David,
running RPi with GPS+PPS here.
I compiled my own kernel and the one major gotcha I had was an RTFM
issue. The kernel used on the RPi is not the compressed vmlinuz
kernel used on PC's. I recompiled my kernel 10 times or more before I
went back scouring the 'net to find out the kernel in use was the
kernel.img file. Reason I say this is the first time I thought I had
this working I was seeing kernel generated PPS signals and not GPS
generated PPS signals. Life got much easier when I figured that out
:)
Having said all that this is what I see in my syslog when my system
restarts, my GPS has battery backup so it's not a cold start on it
when I reboot my RPi.
Nov 15 19:17:41 pisces kernel: [ 102.192261] pps_core: LinuxPPS API
ver. 1 registered
Nov 15 19:17:41 pisces kernel: [ 102.192269] pps_core: Software ver.
5.3.6 - Copyright 2005-2007 Rodolfo Giometti <giome...@linux.it>
Nov 15 19:17:41 pisces kernel: [ 102.195682] pps_core: source
pps-gpio.-1 got cdev (251:0)
Nov 15 19:17:41 pisces kernel: [ 102.195702] pps pps0: new PPS source
pps-gpio.-1
Nov 15 19:17:41 pisces kernel: [ 102.195745] pps pps0: Registered IRQ
194 as PPS source
Nov 15 19:17:41 pisces kernel: [ 102.470452] pps pps0: PPS event at
1353035851.050598985
Nov 15 19:17:41 pisces kernel: [ 102.470479] pps pps0: capture assert seq #1
my /etc/modules consists of:
loop
pps_gpio
my /etc/ntp.conf consists of:
# NEMA data on /dev/gps0
server 127.127.20.0 mode 48 minpoll 3 iburst prefer
fudge 127.127.20.0 flag1 0 time2 0.400
#PPS on /dev/pps0
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 flag3 1 flag4 1
/dev:
crw-rw---T 1 root dialout 204, 64 Nov 19 17:46 /dev/ttyAMA0
lrwxrwxrwx 1 root root 7 Dec 31 1969 /dev/gps0 -> ttyAMA0
crwxrwxrwt 1 root tty 251, 0 Nov 15 19:17 /dev/pps0
lrwxrwxrwx 1 root root 4 Nov 15 19:17 /dev/gpspps0 -> pps0
and this is what I am seeing in ntp:
ntpq -c lpeers
remote refid st t when poll reach delay offset jitter
==============================================================================
*GPS_NMEA(0) .GPS. 0 l 1 8 377 0.000
-55.452 9.778
oPPS(0) .PPS. 0 l 8 16 377
0.000 -0.001 0.001
+69.85.88.32 128.4.1.1 2 u 26 64 377 101.895
4.132 1.447
-irc.indoforum.o 64.147.116.229 2 u 37 64 377 18.260
4.336 2.875
-ntp1.ResComp.Be 128.32.206.55 3 u 51 64 377 38.992 6.287 2.307
+199.241.31.96 164.244.221.197 2 u 7 64 377 70.261
-21.524 3.039
I don't see any problems with the RPi creating the /dev/pps0 device on
startup and since I've done more RTFM I actually get good PPS data :)
I did contribute to the thread listed at the RPi forums but need to go
back and add what got it working for me. I also moved to a more
current kernel. I compiled a bunch of extra stuff in there as I want
to play with the networking stuff too so my kernel is not a small one.
uname -a
Linux pisces 3.6.1+ #1 Fri Nov 2 02:10:35 PDT 2012 armv6l GNU/Linux
James
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