Add support for NMEA HDT (Heading True) sentence

README.md

@@ -26,6 +26,7 @@ systems.
 * ``GSA`` (DOP and active satellites)
 * ``GST`` (Pseudorange Noise Statistics)
 * ``GSV`` (Satellites in view)
+* ``HDT`` (Heading, True)
 * ``RMC`` (Recommended Minimum: position, velocity, time)
 * ``VTG`` (Track made good and Ground speed)
 * ``ZDA`` (Time & Date - UTC, day, month, year and local time zone)

minmea.c

@@ -365,6 +365,7 @@ struct sentence_id_map_entry sentence_id_map[] = {
     { "RMC", MINMEA_SENTENCE_RMC },
     { "VTG", MINMEA_SENTENCE_VTG },
     { "ZDA", MINMEA_SENTENCE_ZDA },
+    { "HDT", MINMEA_SENTENCE_HDT }, 
 };
 
 const char* minmea_sentence(enum minmea_sentence_id id) {
@@ -640,6 +641,21 @@ bool minmea_parse_zda(struct minmea_sentence_zda *frame, const char *sentence)
   return true;
 }
 
+bool minmea_parse_hdt(struct minmea_sentence_hdt *frame, const char *sentence)
+{    /* Scan using 't' for the union type payload pointer, 'f' for float, 'c' for char */
+    if (!minmea_scan(sentence, "tfc",
+        &frame->type,
+        &frame->heading,
+        &frame->true_heading)
+    ) return false;
+
+    /* Verify if the extracted token matches the specific HDT layout code */
+    if (memcmp(frame->type.sentence_id, "HDT", sizeof(frame->type.sentence_id)))
+            return false;    
+    return true;
+
+}
+
 int minmea_getdatetime(struct tm *tm, const struct minmea_date *date, const struct minmea_time *time_)
 {
     if (date->year == -1 || time_->hours == -1)

minmea.h

@@ -38,6 +38,7 @@ enum minmea_sentence_id {
     MINMEA_SENTENCE_RMC,
     MINMEA_SENTENCE_VTG,
     MINMEA_SENTENCE_ZDA,
+    MINMEA_SENTENCE_HDT,
 };
 
 struct minmea_float {
@@ -196,6 +197,12 @@ struct minmea_sentence_zda {
     int minute_offset;
 };
 
+struct minmea_sentence_hdt {
+    union minmea_type type;
+    struct minmea_float heading;
+    char true_heading;
+};
+
 /**
  * Calculate raw sentence checksum. Does not check sentence integrity.
  */
@@ -249,6 +256,7 @@ bool minmea_parse_gst(struct minmea_sentence_gst *frame, const char *sentence);
 bool minmea_parse_gsv(struct minmea_sentence_gsv *frame, const char *sentence);
 bool minmea_parse_vtg(struct minmea_sentence_vtg *frame, const char *sentence);
 bool minmea_parse_zda(struct minmea_sentence_zda *frame, const char *sentence);
+bool minmea_parse_hdt(struct minmea_sentence_hdt *frame, const char *sentence);
 
 /**
  * Convert GPS UTC date/time representation to a UNIX calendar time.
@@ -311,10 +319,6 @@ static inline bool minmea_isfield(char c) {
     return isprint((unsigned char) c) && c != ',' && c != '*';
 }
 
-#ifdef __cplusplus
-}
-#endif
-
 #endif /* MINMEA_H */
 
 /* vim: set ts=4 sw=4 et: */

tests.c

@@ -49,6 +49,7 @@ static const char *valid_sentences_checksum[] = {
     "$GPGST,024603.00,3.2,6.6,4.7,47.3,5.8,5.6,22.0*58",
     "$GPZDA,160012.71,11,03,2004,-1,00*7D",
     "$GNGBS,170556.00,3.0,2.9,8.3,,,,*5C",
+    "$HEHDT,234.56,T*19",
     NULL,
 };
 
@@ -64,6 +65,7 @@ static const char *invalid_sentences[] = {
     "$GPTXT,hello\n ",
     "$GPTXT,hello\r*24",
     "$GPTXT,hello\r\n$",
+    "$HEHDT,234.56,T*1E",
     NULL,
 };
 
@@ -902,7 +904,7 @@ START_TEST(test_minmea_parse_gsv6)
     const char *sentence = "$GPGSV,3,1,11,09,57,333,29.0,07,54,227,,04,49,043,24.5,03,43,129,,1*67";
     struct minmea_sentence_gsv frame = {};
     static const struct minmea_sentence_gsv expected = {
-        .type = {"GP", "GSV"},
+        .type = { .talker_id = "GP", .sentence_id = "GSV", .null_terminator = '\0' },
         .total_msgs = 3,
         .msg_nr = 1,
         .total_sats = 11,
@@ -1029,6 +1031,25 @@ START_TEST(test_minmea_parse_zda1)
 }
 END_TEST
 
+START_TEST(test_minmea_parse_hdt)
+{
+    /* Standard gyrocompass heading sentence for validation */
+    const char *hdt_sentence = "$HEHDT,234.56,T*19\r\n";
+    struct minmea_sentence_hdt frame;
+
+    /* Verify sentence ID mapping */
+    ck_assert_int_eq(minmea_sentence_id(hdt_sentence, false), MINMEA_SENTENCE_HDT);
+
+    /* Verify parser execution state */
+    ck_assert(minmea_parse_hdt(&frame, hdt_sentence) == true);
+
+    /* Verify mapped data indicators and structures */
+    ck_assert_int_eq(frame.true_heading, 'T');
+    ck_assert_int_eq(frame.heading.value, 23456);
+    ck_assert_int_eq(frame.heading.scale, 100);
+}
+END_TEST
+
 START_TEST(test_minmea_usage1)
 {
     const char *sentences[] = {
@@ -1252,6 +1273,7 @@ static Suite *minmea_suite(void)
     tcase_add_test(tc_parse, test_minmea_parse_vtg2);
     tcase_add_test(tc_parse, test_minmea_parse_vtg3);
     tcase_add_test(tc_parse, test_minmea_parse_zda1);
+    tcase_add_test(tc_parse, test_minmea_parse_hdt);
     suite_add_tcase(s, tc_parse);
 
     TCase *tc_usage = tcase_create("minmea_usage");