When I got a wintec g-rays2, it didn't work on USB out of the box with whatever laptop I had (probably a macbook), but was OK on Bluetooth, so that's what I stuck with.
Now, eight years later, I plugged it into one of my Raspberry Pis and it appears as /dev/ttyUSB1 by magic!
Getting NMEA sentences in minicom
minicom --device=/dev/ttyUSB1 --baud=4800 gives some garbled stuff every second, so I'm receiving the
NMEA sentences but at the wrong serial port settings.
The manual didn't give any help but a bit of fiddling reveals sensible looking output at 57600 baud, 8N1 (here you can see where I live).
$GPRMC,121815.000,A,5130.3697,N,00003.7216,W,0.00,148.43,240717,,,A*72 $GPGGA,121815.000,5130.3697,N,00003.7216,W,1,05,2.9,46.2,M,47.0,M,,0000*70 $GPGSA,A,3,21,26,31,27,16,,,,,,,,4.3,2.9,3.2*38 $GPGSV,3,1,12,05,03,021,28,10,08,157,19,21,67,086,34,26,69,175,39*7C $GPGSV,3,2,12,29,12,083,,07,08,333,,31,06,193,26,20,27,059,24*72 $GPGSV,3,3,12,49,,,35,27,43,274,31,16,72,283,39,18,26,132,23*4D
These lines are spewed out once a second without needing to send any start command to the GPS unit.
Getting ntpd to pay attention
$GPGGA are the relevant sentences for ntpd, according to the manual.
I already have ntpd runnning on this Pi, with an MSF receiver configured already.
This gives a /dev/gps0 (at least until reboot):
cd /dev sudo ln -s ttyUSB1 gps0
and this line in
/etc/ntpd.conf makes ntpd look for NMEA time sentences on /dev/gps0:
server 127.127.20.0 mode 67
The mode, decimal 67, means hexadecimal 0x43: 0x01 listen for GPRMC, 0x02 listen for GPGGA, 0x40 use 57600 baud.
And after a restart, tada! (although apparently a 160ms delay compared to all my other time sources. ick)
pi@faeroe /dev $ ntpq --peers remote refid st t when poll reach delay offset jitter ============================================================================== 2001:8b0:1638:9 184.108.40.206 2 u 39 64 17 0.952 157.794 0.783 ntp2.aa.net.uk 220.127.116.11 2 u 41 64 17 14.923 162.505 0.671 SHM(2) .MSF. 0 l - 64 0 0.000 0.000 0.000 *GPS_NMEA(0) .GPS. 0 l 55 64 7 0.000 -5.660 0.819 tyne.cqx.ltd.uk 18.104.22.168 2 u 46 64 17 0.674 157.858 0.759