[Xenomai-help] Two real time NICs in same PC? (RTnet)

[Xenomai-help] Two real time NICs in same PC? (RTnet)

[Benjamin Biegel]

I have only found documentation about the possibility to run a 
non-RT-NIC and a RT-NIC at the same time, which is possible.

But is it possible on the same PC to have:
- One NIC being master or slave in an RTnet network
- One other NIC capturing frames with RTcap
?

(The whole point is to have a network of PCs running RTnet, so that 
their clocks are synchronized. Then have these same PCs capture frames 
via RTcap. In this way the captured timestamps can be compared and  
Ethernet  frame travel times can be calculated.)

Thanks :)

Benjamin

Re: [Xenomai-help] Two real time NICs in same PC? (RTnet)

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 901 bytes --]

Benjamin Biegel wrote:
> I have only found documentation about the possibility to run a 
> non-RT-NIC and a RT-NIC at the same time, which is possible.
> 
> But is it possible on the same PC to have:
> - One NIC being master or slave in an RTnet network
> - One other NIC capturing frames with RTcap
> ?

Yes, this is possible. It is even the default if you use RTnet's startup
script and config (only one NIC is configured, and if there are two NICs
of the same type, only the first one is claimed by RTnet).

> 
> (The whole point is to have a network of PCs running RTnet, so that 
> their clocks are synchronized. Then have these same PCs capture frames 
> via RTcap. In this way the captured timestamps can be compared and  
> Ethernet  frame travel times can be calculated.)

Note that the measurement jitter /may/ still be in the same order of
your travel delays.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 257 bytes --]

Re: [Xenomai-help] Two real time NICs in same PC? (RTnet)

[Benjamin Biegel]

[-- Attachment #1: Type: text/html, Size: 1869 bytes --]

Re: [Xenomai-help] Two real time NICs in same PC? (RTnet)

[Jan Kiszka]

[-- Attachment #1: Type: text/plain, Size: 557 bytes --]

Benjamin Biegel wrote:
> Thanks!
> 
> I can see in the source that the capture stamping uses the rtdm_clock_read().
> 
> When several PCs are on the same RTnet, they get synchronized due to the TDMA. 
> But what clock is it that is synchronized on the PCs? How do I read and use this 
> clock? What file can i see this in?

Check examples/xenomai/native/tdma-api.c.

> 
> Would it be possible to stamp received frames through this synchronized clock 
> instead of the system clock?

No, but you could do the calculation afterwards.

Jan


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 257 bytes --]