[chrony-users] Two nearly identical boxes behaving differently

[Paul J R <me@xxxxxx>]

Hi all,

Using chrony 3.1 with gps and pps.

i've got two little routers (AR9331 based boxes) that are identical but 
for two things:

1) different ip addresses/hostname

2) different gps chips (ones a Quectel L80, the other is the MTK3339)

They're running an openwrt firmware that i've custom compiled for my 
needs but they're both having issues I just cant figure out.

The config on both is identical:

    refclock SHM 0 offset 0.395 delay 0.2 refid NMEA noselect
    refclock PPS /dev/pps0 refid PPS poll 4 prefer lock NMEA
    server 10.69.69.1

One cant seem to poll pps:

root@ntp03:~# chronyc sources
210 Number of sources = 3
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#? NMEA                          0   4   377    10 -264ms[ -264ms] +/-  
110ms
#? PPS                           0   4     0     - +0ns[   +0ns] +/-    0ns
^* 10.69.69.1                    2   6   177    46 -4689ns[  -14us] 
+/-   92ms

And the other cant poll the server:

root@ntp04:~# chronyc sources
210 Number of sources = 3
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
#? NMEA                          0   4   377    19    -24ms[ -24ms] +/-  
105ms
#* PPS                           0   4   277    18    +39ns[ -5ns] +/-   
56ns
^? 10.69.69.1                    0   7   377     -     +0ns[ +0ns] 
+/-    0ns

Both can happily ping the server (which is actually the gateway), both 
seem to be able to poll the gpsd, both are connected to the same network 
and are even in the same switch, and both have a working pps line:

root@ntp03:~# ppstest /dev/pps0

trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1510241218.002956935, sequence: 1525 - clear 
0.000000000, sequence: 0
source 0 - assert 1510241219.002954396, sequence: 1526 - clear 
0.000000000, sequence: 0

root@ntp04:~# ppstest /dev/pps0
trying PPS source "/dev/pps0"
found PPS source "/dev/pps0"
ok, found 1 source(s), now start fetching data...
source 0 - assert 1510241194.000000503, sequence: 1490 - clear 
0.000000000, sequence: 0
source 0 - assert 1510241195.000000044, sequence: 1491 - clear 
0.000000000, sequence: 0

But I just cant seem to find a reason why they're both showing different 
problems (thought the issue polling the server may be the server itself 
not responding to one of them as other servers do work with both).

I should also say that the kernel is based on my own pps code which is 
in turn based on the gpio interupt code for the AR9331, though as yet i 
cant find a fault with either of those patches.

Any hints anyone can give me on how to debug this would be really handy?



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