[etherlab-users] Arrival of large amounts of data

[Andreas Stewering-Bone]

Hello,

it depends on your system bandwidth.

What is your cycletime?
Do you need all frames with the same cycle time?
The master splits the data automatically or via predefined domains in 
several frames?
The master use the diffent buffers of the network card automatically.

But note, to have a good multiframe configuartion you should use a real 
stupid card (Realtek) not the Intel stuff.

You have the possibility to use more than 1 master to reduce your 
bandwidth load for the network card.

Also you have to check the bandwidth of the PCI bus for this 
configuration, PCI Express is much better.

I think you are using oversampling slaves, or?

The master does not poll. You have to to prepare a setup like
-wakeup
- process frames (X times)
- calculate
- write frames (X times)
-sleep!!!!!

- You have to compare your frame cycle time, given by the physics and 
number of frames, your calculation time and your process cycletime. The 
cyletime should be minmal 2 times greater than the sum of the other times.

Best regards


Andreas




Am 20.10.2011 18:24, schrieb Shahbaz Yousefi:
> Hi,
>
> Me again, but on a totally different subject.
>
> If you remember, on one of the early emails you said:
>
> > *ecrt_master_receive(master_ptr): Fetches ethernet (yes etherNET!) 
> data from the card.* This ethernet packet contains all your input domains.
>
> Let's say I have 150 slaves, which with the current configuration, 
> require the EtherCAT frame to be split in 50 Ethernet frames. Now we 
> checked with some data sheets and we saw that our network card has a 
> buffer that can hold 64 Ethernet frames.
>
> My question is, what happens if we double the size of our network? If 
> use 300 slaves (that would produce 100 Ethernet frames on each 
> master_send), wouldn't that overflow the network card's buffer and the 
> data lost?
>
> Or, when the kernel module ec_master is loaded, does that poll the 
> network card and store the frames in memory? In that case, 
> ecrt_master_receive would be reading frames from _that_ memory instead 
> of the card itself.
>
> Shahbaz
>
>
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>    


Mit freundlichem Gruß

Andreas Stewering-Bone

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