EAS SAME reception.

Author: wb2osz

CHANGES.md

@@ -18,7 +18,9 @@
 
 - "-X" option enables FX.25 transmission.  FX.25 reception is always enabled so you don't need to do anything special.  "What is FX.25?" you might ask.  It is forward error correction (FEC) added in a way that is completely compatible with an ordinary AX.25 frame.  See new document ***AX25\_plus\_FEC\_equals\_FX25.pdf*** for details.
 
-- Receive AIS location data from ships.  Enable by using "-B AIS" command line option or "MODEM AIS" in the configuration file.  AIS NMEA sentences are encapsulated in APRS user-defined data with a "{DA" prefix.  This uses 9600 bps so you need to use wide band audio, not what comes out of the speaker.
+- Receive AIS location data from ships.  Enable by using "-B AIS" command line option or "MODEM AIS" in the configuration file.  AIS NMEA sentences are encapsulated in APRS user-defined data with a "{DA" prefix.  This uses 9600 bps so you need to use wide band audio, not what comes out of the speaker.  There is also a "-A" option to generate APRS Object Reports.
+
+- Receive Emergency Alert System (EAS) Specific Area Message Encoding (SAME).  Enable by using "-B EAS" command line option or "MODEM EAS" in the configuration file.  EAS SAME messages are encapsulated in APRS user-defined data with a "{DE" prefix.  This uses low speed AFSK so speaker output is fine.
 
 - "-t" option now accepts more values to accommodate inconsistent handling of text color control codes by different terminal emulators.  The default, 1, should work with most modern terminal types.  If the colors are not right, try "-t 9" to see the result of the different choices and pick the best one.  If none of them look right, file a bug report and specify: operating system version (e.g. Raspbian Buster), terminal emulator type and version (e.g.  LXTerminal 0.3.2).   Include a screen capture.
 

src/atest.c

@@ -277,6 +277,9 @@ int main (int argc, char *argv[])
 	      if (strcasecmp(optarg, "AIS") == 0) {
 	        B_opt = 12345;	// See special case below.
 	      }
+	      else if (strcasecmp(optarg, "EAS") == 0) {
+	        B_opt = 23456;	// See special case below.
+	      }
 	      else {
 	        B_opt = atoi(optarg);
 	      }
@@ -464,6 +467,14 @@ int main (int argc, char *argv[])
 	  my_audio_config.achan[0].space_freq = 0;
 	  strlcpy (my_audio_config.achan[0].profiles, " ", sizeof(my_audio_config.achan[0].profiles));	// avoid getting default later.
 	}
+	else if (my_audio_config.achan[0].baud == 23456) {
+	  my_audio_config.achan[0].modem_type = MODEM_EAS;
+	  my_audio_config.achan[0].baud = 521;	// Actually 520.83 but we have an integer field here.
+						// Will make more precise in afsk demod init.
+	  my_audio_config.achan[0].mark_freq = 2083;	// Actually 2083.3 - logic 1.
+	  my_audio_config.achan[0].space_freq = 1563;	// Actually 1562.5 - logic 0.
+	  strlcpy (my_audio_config.achan[0].profiles, "D", sizeof(my_audio_config.achan[0].profiles));
+	}
 	else {
 	  my_audio_config.achan[0].modem_type = MODEM_SCRAMBLE;
 	  my_audio_config.achan[0].mark_freq = 0;
@@ -945,6 +956,7 @@ static void usage (void) {
 	dw_printf ("               4800 bps uses 8PSK based on V.27 standard.\n");
 	dw_printf ("               9600 bps and up uses K9NG/G3RUH standard.\n");
 	dw_printf ("               AIS for ship Automatic Identification System.\n");
+	dw_printf ("               EAS for Emergency Alert System (EAS) Specific Area Message Encoding (SAME).\n");
 	dw_printf ("\n");
 	dw_printf ("        -g     Use G3RUH modem rather rather than default for data rate.\n");
 	dw_printf ("        -j     2400 bps QPSK compatible with direwolf <= 1.5.\n");

src/audio.h

@@ -148,7 +148,7 @@ struct audio_s {
                                 	/* Could all be the same or different. */
 
