> -----Original Message-----
> From: gheroghe vintila [mailto:community-noreply@qnx.com]
> Sent: March 27, 2010 5:49 AM
> To: qnx4-community
> Subject: Real Time gpio task
> 
> Hy, i am trying to create a 250 microsecond task, just toggleing a
> gpio pin from a port with out32 instructions.
> The problem is with jitter, when I measure the jitter even a a
> 1milisecond impulse signal, its huge (average 500 micro-seconds and the
> max is sometimes larger than the signal itself). i must be doing
> something wrong.

> I set the clock period to 1 milisecond, set the priority to about 60
> (larger than all of the user processes), but still the jitter is big,
> to big for a real time application, remember a want a 250 microsecond
> task. I even tried setting up a timer with a repetition interval of 250
> microseconds using the same pretext as above but i had no good
> results.(same jitter)

Timer resolution will be that of a clock period. If you want a 250 us timer you need to set the timer resolution to 
250us.

That being said 250us will results in 4000 interrupt seconds.

> I would also like to add that i am using a AT91SAM9260-ek board for my
> target, and i`m using qnx neutrino 4.
> How can i lower that jitter to a normal level, is there some kind of
> way to make a real-time below or even 1 milisecond without jitter?
> 
> 
> 
> _______________________________________________
> 
> QNX4 Community Support
> http://community.qnx.com/sf/go/post50618
>