trying to achieve conformance with a homebrew stack. You would
> be better off licensing a commercial stack which is known to pass
> conformance test.
> There are also various trademark licensing rules requiring you to
> become a paying member of the Profinet organisation in order to use
> the ProfiNet trademark in conjunction with your product.

> Henrik
> On 17/07/2014 4:31 AM, Philipp Burch wrote:
>> Hi everyone,
>> I'd like to ask if anyone of you has experience with integrating 
>> Ethernut-driven devices in industrial networks based on Ethernet. 
>> Sometime in the near future, we will need to implement some
>> standardized industrial interface in one of our devices, such as
>> Modbus TCP or Profinet. Does someone already have such code at hand
>> by chance? I'm not concerned about Modbus TCP, this should be
>> fairly simple to implement. But as far as I understand Profinet,
>> this works below the transport layer, i.e. it does not (only) use
>> TCP or UDP, but something different. Or are there other popular
>> interfaces that could be a good choice? We do have an FPGA on that
>> device, but I'd prefer to do the network stuff only in the
>> microcontroller, so EtherCAT is not really an option.
>> Thank you!
>> Best regards, Philipp 
>> _______________________________________________ 
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