[time-nuts] GPS Valid Fix Detector

[Yuri Ostry]

Hello,

Monday, November 24, 2008, 1:08:45, Peter Putnam wrote:

P> Greetings,

P> For those interested in a very simple means of determining if the NMEA
P> data stream from a GPS receiver contains valid fix data, I offer
P> design details for a "Valid Fix" detector that runs in a Microchip
P> 12F629, an 8-pin DIP device.

P> No other components are required if the GPS receiver provides CMOS 
P> output levels:

P> http://www.ni6e.com/time/GPS_Valid_Fix.html

P> Regards,
P> Peter


Looks like your firmware will need some correction, as there is a lot
of NMEA variations...

Below is examples of GPRMC sentences from several different GPS
receivers. You'll need to pick character after second comma, not by
particular offset, to be compatible. 


uBlox LEA4A (firmware 4):
$GPRMC,214541.00,A,5558.55936,N,03709.54595,E,1.116,104.33,120107,,,A*6A 

Trimble Pathfinder Pro XR
$GPRMC,050945.00,A,3504.227794,N,13545.810149,E,000.0,57.1,140302,6.5,W,A*12

Garmin GPS III Plus
$GPRMC,031655,A,3404.456,N,13531.788,E,000.0,360.0,110101,006.8,W*6D

Garmin GPSMAP 76S
$GPRMC,040014,A,4242.0410,N,14134.2795,E,1.4,51.0,010802,8.0,W,A*35

Blue Logger GPS (Something from Japan)
$GPRMC,021803.751,A,3501.5666,N,13546.9457,E,0.00,212.31,110604,,*07

uBlox SBR-LS (firmware 3.01)
$GPRMC,051250.00,A,5558.55523,N,03709.54211,E,1.177,229.34,080705,,,A*6E

GlobalSat BT-338 (SiRF)
$GPRMC,100643.000,A,5522.9036,N,03710.1282,E,0.16,119.11,200507,,*0D





-- 
Best regards,
 Yuri                          mailto:yuri at ostry.ru