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Document the change in polarity of the uart(4) PPS capture.

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This commit is contained in:
Ian Lepore 2015-08-10 21:09:06 +00:00
parent fac6a198c3
commit e7dbaf581e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=286596
1 changed files with 14 additions and 0 deletions
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@ -31,6 +31,20 @@ NOTE TO PEOPLE WHO THINK THAT FreeBSD 11.x IS SLOW:
disable the most expensive debugging functionality run
"ln -s 'abort:false,junk:false' /etc/malloc.conf".)
20150810:
The polarity of Pulse Per Second (PPS) capture events with the
uart(4) driver has been corrected. Prior to this change the PPS
"assert" event corresponded to the trailing edge of a positive PPS
pulse and the "clear" event was the leading edge of the next pulse.
As the width of a PPS pulse in a typical GPS receiver is on the
order of 1 millisecond, most users will not notice any significant
difference with this change.
Anyone who has compensated for the historical polarity reversal by
configuring a negative offset equal to the pulse width will need to
remove that workaround.
20150809:
The default group assigned to /dev/dri entries has been changed
from 'wheel' to 'video' with the id of '44'. If you want to have