From owner-freebsd-hackers Sun Sep 30 11:48:57 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from mail.shell-server.com (24-109-11-245.ivideon.com [24.109.11.245]) by hub.freebsd.org (Postfix) with SMTP id 7FF9337B415 for ; Sun, 30 Sep 2001 11:48:49 -0700 (PDT) Received: (qmail 13687 invoked from network); 30 Sep 2001 18:22:06 -0000 Received: from betsy.shell-server.com (HELO there) (192.168.3.2) by erin-rl0.shell-server.com with SMTP; 30 Sep 2001 18:22:06 -0000 Content-Type: text/plain; charset="iso-8859-1" From: Bart Kus Message-Id: <200109301318.44290@EO> To: gkshenaut@ucdavis.edu, Greg Shenaut , hackers@FreeBSD.ORG Subject: Re: precise timing Date: Sun, 30 Sep 2001 13:23:08 -0500 X-Mailer: KMail [version 1.3] References: <200109301747.f8UHlsA35003@thistle.bogs.org> In-Reply-To: <200109301747.f8UHlsA35003@thistle.bogs.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sunday 30 September 2001 12:47, Greg Shenaut wrote: > Well, setitimer has a maximum rate of 100 Hz, with a slop factor > sometimes much greater than 10 ms. This was the result of some > recent testing on a lightly-loaded standard 4.3 system. That's not good enough. :/ > How many stepper motors are you driving? If it's only one at a time, then > maybe the speaker port on the motherboard (a programmable counter-timer) > would be more reliable. I like the speaker port idea. Can one program the speaker port to generate an int/signal/un-block using bsd's kernel API? > Another idea is to use a fifo'ed UART's data out > line and fiddle with the baud rate to vary the speed of the pulses. I don't think this will provide the "smoothness" I want. Going from 2400->4800 steps/sec for example would be a huge jerk. Need SMOOTH transition (constant-acceleration). But the speaker port idea sounds great. --Bart To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message