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PPS signal of ultimate gps 3 unusable suddenly
Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.

PPS signal of ultimate gps 3 unusable suddenly

by flok on Thu Dec 02, 2021 5:34 pm

Hi,

I have connected to a raspberry pi an adafruit ultimate gps 3.
Suddenly the pps signal is (compared to other gps'es and ntp servers on the internet) several 100ms mis-ticking.
I thought it could be broken so I took an other adafruit ultimate gps 3: same problem.
Then I swapped the raspberry pi: same problem.
What could be the cause? Both gpses broken? Or?
flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

by flok on Sat Dec 04, 2021 4:09 pm

Tried a different antenna as well and a different location (both times with clear view of the sky) and it made no difference.
flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

by sj_remington on Sun Dec 05, 2021 12:12 am

Does the GPS have a satellite fix? Record some NMEA sentences and post them (RMC type is enough).

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Re: PPS signal of ultimate gps 3 unusable suddenly

by flok on Sun Dec 05, 2021 7:00 am

It does:

(71) $GPGGA,105757.000,5201.6746,N,00441.7433,E,1,7,1.24,4.8,M,47.1,M,,*54
(56) $GPGSA,A,3,05,09,07,02,14,20,30,,,,,,1.51,1.24,0.86*03
(70) $GPRMC,105757.000,A,5201.6746,N,00441.7433,E,0.60,8.87,051221,,,A*6C
(35) $GPZDA,105757.000,05,12,2021,,*50
flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

by adafruit_support_mike on Sun Dec 05, 2021 9:41 pm

It's very unlikely to have multiple random failures that all behave the same way.

The first thing I'd suspect would be a software issue. Did you change or update/upgrade any code since the last time the PPS worked as expected?

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Re: PPS signal of ultimate gps 3 unusable suddenly

by flok on Tue Dec 07, 2021 2:16 pm

Well, I have 4 raspberry pi's that all run the same ntpsec (ntpd, and gpsd where applicable). Now only the pi's with the adafruit shield show this odd behaviour.
flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

by adafruit_support_mike on Tue Dec 07, 2021 11:14 pm

If you swap the GPS module from one RasPi to another, does the problem follow the module or stay with the RasPi?

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Re: PPS signal of ultimate gps 3 unusable suddenly

by flok on Wed Dec 08, 2021 11:19 am

It follows. I swapped raspberry's and antenna's.
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Re: PPS signal of ultimate gps 3 unusable suddenly

by adafruit_support_mike on Wed Dec 08, 2021 8:25 pm

Thank you.

This is the first time I've heard of a GPS module's PPS falling out of sync with the constellation's clock. When did you get the GPS modules?

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Re: PPS signal of ultimate gps 3 unusable suddenly

by flok on Sat Dec 11, 2021 1:40 am

At least(!) more than 5 years ago.
flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

by adafruit_support_mike on Sat Dec 11, 2021 10:34 pm

At that age, it could be almost anything.

The fact that you're seeing the same issue in two modules suggests a problem that might be related to firmware, so you can try updating that:

https://learn.adafruit.com/adafruit-ult ... aq-2954734

I can't make any promises, but it can't hurt.

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Re: PPS signal of ultimate gps 3 unusable suddenly

by flok on Sun Dec 12, 2021 8:07 am

Thank you. I'll see if I can find a windows pc for that.
I'll let you know if it helped.
flok
 
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Please be positive and constructive with your questions and comments.