Re: [ECOS] Timing differences before / after starting scheduler

[Sergei Gavrikov <sergei dot gavrikov at gmail dot com>]

On Sun, 22 Aug 2010, Tim Jaacks wrote:
> > Polling status/data from the FIFO generates quite a bit of traffic
> > on the chip's bus - I don't know how exactly the APB and AHB/APB
> > bridge work. I mean the speed you are demanding is maybe
> > too much for the worst case that can happen on the bus
> > (arbitrations etc). Add to that that you probably need
> > an interrupt to tell you there is first data, interrupt latency
> > and driver reaction time - maybe this is too much for a real
> > application.
> >
> > I think for this case the DMA is surely a better idea.
> >
> > See also http://permalink.gmane.org/gmane.comp.hardware.arm.lpc2100/49688 -
> > someone had problems even using the DMA ...
> >
> > Why this runs more 3 times slower if there is nothing but
> > this thread running with disabled interrupts, I have no idea...
> Thanks very much for the link, that was very interesting to read!
> Seems as if using DMA is the only practical way to get the interface running 
> at that high speed.
>
> Anyway, I still find it confusing that the actions take more time when the 
> scheduler is started. If anyone has an idea, why this might be the case, 
> please reply on this thread. I will be very thankful.

Hi

Silent guess. May be that is idle's thread "job" on lpc targets. By default
cdl_option CYGHWR_HAL_ARM_LPC24XX_IDLE_PWRSAVE is *ON* and that stops the
processor clock in the idle loop, try to turn the option OFF and rebuild
eCos, though I'm not sure that can help with the issue.

Sergei

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