From c491655edb68615ca49ec87b2ed06abec7ba9a7b Mon Sep 17 00:00:00 2001
From: "David E. Tiller" <3858971+dtiller@users.noreply.github.com>
Date: Fri, 18 Mar 2022 20:33:59 -0400
Subject: [PATCH] More framework.
---
src/CMakeLists.txt | 2 ++
src/eotd.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++
src/eotd.h | 1 +
src/hdlc_rec.c | 62 +++++++++++++++++++++++++++++++++++++++--
src/multi_modem.c | 8 ++++++
5 files changed, 140 insertions(+), 2 deletions(-)
create mode 100644 src/eotd.c
create mode 100644 src/eotd.h
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 46d3ac7..7afa21e 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -85,6 +85,7 @@ list(APPEND direwolf_SOURCES
dwgpsnmea.c
dwgpsd.c
mheard.c
+ eotd.c
)
if(LINUX)
@@ -317,6 +318,7 @@ list(APPEND atest_SOURCES
symbols.c
tt_text.c
textcolor.c
+ eotd.c
)
if(WIN32 OR CYGWIN)
diff --git a/src/eotd.c b/src/eotd.c
new file mode 100644
index 0000000..91f0110
--- /dev/null
+++ b/src/eotd.c
@@ -0,0 +1,69 @@
+
+// This file is part of Dire Wolf, an amateur radio packet TNC.
+//
+// Copyright (C) 2022 David Tiller, K4DET
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see .
+//
+
+
+/********************************************************************************
+ *
+ * File: eotd.c
+ *
+ * Purpose: Functions for processing received EOTD transmissions and
+ * converting to NMEA sentence representation.
+ *
+ * References: AIVDM/AIVDO protocol decoding by Eric S. Raymond
+ * https://gpsd.gitlab.io/gpsd/AIVDM.html
+ *
+ * Sample recording with about 100 messages. Test with "atest -B AIS xxx.wav"
+ * https://github.com/freerange/ais-on-sdr/wiki/example-data/long-beach-160-messages.wav
+ *
+ * Useful on-line decoder for AIS NMEA sentences.
+ * https://www.aggsoft.com/ais-decoder.htm
+ *
+ * Future? Add an interface to feed AIS data into aprs.fi.
+ * https://aprs.fi/page/ais_feeding
+ *
+ *******************************************************************************/
+
+#include "direwolf.h"
+
+#include
+#include
+#include
+#include
+#include
+
+#include "textcolor.h"
+#include "eotd.h"
+
+/*-------------------------------------------------------------------
+ *
+ * Convert EOTD binary block (from HDLC frame) to NMEA sentence.
+ *
+ * In: Pointer to EOTD binary block and number of bytes.
+ * Out: NMEA sentence. Provide size to avoid string overflow.
+ *
+ *--------------------------------------------------------------------*/
+
+void eotd_to_nmea (unsigned char *eotd, int eotd_len, char *nmea, int nmea_size)
+{
+ for (int i = 0; i < eotd_len; i++) {
+ char temp[32];
+ snprintf(temp, sizeof(temp), "%d=%02x ", i, eotd[i]);
+ strlcpy(nmea, temp, nmea_size);
+ }
+}
diff --git a/src/eotd.h b/src/eotd.h
new file mode 100644
index 0000000..64dba3a
--- /dev/null
+++ b/src/eotd.h
@@ -0,0 +1 @@
+void eotd_to_nmea (unsigned char *ais, int ais_len, char *nema, int nema_size);
diff --git a/src/hdlc_rec.c b/src/hdlc_rec.c
index 6db809c..85879e1 100644
--- a/src/hdlc_rec.c
+++ b/src/hdlc_rec.c
@@ -1,5 +1,5 @@
-//
-// This file is part of Dire Wolf, an amateur radio packet TNC.
+////
+//// This file is part of Dire Wolf, an amateur radio packet TNC.
