nmea: parse $GPGLL sentences for position

Some GPS receivers do not send $GPGGA sentence. Parse latitude and
longitude also from $GPGLL sentences.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

diff --git a/nmea.c b/nmea.c
index 5bf6d9af7124a8d82528c44ee57aaacea0316c73..d51d936d2e69bcae34804a93d23d7f8df165c230 100644 (file)
--- a/nmea.c
+++ b/nmea.c
@@ -94,6 +94,34 @@ do_adjust_clock(struct tm *tm)
        }
 }
 
+static void
+parse_gps_coords(char *latstr, char *vhem, char *lonstr, char *hhem)
+{
+       float minutes;
+       float degrees;
+       float lat = strtof(latstr, NULL);
+       float lon = strtof(lonstr, NULL);
+
+       degrees = floor(lat / 100.0);
+       minutes = lat - (degrees * 100.0);
+       lat = degrees + minutes / 60.0;
+
+       degrees = floor(lon / 100.0);
+       minutes = lon - (degrees * 100.0);
+       lon = degrees + minutes / 60.0;
+
+       if (*vhem == 'S')
+               lat *= -1.0;
+       if (*hhem == 'W')
+               lon *= -1.0;
+
+       snprintf(latitude, sizeof(latitude), "%f", lat);
+       snprintf(longitude, sizeof(longitude), "%f", lon);
+
+       DEBUG(3, "position: %s %s\n", latitude, longitude);
+       gps_timestamp();
+}
+
 static void
 nmea_rmc_cb(void)
 {
@@ -132,29 +160,7 @@ nmea_rmc_cb(void)
                ERROR("lat/lng have invalid string length %zu<9, %zu<10\n",
                       strlen(nmea_params[3].str), strlen(nmea_params[5].str));
        } else {
-               float minutes;
-               float degrees;
-               float lat = strtof(nmea_params[3].str, NULL);
-               float lon = strtof(nmea_params[5].str, NULL);
-
-               degrees = floor(lat / 100.0);
-               minutes = lat - (degrees * 100.0);
-               lat = degrees + minutes / 60.0;
-
-               degrees = floor(lon / 100.0);
-               minutes = lon - (degrees * 100.0);
-               lon = degrees + minutes / 60.0;
-
-               if (*nmea_params[4].str == 'S')
-                       lat *= -1.0;
-               if (*nmea_params[6].str == 'W')
-                       lon *= -1.0;
-
-               snprintf(latitude, sizeof(latitude), "%f", lat);
-               snprintf(longitude, sizeof(longitude), "%f", lon);
-
-               DEBUG(3, "position: %s %s\n", latitude, longitude);
-               gps_timestamp();
+               parse_gps_coords(nmea_params[3].str, nmea_params[4].str, nmea_params[5].str, nmea_params[6].str);
        }
 }
 
@@ -163,7 +169,8 @@ nmea_zda_cb(void)
 {
        struct tm tm;
 
-       gps_valid = 1;
+       if (!gps_valid)
+               return;
 
        memset(&tm, 0, sizeof(tm));
        tm.tm_isdst = 1;
@@ -193,6 +200,20 @@ nmea_zda_cb(void)
        do_adjust_clock(&tm);
 }
 
+static void
+nmea_gll_cb(void)
+{
+       if (*nmea_params[6].str != 'A') {
+               gps_valid = 0;
+               DEBUG(4, "waiting for valid signal\n");
+               return;
+       }
+
+       gps_valid = 1;
+
+       parse_gps_coords(nmea_params[1].str, nmea_params[2].str, nmea_params[3].str, nmea_params[4].str);
+}
+
 static void
 nmea_gga_cb(void)
 {
@@ -230,6 +251,10 @@ static struct nmea_msg {
                .msg = "GGA",
                .cnt = 14,
                .handler = nmea_gga_cb,
+       }, {
+               .msg = "GLL",
+               .cnt = 7,
+               .handler = nmea_gll_cb,
        }, {
                .msg = "VTG",
                .cnt = 9,