Re: [RTnet-developers] Ethernet IP

[Jan K. <jan...@we...>]

Am 28.09.2010 23:17, Glen Wernersbach wrote:
> Jan,
> 
> My basic concern was to keep the data flowing from the NIC to my program as
> close to hard real time as possible. I know doing Linux calls can break hard
> real time especially when I want to receive a UDP packet every 1ms.

Is that UDP packet part of your control loop? Why do you need the whole
opener stack then? Or is there more?

> 
> The only thing Ethernet IP really gives you real time is optional support
> for the Ethernet 1588 timing standard so you know what the jitter was in
> receiving the packet over the Ethernet line. The 1588 support is not yet
> implemented in opener. The rest is just a protocol for handling critical
> data over TCP and UDP. Unfortunately, I have a device that needs to work on
> Allen Bradley controllers which only support this real time protocol.
> 
> All I want to do is replace the Linux calls in networkhandler.c
> (socket,bind,listen...) with RTAI real time calls.

Additionally, you will have to configure the socket resources, namely
how many buffers each socket should pre-allocate for its real-time
operation (that's the major difference to normal networking stack that
do on-demand allocations). See the examples.

Jan