+static void
+ao_nmea_gga()
+{
+ uint8_t i;
+
+ /* Now read the data into the gps data record
+ *
+ * $GPGGA,025149.000,4528.1723,N,12244.2480,W,1,05,2.0,103.5,M,-19.5,M,,0000*66
+ *
+ * Essential fix data
+ *
+ * 025149.000 time (02:51:49.000 GMT)
+ * 4528.1723,N Latitude 45°28.1723' N
+ * 12244.2480,W Longitude 122°44.2480' W
+ * 1 Fix quality:
+ * 0 = invalid
+ * 1 = GPS fix (SPS)
+ * 2 = DGPS fix
+ * 3 = PPS fix
+ * 4 = Real Time Kinematic
+ * 5 = Float RTK
+ * 6 = estimated (dead reckoning)
+ * 7 = Manual input mode
+ * 8 = Simulation mode
+ * 05 Number of satellites (5)
+ * 2.0 Horizontal dilution
+ * 103.5,M Altitude, 103.5M above msl
+ * -19.5,M Height of geoid above WGS84 ellipsoid
+ * ? time in seconds since last DGPS update
+ * 0000 DGPS station ID
+ * *66 checksum
+ */
+
+ ao_gps_next_tick = ao_time();
+ ao_gps_next.flags = AO_GPS_RUNNING | ao_gps_date_flags;
+ ao_gps_next.hour = ao_gps_decimal(2);
+ ao_gps_next.minute = ao_gps_decimal(2);
+ ao_gps_next.second = ao_gps_decimal(2);
+ ao_gps_skip_field(); /* skip seconds fraction */
+
+ ao_gps_next.latitude = ao_gps_parse_pos(2);
+ if (ao_gps_parse_flag('N', 'S'))
+ ao_gps_next.latitude = -ao_gps_next.latitude;
+ ao_gps_next.longitude = ao_gps_parse_pos(3);
+ if (ao_gps_parse_flag('E', 'W'))
+ ao_gps_next.longitude = -ao_gps_next.longitude;
+
+ i = ao_gps_decimal(0xff);
+ if (i == 1)
+ ao_gps_next.flags |= AO_GPS_VALID;
+
+ i = ao_gps_decimal(0xff) << AO_GPS_NUM_SAT_SHIFT;
+ if (i > AO_GPS_NUM_SAT_MASK)
+ i = AO_GPS_NUM_SAT_MASK;
+ ao_gps_next.flags |= i;
+
+ ao_gps_lexchar();
+ ao_gps_next.hdop = ao_gps_decimal(0xff);
+ if (ao_gps_next.hdop <= 50) {
+ ao_gps_next.hdop = (uint8_t) 5 * ao_gps_next.hdop;
+ if (ao_gps_char == '.')
+ ao_gps_next.hdop = (ao_gps_next.hdop +
+ ((uint8_t) ao_gps_decimal(1) >> 1));
+ } else
+ ao_gps_next.hdop = 255;
+ ao_gps_skip_field();
+
+ ao_gps_next.altitude = ao_gps_decimal(0xff);
+ ao_gps_skip_field(); /* skip any fractional portion */
+
+ /* Skip remaining fields */
+ while (ao_gps_char != '*' && ao_gps_char != '\n' && ao_gps_char != '\r') {
+ ao_gps_lexchar();
+ ao_gps_skip_field();
+ }
+ if (ao_gps_char == '*') {
+ uint8_t cksum = ao_gps_cksum ^ '*';
+ if (cksum != ao_gps_hex(2))
+ ao_gps_error = 1;
+ } else
+ ao_gps_error = 1;
+ if (!ao_gps_error) {
+ ao_mutex_get(&ao_gps_mutex);
+ ao_gps_tick = ao_gps_next_tick;
+ memcpy(&ao_gps_data, &ao_gps_next, sizeof (struct ao_gps_data));
+ ao_mutex_put(&ao_gps_mutex);
+ ao_wakeup(&ao_gps_data);
+ }
+}
+
+static void
+ao_nmea_gsv(void)
+{
+ char c;
+ uint8_t i;
+ uint8_t done;
+ /* Now read the data into the GPS tracking data record
+ *
+ * $GPGSV,3,1,12,05,54,069,45,12,44,061,44,21,07,184,46,22,78,289,47*72<CR><LF>
+ *
+ * Satellites in view data
+ *
