Re: [Xenomai-help] Gumstix arm pxa

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

Stefan Schaal wrote:
> Hi Gilles,
> 
>    if aperiodic has better accuracy, what is the minimal time  
> resolution one can obtain, e.g., on a x86 (I assume that asking for  
> too short a wait can lead to system freezes)? Coming from the vxWorks  

The sleep time resolution is bound to the frequency of the hardware
timer used. I do not know x86 details that much, but I seem to remember
that the 8254 timer, the worst one, has a frequency around 1 MHz, which
gives you a resolution of 1us, enough for most uses I believe.

> philosophy, we have been running a 100000ns periodic clock (x86) to  
> work with semaphores and timing statements. Seemingly, you recommend  
> not to use the periodic clock. The rt_timer_ns2ticks and  
> rt_timer_ticks2ns seem to return 0 if the aperiodic clock is used. Is  
> this reasonable, or should they return that ticks and nanoseconds have  
> the same value in this case?
> 
>    Sorry, I am just learning about this different way of using a ROS.

either your system is misconfigured (if you have a periodic timer, any
time duration smaller than the timer period will give you a duration of
0 ticks, results are rounded toward 0), or there is a bug somewhere.

cat /proc/xenomai/timebases will tell you.

What xenomai version are you using exactly ?

-- 
					    Gilles.