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

Henrik Maier hmnews at proconx.com
Thu Jul 17 02:31:14 CEST 2014

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.


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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