My PPS output from ultimate GPS shield does output correctly

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tisvesalem
 
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My PPS output from ultimate GPS shield does output correctly

Post by tisvesalem »

Hi,
so I just recently bought an adafruit ultimate gps brekout v3
https://learn.adafruit.com/downloads/pd ... te-gps.pdf
and I wanted to use the PPS output to have correct timing. However, when I measured the output of the NMEA (tx pin) and the PPS, all I saw were the NMEA pulses and nothing on the PPS.

when I tried an ADC circuit with 10 bit depth and plotted it in MATLAB I got pulses around 14mV high with a pulse duration that was definitely not 50ms as the datasheet describes it to be. Can someone help?

P.s. If you think it is the code I am currently using, I have attempted to get the PPS with the example codes that come with the Adafruit_GPS library yet still no avail

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Franklin97355
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by Franklin97355 »

Are you getting good NMEA strings from the GPS when you direct connect or use the parsing sketch?

tisvesalem
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by tisvesalem »

Yes I am getting good NMEA strings.
I wanted to see if the rising edge of the NMEA strings and the PPS matched up to see if the clocks are synchronized.

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Franklin97355
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by Franklin97355 »

I'm not sure the PPS is synced to anything but just goes high once a second.

tisvesalem
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by tisvesalem »

I want to see if it syncs, the problem is that I don't see the high signal at all

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Franklin97355
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by Franklin97355 »

Could you show how it is connected?

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adafruit_support_mike
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by adafruit_support_mike »

The rising edge of the PPS signal is synced to the beginning of each GPS second, which is spec'd to be within 10 nanoseconds ot standard time. IIRC, the pulse lasts 10 milliseconds.

tisvesalem
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by tisvesalem »

How much voltage with the pulse be?
We had 14 mV in a pulse-like manner but it seemed like it was just noise

tisvesalem
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by tisvesalem »

franklin97355 wrote:Could you show how it is connected?
Well I am just trying to see how the PPS looks like on an oscilloscope.
What I am getting is not a 10ms long pulse,
I am getting a pulse that is a fraction of that with a 14mV magnitude which allows me to presume it is just noise

ALSO the specifications on the ultimate gps breakout I have says that the PPS should be 50ms long...
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adafruit_support_mike
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by adafruit_support_mike »

The PPS pulse should be the same as the module's supply voltage.

The module will only emit PPS after it has a fix though. Double-check your NMEA sentences to see if you're getting coordinates for at least three sattelites.

tisvesalem
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by tisvesalem »

Yes, tried that.
I also tried getting the PPS with an example sketch after getting a fix
still no avail

tisvesalem
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by tisvesalem »

I really need help on this,
I am getting a fix and the gps is logging quite fine when it has a fix
the only problem is getting a PPS output
The VIN I am using is a 9V battery and I am sure that should be sufficient enough to have a significant PPS signal
and yes, I have replace the 9V battery so it is fully charged
Thank you guys :)

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adafruit_support_mike
 
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Re: My PPS output from ultimate GPS shield does output corre

Post by adafruit_support_mike »

Let's try a new module.

Send a note to [email protected] with a link to this thread and the folks there will get you a replacement.

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