Re: rt application question with rs232 communication

[Cliff Brake <cliff.brake@gmail.com>]

On Sat, Mar 14, 2009 at 10:07 PM, Leon Woestenberg
<leon.woestenberg@gmail.com> wrote:
> Hello Cliff,
>
> On Tue, Mar 10, 2009 at 1:44 PM, Cliff Brake <cliff.brake@gmail.com> wrote:
>> Clarification, I don't have the RT patch applied, just CONFIG_PREEMPT
>> from Linus's kernel.  Reviewing my notes from several years ago, I ran
>> into a similar issue and the RT patch fixed it, so now to figure out
>> the best way to get a recent RT patched ARM kernel ...
>>
>>> timing.  However, it seems that the system has trouble receiving the
>>> response in a timely fashion.  I often observe that it takes at least
>>> 10ms for the application to receive the response data after the data
>>> has appeared on the rs232 bus.  Is the RT patch something that would
>
> We are running a real-time RS-485 protocol where the time window is 1
> ms and only under heavy load we got deadline misses > 1 ms.
> Unfortunately I didn't measure the max latency then, but 10 ms sounds
> like excessive latency to me.
>
> Under 2.6.24.7-rt24 (or whatever -rtxy in that series) we have never
> missed the 1 ms deadline.

Thanks Leon.  I guess its pretty obvious at this point I need the RT
patch.  Still trying to figure out the best way to get this with
2.6.27 or later -- I really don't want to go back to 2.6.26.

Thanks,
Cliff

-- 
=======================
Cliff Brake
http://bec-systems.com
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