From: Keith Packard <keithp@keithp.com>
Date: Mon, 10 Feb 2014 06:53:05 +0000 (-0800)
Subject: altos: Re-send previous GPS position in APRS if lock is lost
X-Git-Tag: 1.3.2~4
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=5001a0f882af53dde33fc531215944c9d727baf4;hp=864d1e2282ac1d241478cf663ee24112c9d3dc37

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 c327c897..d472af4e 100644
--- 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));