[gpsd-users] u-blox binary time issue

[Deven Hickingbotham]

Gary,

Last year we discussed an issue with missing fixes from a u-blox 7 
receiver.  Since then I've been trying various solutions, but 
concentrating on using the u-blox binary protocols.

To get gpsd 3.16 (Raspbian) working with u-blox I have to run gpsd with 
the -b option otherwise gpsd always turns on the NMEA messages.

For gpsd to be fully functional (meaning cgps works), I have to use 
u-blox's PVT, SOL, and SVINFO messages.  Anything less and cgps is 
missing data.

I have a Python app that calculates the gps latency and it is generally 
0.1 seconds.  BTW, I use chrony set set my system clocks.

But after configuring the u-blox receiver to deliver only binary 
messages, the latency was -0.9 seconds (meaning the gps timestamp was 
ahead of the system time).  This is exactly one second off from what it 
should be.

I tried setting different gps update rates (1 second and 0.25 seconds) 
and the latency was still -0.9.

When I switch the u-blox back to only NMEA messages, latency returns to 
normal.  This is without rebooting, so the system clock is the same for 
all calculations.

I tested using both u-blox 7 and 8 receivers.

Any idea what might be going on?

Deven