Decode/emit emergency/priority status

dump1090.h

@@ -215,6 +215,18 @@ typedef enum {
     NAV_MODE_TCAS = 32
 } nav_modes_t;
 
+// Matches encoding of the ES type 28/1 emergency/priority status subfield
+typedef enum {
+    EMERGENCY_NONE = 0,
+    EMERGENCY_GENERAL = 1,
+    EMERGENCY_LIFEGUARD = 2,
+    EMERGENCY_MINFUEL = 3,
+    EMERGENCY_NORDO = 4,
+    EMERGENCY_UNLAWFUL = 5,
+    EMERGENCY_DOWNED = 6,
+    EMERGENCY_RESERVED = 7
+} emergency_t;
+
 #define MODES_NON_ICAO_ADDRESS       (1<<24) // Set on addresses to indicate they are not ICAO addresses
 
 #define MODES_DEBUG_DEMOD (1<<0)
@@ -450,6 +462,7 @@ struct modesMessage {
     unsigned spi : 1;
     unsigned alert_valid : 1;
     unsigned alert : 1;
+    unsigned emergency_valid : 1;
 
     unsigned metype; // DF17/18 ME type
     unsigned mesub;  // DF17/18 ME subtype
@@ -486,6 +499,7 @@ struct modesMessage {
     unsigned squawk;            // 13 bits identity (Squawk), encoded as 4 hex digits
     char     callsign[9];       // 8 chars flight number, NUL-terminated
     unsigned category;          // A0 - D7 encoded as a single hex byte
+    emergency_t emergency;      // emergency/priority status
 
     // valid if cpr_valid
     cpr_type_t cpr_type;       // The encoding type used (surface, airborne, coarse TIS-B)

mode_s.c

@@ -986,7 +986,10 @@ static void decodeESAircraftStatus(struct modesMessage *mm, int check_imf)
     mm->mesub = getbits(me, 6, 8);
 
     if (mm->mesub == 1) {      // Emergency status squawk field
-        int ID13Field = getbits(me, 12, 24);
+        mm->emergency_valid = 1;
+        mm->emergency = (emergency_t) getbits(me, 9, 11);
+
+        unsigned ID13Field = getbits(me, 12, 24);
         if (ID13Field) {
             mm->squawk_valid = 1;
             mm->squawk   = decodeID13Field(ID13Field);
@@ -1130,7 +1133,9 @@ static void decodeESTargetStatus(struct modesMessage *mm, int check_imf)
         }
 
 
-        // 54-56: emergency/priority (ignored)
+        // 54-56: emergency/priority
+        mm->emergency_valid = 1;
+        mm->emergency = (emergency_t) getbits(me, 54, 56);
     } else if (mm->mesub == 1) { // Target state and status, V2
         // 8: SIL
         unsigned is_fms = getbit(me, 9);
@@ -1590,6 +1595,20 @@ static const char *sil_type_to_string(sil_type_t type)
     }
 }
 
+static const char *emergency_to_string(emergency_t emergency)
+{
+    switch (emergency) {
+    case EMERGENCY_NONE:      return "no emergency";
+    case EMERGENCY_GENERAL:   return "general emergency (7700)";
+    case EMERGENCY_LIFEGUARD: return "lifeguard / medical emergency";
+    case EMERGENCY_MINFUEL:   return "minimum fuel";
+    case EMERGENCY_NORDO:     return "no communications (7600)";
+    case EMERGENCY_UNLAWFUL:  return "unlawful interference (7500)";
+    case EMERGENCY_DOWNED:    return "downed aircraft";
+    default:                  return "reserved";
+    }
+}
+
 static void print_hex_bytes(unsigned char *data, size_t len) {
     size_t i;
     for (i = 0; i < len; ++i) {
@@ -2050,6 +2069,9 @@ void displayModesMessage(struct modesMessage *mm) {
         printf("  Nav modes:               %s\n", nav_modes_to_string(mm->nav.modes));
     }
 
+    if (mm->emergency_valid) {
+        printf("  Emergency/priority:      %s\n", emergency_to_string(mm->emergency));
+    }
 
     printf("\n");
     fflush(stdout);

net_io.c

@@ -1977,6 +1977,20 @@ static const char *airground_string(airground_t ag)
     }
 }
 
+static const char *emergency_enum_string(emergency_t emergency)
+{
+    switch (emergency) {
+    case EMERGENCY_NONE:      return "none";
+    case EMERGENCY_GENERAL:   return "general";
+    case EMERGENCY_LIFEGUARD: return "lifeguard";
+    case EMERGENCY_MINFUEL:   return "minfuel";
+    case EMERGENCY_NORDO:     return "nordo";
+    case EMERGENCY_UNLAWFUL:  return "unlawful";
+    case EMERGENCY_DOWNED:    return "downed";
+    default:                  return "reserved";
+    }
+}
+
 static void writeFATSVBanner()
 {
     char *p = prepareWrite(&Modes.fatsv_out, TSV_MAX_PACKET_SIZE);
@@ -2152,6 +2166,7 @@ static void writeFATSV()
         p = appendFATSVMeta(p, end, "nav_heading", a, &a->nav_heading_valid,   "%.1f", a->nav_heading);
         p = appendFATSVMeta(p, end, "nav_modes",   a, &a->nav_modes_valid,     "{%s}", nav_modes_string(a->nav_modes));
         p = appendFATSVMeta(p, end, "nav_qnh",     a, &a->nav_qnh_valid,       "%.1f", a->nav_qnh);
+        p = appendFATSVMeta(p, end, "emergency",   a, &a->emergency_valid,     "%s",   emergency_enum_string(a->emergency));
 
         // if we didn't get anything interesting, bail out.
         // We don't need to do anything special to unwind prepareWrite().

track.c

@@ -876,6 +876,10 @@ struct aircraft *trackUpdateFromMessage(struct modesMessage *mm)
         a->squawk = mm->squawk;
     }
 
+    if (mm->emergency_valid && accept_data(&a->emergency_valid, mm->source)) {
+        a->emergency = mm->emergency;
+    }
+
     if (mm->altitude_geom_valid && accept_data(&a->altitude_geom_valid, mm->source)) {
         a->altitude_geom = altitude_to_feet(mm->altitude_geom, mm->altitude_geom_unit);
     }

track.h

@@ -140,6 +140,9 @@ struct aircraft {
     data_validity squawk_valid;
     unsigned      squawk;         // Squawk
 
+    data_validity emergency_valid;
+    emergency_t   emergency;      // Emergency/priority status
+
     unsigned      category;       // Aircraft category A0 - D7 encoded as a single hex byte
 
     data_validity airground_valid;