Add CRC calculation for IL2P

Author: leventelist

src/audio.h

@@ -208,6 +208,7 @@ struct audio_s {
 	    int il2p_max_fec;		// 1 for max FEC length, 0 for automatic based on size.
 
 	    int il2p_invert_polarity;	// 1 means invert on transmit.  Receive handles either automatically.
+        enum il2p_use_crc_t { IL2P_NOCRC = 0, IL2P_USECRC } il2p_use_crc;
 
 	    enum v26_e { V26_UNSPECIFIED=0, V26_A, V26_B } v26_alternative;
 

src/config.c

@@ -791,6 +791,7 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	  p_audio_config->achan[channel].layer2_xmit = LAYER2_AX25;
 	  p_audio_config->achan[channel].il2p_max_fec = 1;
 	  p_audio_config->achan[channel].il2p_invert_polarity = 0;
+	  p_audio_config->achan[channel].il2p_use_crc = IL2P_USECRC;
 
 	  p_audio_config->achan[channel].fix_bits = DEFAULT_FIX_BITS;
 	  p_audio_config->achan[channel].sanity_test = SANITY_APRS;
@@ -2625,13 +2626,15 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	  }
 
 /*
- * IL2PTX  [ + - ] [ 0 1 ]	- Enable IL2P transmission.  Default off.
+ * IL2PTX  [ + - ] [ 0 1 ] [ C ]	- Enable IL2P transmission.  Default off.
  *				"+" means normal polarity. Redundant since it is the default.
  *					(command line -I for first channel)
  *				"-" means inverted polarity. Do not use for 1200 bps.
  *					(command line -i for first channel)
  *				"0" means weak FEC.  Not recommended.
  *				"1" means stronger FEC.  "Max FEC."  Default if not specified.
+ *				"C" means check CRC.  Default is not to check CRC.
+ *                  Note, that it'll always generate CRC for the frame.
  */
 
 	  else if (strcasecmp(t, "IL2PTX") == 0) {
@@ -2644,6 +2647,7 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	    p_audio_config->achan[channel].layer2_xmit = LAYER2_IL2P;
 	    p_audio_config->achan[channel].il2p_max_fec = 1;
 	    p_audio_config->achan[channel].il2p_invert_polarity = 0;
+		p_audio_config->achan[channel].il2p_use_crc = IL2P_NOCRC; // Default is no CRC.
 
 	    while ((t = split(NULL,0)) != NULL) {
 	      for (char *c = t; *c != '\0'; c++) {
@@ -2659,6 +2663,11 @@ void config_init (char *fname, struct audio_s *p_audio_config,
 	            break;
 	          case '1':
 	            p_audio_config->achan[channel].il2p_max_fec = 1;
+	            break;
+			  case 'C':
+			  case 'c':
+	            p_audio_config->achan[channel].il2p_use_crc = IL2P_USECRC;
+				dw_printf ("Line %d: IL2P transmission will use CRC.\n", line);
 	            break;
 	          default:
 	            text_color_set(DW_COLOR_ERROR);

src/hdlc_rec.c

@@ -504,7 +504,7 @@ void hdlc_rec_bit_new (int chan, int subchan, int slice, int raw, int is_scrambl
 
 	if (g_audio_p->achan[chan].modem_type != MODEM_AIS) {
 	  fx25_rec_bit (chan, subchan, slice, dbit);
-	  il2p_rec_bit (chan, subchan, slice, raw);	// Note: skip NRZI.
+	  il2p_rec_bit (chan, subchan, slice, raw, g_audio_p->achan[chan].il2p_use_crc);	// Note: skip NRZI.
 	}
 
 /*

src/il2p.h

@@ -19,6 +19,7 @@
 
 #define IL2P_MAX_PACKET_SIZE (IL2P_SYNC_WORD_SIZE + IL2P_HEADER_SIZE + IL2P_HEADER_PARITY + IL2P_MAX_ENCODED_PAYLOAD_SIZE)
 
+#define IL2P_CODED_CRC_LENGTH 4
 
 ///////////////////////////////////////////////////////////////////////////////
 //
@@ -52,7 +53,7 @@ extern void il2p_set_debug(int debug);
 
 // Receives a bit stream from demodulator.
 
-extern void il2p_rec_bit (int chan, int subchan, int slice, int dbit);
+extern void il2p_rec_bit (int chan, int subchan, int slice, int dbit, int use_crc);
 
 
 
@@ -81,9 +82,9 @@ int il2p_send_frame (int chan, packet_t pp, int max_fec, int polarity);
 
 extern int il2p_encode_frame (packet_t pp, int max_fec, unsigned char *iout);
 
-packet_t il2p_decode_frame (unsigned char *irec);
+packet_t il2p_decode_frame (unsigned char *irec, int use_crc);
 
-packet_t il2p_decode_header_payload (unsigned char* uhdr, unsigned char *epayload, int *symbols_corrected);
+packet_t il2p_decode_header_payload (unsigned char* uhdr, unsigned char *epayload, int *symbols_corrected, int use_crc);
 
 
 
@@ -138,7 +139,7 @@ extern int il2p_payload_compute (il2p_payload_properties_t *p, int payload_size,
 
 extern int il2p_encode_payload (unsigned char *payload, int payload_size, int max_fec, unsigned char *enc);
 
-extern int il2p_decode_payload (unsigned char *received, int payload_size, int max_fec, unsigned char *payload_out, int *symbols_corrected);
+extern int il2p_decode_payload (unsigned char *received, int payload_size, int max_fec, unsigned char *payload_out, int *symbols_corrected, unsigned char **next_hdr);
 
 extern int il2p_get_header_attributes (unsigned char *hdr, int *hdr_type, int *max_fec);