[gpsd-dev] Skytraq binary support for Venus838

[Kai Harrekilde-Petersen]

Hello,

First of all sorry for being a bit verbose in my first mail to the list, 
but experience tells me that having more details help up front helps 
narrowing things down quicker.

I have been hacking away on Gary's Skytraq (Venus6) driver to get it to 
support the binary mode as well as baudrate and update rate changes (-s 
and -c) with some success.

The GNSS I have is a ZBTcom S1216F8 which contains a Venus838 module. I 
have mounted the module on a PCB connecting it to the GPIO connector on 
a Raspberry Pi 3. I have the 1PPS signal connected to a GPIO as well, 
which is picked up by the pps_gpio driver and used by gpsd.

In NMEA mode, the S1216 works out of the box (up to 50Hz fixes!) with 
the development code from Gary, even though it isn't recognized as a 
Skytraq (seems my module needed the magic wakeup cookie of 
"$Skytraq\n\r" before it would reply to messages).
If I turn on all messages (which is a lot), I get some previously 
un-handled/unknown sentences ("$GPDTM", "$GPGRS", and "$PSTI,003" ), 
which I promptly made driver_nmea0183.c ignore.

In binary mode, the S1216 only emits the "Navigation Data Message" 
(0xA8), which /should/ contain enough information to make gpsd happy 
(time, fixmode, num_sv, week, time of week [to at least 13bits], 
latitude, longitude, {ellipsoid,mean sea level} altitude, [gphv]dop, 
ECEF_[xyz], and ECEF_v[xyz]), but for some reason I don't get PVT data 
output to the client.
I'm computing/setting:
session->newdata.mode
session->gpsdata.status
mask = 
mode_SET|STATUS_SET|ONLINE_SET|SATELLITE_SET|TIME_SET|LATLON_SET|ALTITUDE_SETDOP_SET|ECEF_SET|VECEF_SET

It seems like [xc]gps wants the equivalent of GPGSA/GPGSV in order to be 
happy, and I haven't found a way of getting this data, outside going 
back to NMEA mode.

What am I missing to get things going?

Best regards,

Kai