+ * 3 Total number of GSV messages
+ * 1 Sequence number of current GSV message
+ * 12 Total sats in view (0-12)
+ * 05 SVID
+ * 54 Elevation
+ * 069 Azimuth
+ * 45 C/N0 in dB
+ * ... other SVIDs
+ * 72 checksum
+ */
+ c = ao_gps_decimal(1); /* total messages */
+ i = ao_gps_decimal(1); /* message sequence */
+ if (i == 1) {
+ ao_gps_tracking_next.channels = 0;
+ }
+ done = (uint8_t) c == i;
+ ao_gps_lexchar();
+ ao_gps_skip_field(); /* sats in view */
+ while (ao_gps_char != '*' && ao_gps_char != '\n' && ao_gps_char != '\r') {
+ i = ao_gps_tracking_next.channels;
+ c = ao_gps_decimal(2); /* SVID */
+ if (i < AO_MAX_GPS_TRACKING)
+ ao_gps_tracking_next.sats[i].svid = c;
+ ao_gps_lexchar();
+ ao_gps_skip_field(); /* elevation */
+ ao_gps_lexchar();
+ ao_gps_skip_field(); /* azimuth */
+ c = ao_gps_decimal(2); /* C/N0 */
+ if (i < AO_MAX_GPS_TRACKING) {
+ if (!(ao_gps_tracking_next.sats[i].c_n_1 = c))
+ ao_gps_tracking_next.sats[i].svid = 0;
+ ao_gps_tracking_next.channels = i + 1;
+ }
+ }
+ if (ao_gps_char == '*') {
+ uint8_t cksum = ao_gps_cksum ^ '*';
+ if (cksum != ao_gps_hex(2))
+ ao_gps_error = 1;
+ }
+ else
+ ao_gps_error = 1;
+ if (ao_gps_error)
+ ao_gps_tracking_next.channels = 0;
+ else if (done) {
+ ao_mutex_get(&ao_gps_mutex);
+ memcpy(&ao_gps_tracking_data, &ao_gps_tracking_next,
+ sizeof(ao_gps_tracking_data));
+ ao_mutex_put(&ao_gps_mutex);
+ ao_wakeup(&ao_gps_tracking_data);
+ }
+}
+
+static void
+ao_nmea_rmc(void)
+{
+ char a, c;
+ uint8_t i;
+ /* Parse the RMC record to read out the current date */
+
+ /* $GPRMC,111636.932,A,2447.0949,N,12100.5223,E,000.0,000.0,030407,,,A*61
+ *
+ * Recommended Minimum Specific GNSS Data
+ *
+ * 111636.932 UTC time 11:16:36.932
+ * A Data Valid (V = receiver warning)
+ * 2447.0949 Latitude
+ * N North/south indicator
+ * 12100.5223 Longitude
+ * E East/west indicator
+ * 000.0 Speed over ground
+ * 000.0 Course over ground
+ * 030407 UTC date (ddmmyy format)
+ * A Mode indicator:
+ * N = data not valid
+ * A = autonomous mode
+ * D = differential mode
+ * E = estimated (dead reckoning) mode
+ * M = manual input mode
+ * S = simulator mode
+ * 61 checksum
+ */
+ ao_gps_skip_field();
+ for (i = 0; i < 8; i++) {
+ ao_gps_lexchar();
+ ao_gps_skip_field();
+ }
+ a = ao_gps_decimal(2);
+ c = ao_gps_decimal(2);
+ i = ao_gps_decimal(2);
+ /* Skip remaining fields */
+ while (ao_gps_char != '*' && ao_gps_char != '\n' && ao_gps_char != '\r') {
+ ao_gps_lexchar();
+ ao_gps_skip_field();
+ }
+ if (ao_gps_char == '*') {
+ uint8_t cksum = ao_gps_cksum ^ '*';
+ if (cksum != ao_gps_hex(2))
+ ao_gps_error = 1;
+ } else
+ ao_gps_error = 1;
+ if (!ao_gps_error) {
+ ao_gps_next.year = i;
+ ao_gps_next.month = c;
+ ao_gps_next.day = a;
+ ao_gps_date_flags = AO_GPS_DATE_VALID;
+ }
+}