GPS not getting Fix beyond Mode=1

[nanunanu]

I have two of the Berry GPS-GSM modules and the first works great. Fixes to 3D quickly and maintains well.  The second unit will not fix beyond Mode 1 sitting next to the other with clear view to sky through window.  Both are setup to use external antenna and both have the same model antenna connected. Once is connected (sitting atop) a Pi Zero W and the other is atop a Pi 3.  Both are connected via GPIO for serial and using /dev/serial0 via GPSd service.  I attached the raw NMEA output for reference.

Is there any way to determine the status of the signal other than Mode of Fix?  Could it be an antenna issue?  What other things should I look for?

Attachments:

1. Berry-GPS-NMEA.txt

[nanunanu]

I tried another antenna.  No change.

I switched it back to internal; still no change.  Will not connect to Satellites.

[nanunanu]

So I swapped the 2 modules across the RPi units and the problem does not follow the Berry GPS-GSM module.  The 2 RPi are setup nearly identically.  What element of the connection between the RPi and the Berry could potentially cause the difference in performance?  I am getting between 2 and 3 Sats in view on the unit that is not getting a fix.  Makes me believe it is a signal strength issue?  Could it be a differential in power being supplied to the Berry?  Is it pulling from the 5V or 3.3V pin for power or from the UPS connection?

[nanunanu]

So the darn thing just got a fix and is mode 3.  I am still very concerned for the struggle.  I will go back into the documentation to see if enabling the ‘assist’ mode will not help.  Any advice on what could be impacting the performance would be appreciated non the less.

[Mark Williams]

The problem happens on one of your Pis? no matter which module is connected?

The power us pulled from 5v… there is a LDO which converts this to 3.3v for the GPS module annd 1.8V for GSM module.

It could be a power issue with one of your Pis
Try connecting it via USB only. You will have to access the NMEA sentences through the USB port. Instructions here:

https://ozzmaker.com/how-to-access-gps-nema-sentences-through-usb-on-the-berrygps-gsm/

If you still see the same problem, try increasing the current to the USB ports.
add the below line to /boot/config.txt
max_usb_current=1

Mark --OzzMaker.com --

[nanunanu]

And then it lost the fix.  🙁

[nanunanu]

OK.  Disconnected from GPIO and running on UPS Only.  Before changing boot/config.txt it is still not getting a fix after a few minutes.

Setup:

at
OK
AT+UGRMC=1
OK
AT+UGGLL=1
OK
AT+UGGSV=1
OK
AT+UGGGA=1
OK
AT+UGIND=1
OK
AT+UGPRF=1
OK
AT+UGPS=1,1,67
OK

+UUGIND: 0,67

+UUGIND: 1,0

Here are the raw NMEA strings.
$GNRMC,140809.00,V,,,,,,,280620,,,N*69
$GNGGA,140809.00,,,,,0,00,99.99,,,,,,*7C
$GPGSV,4,1,14,01,60,117,,03,00,137,,07,52,188,,08,28,055,*7C
$GPGSV,4,2,14,11,54,059,,13,15,298,,15,00,321,,17,27,248,*7B
$GPGSV,4,3,14,19,05,241,,22,09,118,,28,44,308,,30,65,254,*72
$GPGSV,4,4,14,46,19,245,,51,34,224,*72
$GLGSV,2,1,07,77,29,134,,78,81,075,,79,37,326,,81,50,219,*63
$GLGSV,2,2,07,82,02,216,,87,30,032,,88,72,030,*54
$GNGLL,,,,,140809.00,V,N*50
$GNRMC,140810.00,V,,,,,,,280620,,,N*61
$GNGGA,140810.00,,,,,0,00,99.99,,,,,,*74
$GPGSV,4,1,14,01,60,117,,03,00,137,,07,52,188,,08,28,055,*7C
$GPGSV,4,2,14,11,54,059,,13,15,298,,15,00,321,,17,27,248,*7B
$GPGSV,4,3,14,19,05,241,,22,09,118,,28,44,308,,30,65,254,*72
$GPGSV,4,4,14,46,19,245,,51,34,224,*72
$GLGSV,2,1,07,77,29,134,,78,81,075,,79,37,326,,81,50,219,*63
$GLGSV,2,2,07,82,02,216,,87,30,032,,88,72,030,*54
$GNGLL,,,,,140810.00,V,N*58

Changed bootconfig adding the max current param and repeated procedure.  Still no fix.  The other unit is sitting next to it by the window with a 3D fix.

I am going to move it over to a different Pi Zero to see what I get.  Will post results momentarily.

