PPS signal of ultimate gps 3 unusable suddenly

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flok
 
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PPS signal of ultimate gps 3 unusable suddenly

Post by flok »

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

Post by flok »

Tried a different antenna as well and a different location (both times with clear view of the sky) and it made no difference.

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sj_remington
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by sj_remington »

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

flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by flok »

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

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adafruit_support_mike
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by adafruit_support_mike »

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?

flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by flok »

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.

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adafruit_support_mike
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by adafruit_support_mike »

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

flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by flok »

It follows. I swapped raspberry's and antenna's.

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adafruit_support_mike
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by adafruit_support_mike »

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?

flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by flok »

At least(!) more than 5 years ago.

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adafruit_support_mike
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by adafruit_support_mike »

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.

flok
 
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Re: PPS signal of ultimate gps 3 unusable suddenly

Post by flok »

Thank you. I'll see if I can find a windows pc for that.
I'll let you know if it helped.

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