Date: Tue, 29 Apr 1997 13:22:39 +0930 (CST) From: Michael Smith <msmith@atrad.adelaide.edu.au> To: nbc@vulture.dmem.strath.ac.uk Cc: freebsd-hackers@freebsd.org, nbc@neophyte.dweeb.net Subject: Re: FreeBSD As Motor Controller? Message-ID: <199704290352.NAA19419@genesis.atrad.adelaide.edu.au> In-Reply-To: <199704290032.BAA00916@neophyte.dweeb.net> from "nbc@vulture.dmem.strath.ac.uk" at "Apr 29, 97 01:32:53 am"
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nbc@vulture.dmem.strath.ac.uk stands accused of saying: > > I am currently in the process of implementing an embedded motor control > system using a well know real-time UNIX, which has turned out to > be slightly overkill. The system is soft real-time, which made > me wonder if FreeBSD would be up to the job - I envisage a stripped > down system, running on PC/104 hardware (already tested with F/BSD), > the drivers residing at device level, preferably in LKM format. This is certainly viable. If you want to get really carried away, you could throw your final filesystem onto a PC-104 flash card too. > At the moment we are using stepper motors, although this may change > in the future, driven by pulses generated from an I/O board on the > ISA bus. My major concern with FreeBSD is interrupt latency, which > is excellent with the current system. Given that we are using 100MHz > Cyrix 586 CPUs, I'd appreciate it if anyone could give me a ballpark > figure on the latency, and indeed the typical variations in such one > would expect from a lightly loaded system, or perhaps some way to > determine this for myself. Bruce Evans would be _the_ person to talk to about this; if he doesn't respond to your posting (likely he will), he can be contacted as bde@freebsd.org. If you have access to external timing hardware, write an interrupt handler that responds by fiddling an output bit, then use the hardware to measure the interval between the interrupt being generated and handled. Any halfway decent counter will do this; most have min/max/mean modes that should give you a good feel for 'real' interrupt response time. > Neil Clark -- ]] Mike Smith, Software Engineer msmith@gsoft.com.au [[ ]] Genesis Software genesis@gsoft.com.au [[ ]] High-speed data acquisition and (GSM mobile) 0411-222-496 [[ ]] realtime instrument control. (ph) +61-8-8267-3493 [[ ]] Unix hardware collector. "Where are your PEZ?" The Tick [[
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