From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4E3BE7B7.3040505@domain.hid> Date: Fri, 05 Aug 2011 14:53:11 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <1312486056.62780.YahooMailClassic@domain.hid> In-Reply-To: <1312486056.62780.YahooMailClassic@domain.hid> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] clock problem List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philip Ha Cc: Xenomai-help@domain.hid On 08/04/2011 09:27 PM, Philip Ha wrote: >> Would it be possible for you to send mails formatted correctly? >> >> Then the bug is somewhere in between the serial line and the test >> application, including possibly in the driver. >> >> In order to know where it is, you should compute the latency at each >> point on this path: when receiving the interrupt, when waking up the >> task, etc... > > Hi Gilles, > > Sorry for the formatting, I am new to mailing lists. > > I have looked at the latency in the 16550A driver. The first thing > the driver does in its ISR is to call rtdm_clock_read and store the > resulting timestamp in a "struct rtser_event". The code I posted > grabs this structure. If I use this as my timestamp I get the exact > same timing results. are you sure that the interrupt triggers as soon as you receive a character, and not upon timeout when not receiving characters for some time? After all, 100us is approximately the time to transmit one character at 115200 bauds on the serial line. -- Gilles.