ugps: add quality measurement parameters

The current version of ugps does not report any quality parameters for
GPS receiver fixation. Considering the positioning error, which can be
up to hundreds of meters, it is helpful to know how accurately the GPS
determines the position.

This PR supports determining the number of satellites and the HDOP
(Horizontal Dilution of Precision) parameter to address this.  The GPGGA
sentence is already parsed in the code, so it just extends the amount of
data it reads.

Fixes: #2 (ugps miss GPS quality parameters)
Signed-off-by: Zbynek Kocur <zbynek.kocur@fel.cvut.cz>
Signed-off-by: Petr Štetiar <ynezz@true.cz> [whitespace fixes, long line wrap]

3 files changed, 13 insertions, 3 deletions

diff --git a/main.c b/main.c
index f67470e..acd6a42 100644
--- a/main.c
+++ b/main.c
@@ -66,6 +66,10 @@ gps_info(struct ubus_context *ctx, struct ubus_object *obj,
 			blobmsg_add_string(&b, "course", course);
 		if (gps_fields & GPS_FIELD_SPD)
 			blobmsg_add_string(&b, "speed", speed);
+		if (gps_fields & GPS_FIELD_SAT)
+			blobmsg_add_string(&b, "satellites", satellites);
+		if (gps_fields & GPS_FIELD_HDP)
+			blobmsg_add_string(&b, "HDOP", hdop);
 	}
 	ubus_send_reply(ctx, req, b.head);
 
diff --git a/nmea.c b/nmea.c
index e86f68f..195753e 100644
--- a/nmea.c
+++ b/nmea.c
@@ -52,7 +52,7 @@ struct nmea_param {
 } nmea_params[MAX_NMEA_PARAM];
 
 static int nmea_bad_time;
-char longitude[33] = { 0 }, latitude[33] = { 0 }, course[17] = { 0 }, speed[17] = { 0 }, elevation[17] = { 0 };
+char longitude[33] = { 0 }, latitude[33] = { 0 }, course[17] = { 0 }, speed[17] = { 0 }, elevation[17] = { 0 }, satellites[3] = { 0 }, hdop[5] = { 0 };
 int gps_valid = 0;
 char gps_fields = 0;
 
@@ -222,8 +222,12 @@ nmea_gga_cb(void)
 {
 	if (!gps_valid)
 		return;
+	strncpy(satellites, nmea_params[7].str, sizeof(satellites));
+	strncpy(hdop, nmea_params[8].str, sizeof(hdop));
 	strncpy(elevation, nmea_params[9].str, sizeof(elevation));
-	gps_fields |= GPS_FIELD_ALT;
+	gps_fields |= GPS_FIELD_SAT | GPS_FIELD_HDP | GPS_FIELD_ALT;
+	DEBUG(4, "satellites: %s\n", satellites);
+	DEBUG(4, "HDOP: %s\n", hdop);
 	DEBUG(4, "height: %s\n", elevation);
 }
 
diff --git a/nmea.h b/nmea.h
index 2de06dc..91a41eb 100644
--- a/nmea.h
+++ b/nmea.h
@@ -23,7 +23,7 @@
 
 #include <libubox/ustream.h>
 
-extern char longitude[33], latitude[33], course[17], speed[17], elevation[17];
+extern char longitude[33], latitude[33], course[17], speed[17], elevation[17], satellites[3], hdop[5];
 extern int nmea_open(char *dev, struct ustream_fd *s, speed_t speed);
 extern void gps_timestamp(void);
 extern unsigned int adjust_clock;
@@ -33,5 +33,7 @@ extern char gps_fields;
 #define GPS_FIELD_COG (1<<2)
 #define GPS_FIELD_SPD (1<<3)
 #define GPS_FIELD_ALT (1<<4)
+#define GPS_FIELD_SAT (1<<5)
+#define GPS_FIELD_HDP (1<<6)
 
 #endif