no gnss fix

[pbljung]

Hi, I don’t get a GNSS fix from my new BerryGPS-IMU v4 board connected to a Rpi ZeroW. Testing was static with device on a table outside under a clear sky. Switch is on INT for internal antenna.

Attached are 3 screenshots from gpsmon (after Rpi reboot it shows ublox, if you CtrlC and restart gpsmon it shows nmea) and cgps. The gpsmon with ublox screenshot shows a correct position but no velocities or DOP while cgps shows “NO FIX”.

I can see the nmea sentences using “gpspipe -r”. I enabled NMEA logging, and visualizers show a single spot (not a cluster or path). In the log I can see multiple GPRMC messages with LLA
$GPRMC,225248,V,3750.7593,N,12214.1109,W,0.0000,0.000,131122,,*25
I expected to see PVT messages but find none.

Is this expected behavior?
Thanks!

.ps I have tested the LSM6DSL, LIS3MDL and BMP388 and they all work ok.

Attachments:

1. 

   Screen-Shot-2022-11-13-at-1.41.37-PM.png
   

2. 

   Screen-Shot-2022-11-13-at-1.47.48-PM.png
   

3. 

   Screen-Shot-2022-11-13-at-1.49.38-PM.png
   

[Mark Williams]

Hi, PVT is for NMEA 1.5 .  Ublox uses NMEA 2.0 which has no PVT.  Can you use RMC?

When you try and start gpsmon without any switches, it will try and workout what GNSS device is attached and use a direct driver.   you can use gpsmon -n to force it to use NMEA

Mark --OzzMaker.com --

[pbljung]

Hi Mark
OK useful info, but how do I get a fix in a reasonable amount of time?

Your datasheet suggests <27 sec to a fix but I have let the BerryGPS-IMU run for hours on separate days without getting a fix (outside, no obstructions). The poor indicated S/N makes me wonder if there is an antenna or hw rf issue. Is each GPS receiver tested?

[Mark Williams]

For <27  that would be for a warm start from previously having a fix… and if no power is lost to the GPS. (this is why there is a superCap included which should last for 1-2 hrs proving battery backup to the GPS.)

It usually takes between 10-30 mins for first time to fix.

We test every unit to see that data is received over serial.  We then test every 10th for GPS, using an external antenna.
Can you share a close up photo of the top half of the board, i want to make sure nothing is missing

 

Mark --OzzMaker.com --

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