 

 

[nanunanu]

Well for some reason the darn Pi is not connecting to my WiFi but I can see that the GPS Fix LED is flashing on it.  So what the heck could be going on with my Pi 3 that would disrupt the GPS module.  This is crazy!

I am going to try another Pi 3 and see what happens.

[nanunanu]

Okay.  Twilight Zone here.  I connected the module to my Pi 3 on my bench (USB only) and fired it up.  It fixed in no time flat.  I am going to try the problem child again using the same USB cable I am using on my test bench Pi.  I will report back in a few.

[nanunanu]

So the problem continues with the Pi 3 that is my prototype unit.  The ONLY difference between it and my other RPi is that it carries a CAN bus module on its GPIO.  The CAN bus module does not use any conflicting GPIO pins however it is pulling power from the Pi.  I am using a 2.5Amp PS.  I also want to note that yesterday I took the two modules on a road trip (grocery store) and they both got a fix and performed equally on the trip.  The PS in the vehicle is actually rated slightly lower I think.  Confirmed.  Vehicle PS is 2.4Amp rating.  Looking at config files now to see what might be different.  It must be something to do with the mcp2515-can0 being active with the card sitting atop the pi because they both have the settings for the MCP2515 controller in the config.

Removing the card to see if that makes a difference.  The MCP2515 Controller using Ethernet for communications.  I don’t see why this would cause an issue with the GPS module?  Will post results shortly.

[nanunanu]

Card removed.  Still UPS only mode and still no GPS Fix.  This is absolutely nuts.  Any ideas on what about this Pi could be resulting in this would be greatly appreciated.  I am going to reassemble the unit put it in the vehicle and take a test drive again to confirm that it is working in that environment.  I think I will power it with my battery pack so that I can start and end the trip in my office space down here in the basement to see how it reacts in the move from here to the car and back.  I will report in on the results in a little while.

[nanunanu]

OK.  So the GPS Fixed once I got outside and stayed fixed right up until I came back inside and brought it down stairs.  So what about this RPi would affect the strength of RX/TX of the module? Picture of unit attached.

Any idea appreciated.

Attachments:

1. 

   IMG_Prototype-scaled.jpg
   

[Mark Williams]

you ruled out the MCP2515. What about the display? do you get the same issue if the display is not connected?

Do you get issues with the GSM module? does it stay connected when you have problems with the GPS?

The only thing i can think off is an unstable power supply.. or not enough power. But 2.5A should be enough.
Does the problem follow the power supply around?

Mark --OzzMaker.com --

[nanunanu]

The display has a separate power switch and has been turned off the entire time I am testing.  It is there to support the end product but is not needed for this function so I leave it turned off and monitor through ssh session.  I do not believe it is the PS because I am pretty sure I powered it from my 12V power pack (2000Mah NMH) regulated to 5.2V on the USB power connection to the RPi.  I will confirm that shortly and let you know.

I am finding some issues with the GSM connection when I take the unit on a road trip; however, this looks to be more like issues with the hologram python SDK.  I am working on that now and have no reason to believe that there is any issue with the GSM connection there.  BTW; future plans for LTE for the Berry GPS-GSM???  🙂

[nanunanu]

Sorry for the time lapse silence.  I have been testing and wanted to give you a final solid update.

I cycled my problem Berry unit through 3 RPi 3 boards with no success.  I have tested with clear view to sky.  I placed the unit back atop my second Pi Zero W and it works.  Granted it does not fix as easily as the original Berry atop another Pi Zero W but it works and works pretty well.  Both units maintained 3D fix consistently on a road trip around town and through a wooded area (Park like).

So I took the original Berry off the Pi Zero and put it on the RPi3 and sure enough it linked up pretty well getting to a 3D fix in a minute or less.  Outside with clear view of course.  So it is definitely an issue with the combo of the second Berry Unit and the RPi3 units.

The only thing I did with the Berry was to solder the pin socket on as required.  I am not a novice at soldering but I also do not have high end (temp reg) equipment.  I use a standard Weller Soldering Iron for my work.  I don’t remember if it is 25 or 30 Watt.  Given that I tested all RPi3 with USB only I would question if a soldering issue could be in play?  Should I re-solder the joints?  Could I have slightly damaged it in the soldering?  I tend to leave cold joints as opposed to over heating but anything is possible.

A final update with you thoughts on this issue would be appreciated.

PS> LTE in the future?  Why is the GPS-GSM no longer on Amazon?  Why was it cheaper on Amazon?

Thanks

Brian

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