Date: Sun, 30 Sep 2001 13:23:08 -0500 From: Bart Kus <bsd@shell-server.com> To: gkshenaut@ucdavis.edu, Greg Shenaut <greg@bogslab.ucdavis.edu>, hackers@FreeBSD.ORG Subject: Re: precise timing Message-ID: <200109301318.44290@EO> In-Reply-To: <200109301747.f8UHlsA35003@thistle.bogs.org> References: <200109301747.f8UHlsA35003@thistle.bogs.org>
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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
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