From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <43B42977.6050404@domain.hid> Date: Thu, 29 Dec 2005 19:22:47 +0100 From: Hannes Mayer MIME-Version: 1.0 Subject: Re: [Xenomai-core] 2.4.32 compilation error + old timer example problem References: <43B1F5CE.7030407@domain.hid> <43B27936.2000108@domain.hid> <43B303A8.7010903@domain.hid> <43B30DB0.3080104@domain.hid> <43B30F30.9000603@domain.hid> <43B31E6C.9040906@domain.hid> <43B3C5D9.50802@domain.hid> In-Reply-To: <43B3C5D9.50802@domain.hid> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: xenomai@xenomai.org Philippe Gerum wrote: [...] >> Just one question: what's the reason why the periodic mode >> is disabled by default ? >> > > Because AFAICT, most people would rather use the aperiodic timing mode > in usual configurations for a much better accuracy. Since the periodic > mode uses the available hw PIT and programs it once (or even some > decrementer but without handling the time drift when reprogramming it > after each shot), it suffers from cumulated rounding errors of the > period. If you look at the jitter results of a trivial periodic loop > over a broad timescale, you will see the wakeup time irremediably drift, > whilst the average interval between shots remains stable and reasonably > accurate. The periodic timer should be used for configurations that only > need to enforce delays or timeouts, and not, well, precise timings. Thanks Philippe! If it's for accuracy, keep it that way! Best regards, Hannes.