From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 3204 invoked by alias); 14 Oct 2003 17:25:58 -0000 Mailing-List: contact ecos-discuss-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: ecos-discuss-owner@sources.redhat.com Received: (qmail 3197 invoked from network); 14 Oct 2003 17:25:56 -0000 Received: from unknown (HELO mop.awox.com) (195.6.124.91) by sources.redhat.com with SMTP; 14 Oct 2003 17:25:56 -0000 Content-Class: urn:content-classes:message Date: Tue, 14 Oct 2003 17:25:00 -0000 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Message-ID: X-MS-Has-Attach: X-MimeOLE: Produced By Microsoft Exchange V6.0.4417.0 X-MS-TNEF-Correlator: From: "Vincent Leclaire" To: Subject: RE: [ECOS] Maximum sampling rate X-SW-Source: 2003-10/txt/msg00231.txt.bz2 Hi Gary, I'm afraid I agree with you... I did not even thought about doing it "by hand" since I will anyway have to reproduce it and have to be quite independant of the processor clock (several-target-system!). My original idea was to use an high-speed timer that would trigger interrupts, with all the overhead involved, etc. It is theoretically possible for sure but I am looking for real-world information... even if I'm afraid I know the answer :-) (just a precision - this operation will only have to take place from time to time and will not last for long, so the issue is really about feasability: it is acceptable to have only this running when it happens !) Thanks VL -----Original Message----- From: Gary Thomas [mailto:gary@mlbassoc.com] Sent: Tuesday, October 14, 2003 7:19 PM To: Vincent Leclaire Cc: ecos-discuss@sources.redhat.com Subject: Re: [ECOS] Maximum sampling rate On Tue, 2003-10-14 at 11:07, Vincent Leclaire wrote: > Hi folks, >=20 > I have to design an application that will sample a given pin in order to > "reproduce" the recorded sequence. The signal might go up to 500KHz > (sampling at 1MHz+), target is ARM7 100MHz clock (or more). >=20 > >From your experience, does this seem feasible safely ? What's the best > way to proceed (I will probably have to use some sort of interrupt/timer > so I'm talking about eCos relationship with interrupt handlers and the > like) ? >=20 Is this some automatic sampling (i.e. triggered by an external clock or timer), or must you do it "by hand?"=20=20 If you have to do it manually, at these data rates, your processor=20 won't be able to do much of anything except grab samples (one every=20 2us). I doubt that you could even write code which performs this reliably: while (need_sample) { while (!sample_time) ; collect_sample() } You might be able to use some sort of high speed timer to determine "sample_time", but my guess is that you couldn't ask that question, collect and store a piece of data and get around the loop again fast enough (2us) to keep up. --=20 Gary Thomas MLB Associates -- Before posting, please read the FAQ: http://sources.redhat.com/fom/ecos and search the list archive: http://sources.redhat.com/ml/ecos-discuss