[JonM]

I'll keep that in mind, but I think when I tried running gpsmon before it didn't have any effect.  I should have been tracking the version of gpsd, instead of the OS version, since that seems more important now.

I may start using the "--readonly" flag, so the gpsd doesn't try to modify the device.

[JonM]

Is there any chance that the ublox has a binary protocol, and somehow it's switched to that?

There isn't a getty running on the port.  This morning I noticed that even with binary data on the port, gpsd seems to be working.

SOLVED.... I just ran "gpsctl -n" and it's back to human readable NMEA sentences.

Have to wonder what caused the GPS receiver to switch into binary mode?

Thanks for the help!

[JonM]

I moved the BerryIMU-GPS to an older RPi2.. (running Raspian 8 - Jessie, with up to date firmware)

$ stty -F /dev/ttyAMA0
speed 9600 baud; line = 0;
-brkint -imaxbel

dmesg

3f201000.serial: ttyAMA0 at MMIO 0x3f201000 (irq = 114, base_baud = 0) is a PL011 rev2

and if I cat the serial port, I get the following:

Does any of this make sense:

$GNRMC,001817.00,V,,,,,,,030522,,,N*6A

$GNVTG,,,,,,,,,N*2E

$GNGGA,001817.00,,,,,0,00,99.99,,,,,,*77

$GNGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99*2E

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,00,txbuf alloc*61

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

$GNTXT,01,01,01,NMEA unknown msg*46

When moved back to the Pi3, dmesg:

3f215040.serial: ttyS0 at MMIO 0x3f215040 (irq = 71, base_baud = 50000000) is a 16550

$ stty -F /dev/serial0
speed 9600 baud; line = 0;
-brkint -imaxbel

and if I cat the port, I get garbage...

$ cat /dev/serial0
�b\('j
3�
�;pնn�Nb��� �\
t���J#Xq�b5�('j
-w�� �
$�'
#7� $"�0 "3=��!+E2 ^ٵb('j
�HUX��'?�� n
�b('j
^B��T���b('j
���� X?��b ('j
����)��ba('j

 

I need to find some wires to try a loopback test

[JonM]

Thanks Mark-

My original thought was that it was a problem with firmware and OS level, and that I cleared that up when I upgraded the Pi3B.  Then the problem came back.  The same firmware and OS are running on another Pi4, I just don't have physical access to it right now.  I'm going to try to find another Pi and swap the BerryIMU-GPS to that and see if the problem follows.  I'm also going to look and see if one of the solder joints might have been compromised.

[JonM]

Definitely leaning toward a hardware failure... I have a second nearly identical device that is working properly.  Its a Pi4, not a Pi3; otherwise software is identical.   Not easy to swap the BerryIMU-GPS cards to see if the problem follows the card.  Any other ways to try to diagnose?

[JonM]

The problem is probably not solved... there's been no software, firmware or operating system changes, and I'm back to having problems reading from the BerryIMU-GPS card.   I'll get a valid event from time to time, but not the once-per-second GPS report that I'm expecting.

[JonM]

More progress... ran rpi-update to update the firmware.  This was successful, and dmesg reported

ttyS0 at MMIO 0x3f215040 (irq=86, base_baud=50000000) is a 16550

This is same base_baud that was reported by Raspian 11 when it wasn't working.  The update also updated the kernel to 5.15.33.  Since cat /dev/serial0 was working, I went ahead and installed gpsd and gpsd-clients; as expected those worked too.

I went back to Raspian 11 with 5.15.32 (lower minor number?)

ttyS0 at MMIO 0x3f215040 (irq=71, base_baud=50000000) is a 16550

AND IT WORKED!  Sorry for yelling, but this is exciting!

Tempting fate, I ran rpi-update again, and ended up with the 5.15.34 kernel...

The GPS is still working!

If I had to guess, it was the firmware update that was needed to correspond to the 5.x series kernel.

[JonM]

Since updates are still available for Stretch, I updated to the 4.19.66 kernel, and can confirm that reading from /dev/serial0 still works, and I was able to install and configure gpsd too.

[JonM]

I've just been testing by running "cat /dev/serial0".  No reason to start gpsd if I can't see the NMEA sentences coming across the serial port!

I just downloaded Raspian 9 Stretch, with the 4.14.98 kernel and it works correctly.

Similar dmesg output:

ttyS0 at MMIO 0x0 (irq=166, base_baud=31250000) is a 16550

My conclusion is that something changed between Stretch and Buster.

[JonM]

More information; looks like something broke with newer Raspian releases.  I went back to Raspian 8 (Jesse) and the first thing I noticed was the dmesg output is different:

ttyS0 at MMIO 0x0 (irq=220, base_baud=31250000) is a 16550

If I recall, with Raspian 11, the base_baud was 50000000

I'm happy knowing the hardware is OK, but what is my path forward with newer Raspian releases?

[Author]

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