"Estabridis, Janet P" <[EMAIL PROTECTED]> writes:
> What do you mean by time critical ? Is your network localized? What I'm
> getting at is this -- depending on what your data rates are and how your
> data communication is set up you may have no problems using the non-realtime
> networking.
>
> My personal expericence is that We have 8 embedded CPUs with 100BaseTX
> ethernet and 5 other computers needing data from the 8 embedded CPUs. And
> the 100BaseTX is fine, a human can't tell the difference. For the small
> amount of really time critical data (6 bytes from each of the 8 embedded
> CPUs every 30 Hz), I'm setting up an RS485 net and scheme.
Could you please tell if there are tricks to this? Namely, I have two
rate-monotonic tasks, 500ms and 50ms periods. They read data from the
shared memory; these data are, in turn, written to the shared memory
by a Linux process that receives them from the network (100Mbps
ethernet). I have noticed that the 50ms-task causes problems, i.e., it
is likely that the NIC buffer gets full (or something similar), which
then causes problems at the sender (on another machine in the
LAN). The sender should send data at the rate of about 250kBps, but it
takes about 1.5 seconds to send one big (225kB) message when the
50ms-task is running at the receiver node. With just the 500ms-task,
the sender does not get delayed.
Thanks,
Aleks
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