Am 22.08.2005 um 17:26 schrieb Søren Schmidt:
On 22/08/2005, at 10:08, [EMAIL PROTECTED] wrote:
what would be the best approach to implement aps on FreeBSD?
I got an Accelerometer driver which will deliver data. First
Version is available at
https://sourceforge.net/project/showfiles.php?
group_id=138242&package_id=160977
We have to poll the device for information quiet often to detect a
possible shock early enough to park disk drive heads.
Urhm, what type of "accidents" is it we want to protect against here ?
It will take several tens of mS to get the heads parked if not
hundreds, and the worst case scenario would be that the "accident"
will happen just as the heads are on the way to the parking zone
which would *really* destroy data on there, unless the disk has
special HW to just quickly lift the heads or something.
I have no insight into either IBM's or Apple's implementation, but
I've read that they both rely on detecting the machine being in
freefall, or similar acceleration states, as a cue to have the HD
park the heads before a possible impact.
Early reports from Mac enthusiast sites (and I believe similar
reports from IBM users) indicate that the hysteresis is so small that
gently pounding the table the notebook is sitting on will make the
drive park the heads, and lead to 10 to 20 seconds delay before the
drive can be accessed again.
Given how tightly coupled mechanically the HD in most notebooks is to
it's shell, it seems a very good idea to pursue.
If you have access to a new(ish) PowerBook, I recommend checking out
http://www.kernelthread.com/software/ams/. The sensitivity of the
accelerometer is truely astounding. (For those who haven't seen it:
you turn the notebook, and the demo window is turned so it stays
level. It takes *really* small movements to confuse the system.)
Stefan
--
Stefan Bethke <[EMAIL PROTECTED]> Fon +49 170 346 0140
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