 
-	    enum modem_t { MODEM_AFSK, MODEM_BASEBAND, MODEM_SCRAMBLE, MODEM_QPSK, MODEM_8PSK, MODEM_OFF, MODEM_16_QAM, MODEM_64_QAM, MODEM_AIS } modem_type;
+	    enum modem_t { MODEM_AFSK, MODEM_BASEBAND, MODEM_SCRAMBLE, MODEM_QPSK, MODEM_8PSK, MODEM_OFF, MODEM_16_QAM, MODEM_64_QAM, MODEM_AIS, MODEM_EAS } modem_type;
 
 					/* Usual AFSK. */
 					/* Baseband signal. Not used yet. */

src/config.c

@@ -1279,6 +1279,9 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	    if (strcasecmp(t,"AIS") == 0) {
 	      n = 12345;	// See special case later.
 	    }
+	    else if (strcasecmp(t,"EAS") == 0) {
+	      n = 23456;	// See special case later.
+	    }
 	    else {
 	      n = atoi(t);
 	    }
@@ -1328,6 +1331,14 @@ void config_init (char *fname, struct audio_s *p_audio_config,
               p_audio_config->achan[channel].mark_freq = 0;
               p_audio_config->achan[channel].space_freq = 0;
 	    }
+	    else if (p_audio_config->achan[channel].baud == 23456) {
+	      p_audio_config->achan[channel].modem_type = MODEM_EAS;
+	      p_audio_config->achan[channel].baud = 521;	// Actually 520.83 but we have an integer field here.
+								// Will make more precise in afsk demod init.
+	      p_audio_config->achan[channel].mark_freq = 2083;	// Actually 2083.3 - logic 1.
+	      p_audio_config->achan[channel].space_freq = 1563;	// Actually 1562.5 - logic 0.
+	      // ? strlcpy (p_audio_config->achan[channel].profiles, "D", sizeof(p_audio_config->achan[channel].profiles));
+	    }
 	    else {
               p_audio_config->achan[channel].modem_type = MODEM_SCRAMBLE;
               p_audio_config->achan[channel].mark_freq = 0;

src/demod.c

@@ -133,6 +133,20 @@ int demod_init (struct audio_s *pa)
 	      break;
 
 	    case MODEM_AFSK:
+	    case MODEM_EAS:
+
+	      if (save_audio_config_p->achan[chan].modem_type == MODEM_EAS) {
+		if (save_audio_config_p->achan[chan].fix_bits != RETRY_NONE) {
+	          text_color_set(DW_COLOR_INFO);
+		  dw_printf ("Channel %d: FIX_BITS option has been turned off for EAS.\n", chan);
+	          save_audio_config_p->achan[chan].fix_bits = RETRY_NONE;
+	        }
+		if (save_audio_config_p->achan[chan].passall != 0) {
+	          text_color_set(DW_COLOR_INFO);
+		  dw_printf ("Channel %d: PASSALL option has been turned off for EAS.\n", chan);
+	          save_audio_config_p->achan[chan].passall = 0;
+	        }
+	      }
 
 /*
  * Tear apart the profile and put it back together in a normalized form:
@@ -954,6 +968,7 @@ void demod_process_sample (int chan, int subchan, int sam)
 	    break;
 
 	  case MODEM_AFSK:
+	  case MODEM_EAS:
 
 	    if (save_audio_config_p->achan[chan].decimate > 1) {
 
@@ -1070,7 +1085,8 @@ alevel_t demod_get_audio_level (int chan, int subchan)
 
 	alevel.rec = (int) (( D->alevel_rec_peak - D->alevel_rec_valley ) * 50.0f + 0.5f);
 
-	if (save_audio_config_p->achan[chan].modem_type == MODEM_AFSK) {
+	if (save_audio_config_p->achan[chan].modem_type == MODEM_AFSK ||
+	    save_audio_config_p->achan[chan].modem_type == MODEM_EAS) {
 
