Convert GPS to SiRF binary protocol.

This switches the GPS unit from NMEA to SiRF protocol at startup and then
parses the binary data. The binary data uses a different encoding of lat/lon
than the NMEA strings, and so the telemetry and eeprom data formats change
with this switch.

Signed-off-by: Keith Packard <keithp@keithp.com>

1 files changed, 34 insertions, 10 deletions

diff --git a/src/ao_gps_print.c b/src/ao_gps_print.c
index 4dced8f1..bef87aea 100644
--- a/src/ao_gps_print.c
+++ b/src/ao_gps_print.c
@@ -17,26 +17,50 @@
 
 #include "ao.h"
 
+struct ao_gps_split {
+	uint8_t positive;
+	uint8_t	degrees;
+	uint8_t	minutes;
+	uint16_t minutes_fraction;
+};
+
+static void
+ao_gps_split(int32_t v, __xdata struct ao_gps_split *split) __reentrant
+{
+	uint32_t minutes_e7;
+
+	split->positive = 1;
+	if (v < 0) {
+		v = -v;
+		split->positive = 0;
+	}
+	split->degrees = v / 10000000;
+	minutes_e7 = (v % 10000000) * 60;
+	split->minutes = minutes_e7 / 10000000;
+	split->minutes_fraction = (minutes_e7 % 10000000) / 1000;
+}
+
 void
 ao_gps_print(__xdata struct ao_gps_data *gps_data) __reentrant
 {
 	printf("GPS %2d sat",
 	       (gps_data->flags & AO_GPS_NUM_SAT_MASK) >> AO_GPS_NUM_SAT_SHIFT);;
 	if (gps_data->flags & AO_GPS_VALID) {
+		static __xdata struct ao_gps_split	lat, lon;
+		ao_gps_split(gps_data->latitude, &lat);
+		ao_gps_split(gps_data->longitude, &lon);
 		printf(" %2d:%02d:%02d %2d°%02d.%04d'%c %2d°%02d.%04d'%c %5dm\n",
 		       gps_data->hour,
 		       gps_data->minute,
 		       gps_data->second,
-		       gps_data->latitude.degrees,
-		       gps_data->latitude.minutes,
-		       gps_data->latitude.minutes_fraction,
-		       (gps_data->flags & AO_GPS_LATITUDE_MASK) == AO_GPS_LATITUDE_NORTH ?
-		       'N' : 'S',
-		       gps_data->longitude.degrees,
-		       gps_data->longitude.minutes,
-		       gps_data->longitude.minutes_fraction,
-		       (gps_data->flags & AO_GPS_LONGITUDE_MASK) == AO_GPS_LONGITUDE_WEST ?
-		       'W' : 'E',
+		       lat.degrees,
+		       lat.minutes,
+		       lat.minutes_fraction,
+		       lat.positive ? 'N' : 'S',
+		       lon.degrees,
+		       lon.minutes,
+		       lon.minutes_fraction,
+		       lon.positive ? 'E' : 'W',
 		       gps_data->altitude,
 		       (gps_data->flags & AO_GPS_NUM_SAT_MASK) >> AO_GPS_NUM_SAT_SHIFT);
 	} else {