Re: rt application question with rs232 communication

[Leon Woestenberg <leon.woestenberg@gmail.com>]

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.

That's on XScale IXP4xx @533 MHz,

Regards,
-- 
Leon
--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html