From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4E402433.4090103@domain.hid> Date: Mon, 08 Aug 2011 20:00:19 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <1312821858.88556.YahooMailClassic@domain.hid> In-Reply-To: <1312821858.88556.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 08/08/2011 06:44 PM, Philip Ha wrote: >> 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. > > Hi Gilles, > > I am not sending characters, I am sending a pulse from a > function generator into the DSR pin and looking for the rising > edge event ( RTSER_EVENT_MODEMHI ). Any latency in the system > should be similar for every pulse it receives, therefore the > time between pulses should still be 1000000us. The question remains: are you sure the UART does not introduce the delay, have you checked the datasheet? -- Gilles.