On Sunday 30 September 2001 12:30, Bakul Shah wrote:
> Are you controlling the rotation speed of the drill or the
> x,y,z position? I'd guess the latter. Don't you also need
I am controlling XYZ.
> guaranteed real time response (which FreeBSD won't provide
> you)? I suppose if you are controlling the position (and not
> the velocity) RT response won't be too critical. At any rate
Hrm, I was planning on investigating the RT capabilities of fbsd after I got
myself a decent timer mechanism. I was hoping they would be enough to get
close to RT. I have an SMP system I can use, so 1 CPU can be dedicated to
the task.
> you are better off writing a device driver which can run
> timing critical code while blocking out all other interrupts.
Not an option. It would stall the whole system during the (possibly 20
minute) drilling operation. Maybe it'll be possible with SMPng, but not now.
> Or else between the time you measure time and supply the next
> pulse a higher prio interrupt handler else may sneak in. As
I'm hoping higher-priority interrupts will be quick about their work. A few
microseconds or 10s or possibly 100s hopefully won't upset the drill too much.
> was suggested you may want to consider a dedicated cpu based
> controller. Thre are a number of solutions for hobbyists
> (such as the handyboard, see www.handyboard.com).
Unfortunately, money is a big factor. So that's not an option. :/
> Is this a totally homebrew drill or something from a kit?
> I'd be interested in details (probably better offline since
> the interection of freebsd s/w hackers & h/w hackers is
> tiny).
It's home brew, I'll forward you more details in personal email.
--Bart
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