 	  /* For AFSK, we have mark and space amplitudes. */
 

src/demod_afsk.c

@@ -307,9 +307,18 @@ void demod_afsk_init (int samples_per_sec, int baud, int mark_freq,
 /*
  * Calculate constants used for timing.
  * The audio sample rate must be at least a few times the data rate.
+ *
+ * Baud is an integer so we hack in a fine ajustment for EAS.
+ * Probably makes no difference because the DPLL keeps it in sync.
+ *
+ * A fraction if a Hz would make no difference for the filters.
  */
-
-	D->pll_step_per_sample = (int) round((TICKS_PER_PLL_CYCLE * (double)baud) / ((double)samples_per_sec));
+	if (baud == 521) {
+	  D->pll_step_per_sample = (int) round((TICKS_PER_PLL_CYCLE * (double)520.83) / ((double)samples_per_sec));
+	}
+	else {
+	  D->pll_step_per_sample = (int) round((TICKS_PER_PLL_CYCLE * (double)baud) / ((double)samples_per_sec));
+	}
 
 /*
  * Convert number of bit times to number of taps.

src/direwolf.c

@@ -288,7 +288,7 @@ int main (int argc, char *argv[])
 	text_color_init(t_opt);
 	text_color_set(DW_COLOR_INFO);
 	//dw_printf ("Dire Wolf version %d.%d (%s) Beta Test 4\n", MAJOR_VERSION, MINOR_VERSION, __DATE__);
-	dw_printf ("Dire Wolf DEVELOPMENT version %d.%d %s (%s)\n", MAJOR_VERSION, MINOR_VERSION, "F", __DATE__);
+	dw_printf ("Dire Wolf DEVELOPMENT version %d.%d %s (%s)\n", MAJOR_VERSION, MINOR_VERSION, "G", __DATE__);
 	//dw_printf ("Dire Wolf version %d.%d\n", MAJOR_VERSION, MINOR_VERSION);
 
 
@@ -435,6 +435,9 @@ int main (int argc, char *argv[])
 	    if (strcasecmp(optarg, "AIS") == 0) {
 	      B_opt = 12345;	// See special case below.
 	    }
+	    else if (strcasecmp(optarg, "EAS") == 0) {
+	      B_opt = 23456;	// See special case below.
+	    }
 	    else {
 	      B_opt = atoi(optarg);
 	    }
@@ -749,6 +752,14 @@ int main (int argc, char *argv[])
 	    audio_config.achan[0].mark_freq = 0;
 	    audio_config.achan[0].space_freq = 0;
 	  }
+	  else if (audio_config.achan[0].baud == 23456) {
+	    audio_config.achan[0].modem_type = MODEM_EAS;
+	    audio_config.achan[0].baud = 521;	// Actually 520.83 but we have an integer field here.
+						// Will make more precise in afsk demod init.
+	    audio_config.achan[0].mark_freq = 2083;	// Actually 2083.3 - logic 1.
+	    audio_config.achan[0].space_freq = 1563;	// Actually 1562.5 - logic 0.
+	    strlcpy (audio_config.achan[0].profiles, "D", sizeof(audio_config.achan[0].profiles));
+	  }
 	  else {
             audio_config.achan[0].modem_type = MODEM_SCRAMBLE;
             audio_config.achan[0].mark_freq = 0;
@@ -1451,6 +1462,7 @@ static void usage (char **argv)
 	dw_printf ("                     4800 bps uses 8PSK based on V.27 standard.\n");
 	dw_printf ("                     9600 bps and up uses K9NG/G3RUH standard.\n");
 	dw_printf ("                     AIS for ship Automatic Identification System.\n");
+	dw_printf ("                     EAS for Emergency Alert System (EAS) Specific Area Message Encoding (SAME).\n");
 	dw_printf ("    -g             Force G3RUH modem regardless of speed.\n");
 	dw_printf ("    -j             2400 bps QPSK compatible with direwolf <= 1.5.\n");
 	dw_printf ("    -J             2400 bps QPSK compatible with MFJ-2400.\n");