[time-nuts] Thunderbolt meets ntpd
Tim Cwik
timenuts at stnhbr.com
Mon Jun 23 08:36:23 EDT 2008
Chris Kuethe wrote:
> On Sun, Jun 22, 2008 at 11:30 PM, Hal Murray <hmurray at megapathdsl.net> wrote:
>
>> Does anybody have any Linux code to print the stuff it's sending? If not,
>> I'll probably have something soon.
>>
>
> 1) dig around on trimble.com - there's a link to iQSource.zip which
> may be useful
> 2) rip some code from gpsd - we can decode a fair number of the
> packets, and there's a lot of machinery you can reuse.
>
> I think I ordered early enough that sometime in the coming weeks a
> thunderbolt will be headed my way, after that i can see about making
> gpsd do the right things. already i know i need to do auto parity
> detection - we assume TSIP is 8O1, which may not be true in the case
> of the thunderbolt. Given some of this past week's list traffic, I
> think Trimble goofed if they decided to go to 8N1.
>
>
Hi Chris,
Trimble is using 8N1. Patching the code as you suggested works. To keep
gpsd as config free as possible, I suppose you will need the auto parity
detection.
I used the patch Wayne Knowles provided for decoding the super packet
and that allows gpsd to detect when it has a fix.
The PPS output from the Thunderbolt I have is a short negative going
pulse. The documentation says the pulse is configurable but I could not
find a way to do this using Tboltmon. Instead, I purchased a FATPPS kit
from TAPR which is able to stretch the PPS pulse and can also invert the
polarity. Using the FATPPS, your parity correction, and Wayne's patch, I
now have ntpd using the PPS from the Thunderbolt.
ntpd rejects the GPS clock itself. I am still trying to understand this.
I hope when your unit arrives, the fix will be obvious to you. Here are
my results:
ind assID status conf reach auth condition last_event cnt
===========================================================
1 15949 9314 yes yes none outlyer reachable 1
2 15950 9414 yes yes none candidat reachable 1
3 15951 9314 yes yes none outlyer reachable 1
4 15952 9414 yes yes none candidat reachable 1
5 15953 8015 yes yes none reject clock expt 1
6 15954 9614 yes yes none sys.peer reachable 1
7 15955 9014 yes yes none reject reachable 1
ind assID status conf reach auth condition last_event cnt
===========================================================
1 15949 9314 yes yes none outlyer reachable 1
2 15950 9414 yes yes none candidat reachable 1
3 15951 9314 yes yes none outlyer reachable 1
4 15952 9414 yes yes none candidat reachable 1
5 15953 8015 yes yes none reject clock expt 1
6 15954 9614 yes yes none sys.peer reachable 1
7 15955 9014 yes yes none reject reachable 1
Thanks for all of your help through several versions of gpsd. I am quite
excited to finally have this sort of time reference available at home!
Best regards,
Tim
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