[LinuxPPS] Why is my ATOM clock a falseticker?

[Paul Simons]

First, this list is great.  Thank you for your conversation and willingness to share.  I took my Truetime 486-DC to a hardware type and he hooked a oscilloscope to the pps and declared it a decent RS232 signal (0/+5v, 200ms).  I stopped playing with the parallel port and wired it directly to the serial port.  I applied Folkert's patch to ppsldisc.  I downloaded and built the latest NTP (4.2.5p157) with the right timex.h and against librt:

# ntptime
ntp_gettime() returns code 0 (OK)
  time cd2da60d.47870528  --- --- -- ---- --:--:--, (.279404614),
  maximum error 40615 us, estimated error 31 us, TAI offset 0
ntp_adjtime() returns code 0 (OK)
  modes 0x0 (),
  offset -145.309 us, frequency -93.211 ppm, interval 1 s,
  maximum error 40615 us, estimated error 31 us,
  status 0x2001 (PLL,NANO),
  time constant 6, precision 0.001 us, tolerance 500 ppm,

I can "watch -n1 cat /sys/class/pps/pps*/{clear,assert}" and count the happy little pulses:  (from dmesg):

PPS event on source 1 at 1233330677.993769228
capture assert seq #76086 for source 1
[IRQev] PPS assert at 615823466 on source #1
PPS_FETCH: source 1
timeout 0.000000000
PPS event on source 1 at 1233330678.493769677
capture clear seq #76087 for source 1
[IRQev] PPS clear at 615823591 on source #1
PPS event on source 1 at 1233330678.993769372
capture assert seq #76087 for source 1
[IRQev] PPS assert at 615823716 on source #1
PPS_FETCH: source 1
timeout 0.000000000
PPS event on source 1 at 1233330679.493769893
capture clear seq #76088 for source 1
[IRQev] PPS clear at 615823841 on source #1
PPS event on source 1 at 1233330679.993769569
capture assert seq #76088 for source 1
[IRQev] PPS assert at 615823966 on source #1
PPS_FETCH: source 1
timeout 0.000000000
PPS event on source 1 at 1233330680.493770702
capture clear seq #76089 for source 1
[IRQev] PPS clear at 615824091 on source #1
PPS event on source 1 at 1233330680.993768984
capture assert seq #76089 for source 1
[IRQev] PPS assert at 615824216 on source #1
PPS_FETCH: source 1
timeout 0.000000000

And yet, for all that, I get:

# ntpq -c ass

ind assid status  conf reach auth condition  last_event cnt 

=========================================================== 

  1 49470  914a   yes   yes  none falsetick    sys_peer  4 

  2 49471  962a   yes   yes  none  sys.peer    sys_peer  2# ntpq -c peer

     remote           refid      st t when poll reach   delay   offset  jitter 

============================================================================== 

xPPS(1)          .PPS.            0 l   13   16  201    0.000  -493.77   0.003 

*TRUETIME(0)     .TRUE.           0 l   59   64  377    0.000   -0.159   0.030
and:

# ntpq -c assoc

ind assid status  conf reach auth condition  last_event cnt 

=========================================================== 

  1 49470  914a   yes   yes  none falsetick    sys_peer  4 

  2 49471  911b   yes   yes  none falsetick clock_alarm  1# ntpq -c peer

     remote           refid      st t when poll reach   delay   offset  jitter 

============================================================================== 

xPPS(1)          .PPS.            0 l  100   16  300    0.000  -493.74   0.002 

xTRUETIME(0)     .TRUE.           0 l   34   64  377    0.000   -0.122   0.034
And this after running for twelve hours.


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