[gpsd-users] Communication loss with GR-701W

[Benoît Thébaudeau]

Hi,

I'm using a Navisys GR-701W (u-blox 7, USB PL2303 interface) with gpsd 3.18, 
PPS, and ntp 4.2.8p13.

Most of the time, this setup works fine, but from time to time, after 
hotplugging the GR-701W module, gpsd switches to the UBX protocol, then gpsd no 
longer indicates any received packets, as if the module became quiet. The PPS 
continues to work fine, though (and the LED of the module blinks normally). 
When this happens, right before the issue, gpsd reports a warning containing an 
error, apparently sent by the module. I cannot post the exact log right now, 
but this warning looks like this:
gpsd:WARN: TXT: trk tick error[...]

Restarting gpsd does not help. In this case, gpsd starts directly with UBX, and 
the PPS still works, but that's all.

The only straightforward way of recovering from this issue is to replug the 
module.

Any idea about how to fix this? I don't know if it's caused by gpsd doing 
something that the module does not like, or if it's the module that gets 
confused on its own.

I have a few ideas to debug this using the gpsd debug log, gpsmon, a USB 
sniffer, or ubxtool/u-center, but it won't be easy if it's something going on 
inside the module. Perhaps sending a hot hardware reset command to the module 
could be a good workaround.

I will post an update when I have more information.

Thanks in advance.

Best regards,
Benoît