altos: Re-send previous GPS position in APRS if lock is lost

APRS radios often show only the last received APRS packet, which means
that erasing the last known GPS position when we lose lock by sending
0/0/0 is unhelpful. Instead, just send the last known position, and
make sure that we send 0/0/0 before we're locked the first time.

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

diff --git a/src/drivers/ao_aprs.c b/src/drivers/ao_aprs.c
index c327c89702e8fc8a34c772a4752830a0c39a8d9f..d472af4eb336fa7669d06cd58a1c252c775bf4ca 100644 (file)
--- a/src/drivers/ao_aprs.c
+++ b/src/drivers/ao_aprs.c
@@ -531,9 +531,10 @@ static int tncComment(uint8_t *buf)
  */
 static int tncPositionPacket(void)
 {
-    int32_t    latitude = 0;
-    int32_t    longitude = 0;
-    int32_t    altitude = 0;
+    static int32_t     latitude;
+    static int32_t     longitude;
+    static int32_t     altitude;
+    int32_t            lat, lon, alt;
     uint8_t    *buf;
 
     if (ao_gps_data.flags & AO_GPS_VALID) {
@@ -544,30 +545,29 @@ static int tncPositionPacket(void)
            altitude = 0;
     }
 
-    altitude = (altitude * (int32_t) 10000 + (3048/2)) / (int32_t) 3048;
-    
     buf = tncBuffer;
     *buf++ = '!';
 
     /* Symbol table ID */
     *buf++ = '/';
 
-    latitude = ((uint64_t) 380926 * (900000000 - latitude)) / 10000000;
-    longitude = ((uint64_t) 190463 * (1800000000 + longitude)) / 10000000;
+    lat = ((uint64_t) 380926 * (900000000 - latitude)) / 10000000;
+    lon = ((uint64_t) 190463 * (1800000000 + longitude)) / 10000000;
 
 #define ALTITUDE_LOG_BASE      0.001998002662673f      /* log(1.002) */
 
-    altitude = logf((float) altitude) * (1/ALTITUDE_LOG_BASE);
+    alt = (altitude * (int32_t) 10000 + (3048/2)) / (int32_t) 3048;
+    alt = logf((float) altitude) * (1/ALTITUDE_LOG_BASE);
 
-    tncCompressInt(buf, latitude, 4);
+    tncCompressInt(buf, lat, 4);
     buf += 4;
-    tncCompressInt(buf, longitude, 4);
+    tncCompressInt(buf, lon, 4);
     buf += 4;
 
     /* Symbol code */
     *buf++ = '\'';
 
-    tncCompressInt(buf, altitude, 2);
+    tncCompressInt(buf, alt, 2);
     buf += 2;
 
     *buf++ = 33 + ((1 << 5) | (2 << 3));