//
// Copyright (C) 2011, 2012, 2013, 2014, 2015 John Langner, WB2OSZ
//
@@ -111,6 +111,10 @@ struct hdlc_state_s {
int eas_plus_found; /* "+" seen, indicating end of geographical area list. */
int eas_fields_after_plus; /* Number of "-" characters after the "+". */
+
+ uint32_t eotd_acc; /* Accumulate last recent 32 bits for EOTD. */
+
+ int eotd_gathering; /* Decoding in progress - valid frame. */
};
static struct hdlc_state_s hdlc_state[MAX_CHANS][MAX_SUBCHANS][MAX_SLICERS];
@@ -423,6 +427,8 @@ a good modem here and providing a result when it is received.
*
***********************************************************************************/
+#define PREAMBLE_AND_BARKER_CODE 0x55555712
+#define EOTD_MAX_LEN 8
static void eotd_rec_bit (int chan, int subchan, int slice, int raw, int future_use)
{
@@ -432,7 +438,59 @@ static void eotd_rec_bit (int chan, int subchan, int slice, int raw, int future_
* Different state information for each channel / subchannel / slice.
*/
H = &hdlc_state[chan][subchan][slice];
+
fprintf(stderr, "chan=%d subchan=%d slice=%d raw=%d\n", chan, subchan, slice, raw);
+ //dw_printf ("slice %d = %d\n", slice, raw);
+
+// Accumulate most recent 32 bits in MSB-first order.
+
+ H->eotd_acc <<= 1;
+ H->eotd_acc |= raw;
+
+ int done = 0;
+
+ if (!H->eotd_gathering && H->eotd_acc == PREAMBLE_AND_BARKER_CODE) {
+ dw_printf ("Barker Code Found\n");
+ H->olen = 0;
+ H->eotd_gathering = 1;
+ H->frame_len = 0;
+ }
+ else if (H->eotd_gathering) {
+ H->olen++;
+
+ /* Hack to skip 'dummy' 64th bit */
+ if (H->olen == 7 && H->frame_len == 7) {
+fprintf(stderr, "Special case!\n");
+ H->eotd_acc <<= 1;
+ H->olen++;
+ }
+
+ if (H->olen == 8) {
+ H->olen = 0;
+ char ch = H->eotd_acc & 0xff;
+ H->frame_buf[H->frame_len++] = ch;
+ H->frame_buf[H->frame_len] = '\0';
+ //dw_printf ("frame_buf = %s\n", H->frame_buf);
+
+ if (H->frame_len == EOTD_MAX_LEN) { // FIXME: look for other places with max length
+ done = 1;
+for (int ii=0; ii < EOTD_MAX_LEN; ii++) {fprintf(stderr, "%02x ", H->frame_buf[ii]); } fprintf(stderr, "\n");
+ }
+ }
+ }
+
+ if (done) {
+#ifdef DEBUG_E
+ dw_printf ("frame_buf %d = %s\n", slice, H->frame_buf);
+#endif
+ alevel_t alevel = demod_get_audio_level (chan, subchan);
+ multi_modem_process_rec_frame (chan, subchan, slice, H->frame_buf, H->frame_len, alevel, 0, 0);
+
+ H->eotd_acc = 0;
+ H->eotd_gathering = 0;
+ H->olen = 0;
+ H->frame_len = 0;
+ }
return;
} // end eotd_rec_bit
diff --git a/src/multi_modem.c b/src/multi_modem.c
index c59af07..86a59a7 100644
--- a/src/multi_modem.c
+++ b/src/multi_modem.c
@@ -103,6 +103,7 @@
#include "fx25.h"
#include "version.h"
#include "ais.h"
+#include "eotd.h"
@@ -342,6 +343,13 @@ void multi_modem_process_rec_frame (int chan, int subchan, int slice, unsigned c
// alevel gets in there somehow making me question why it is passed thru here.
}
+ else if (save_audio_config_p->achan[chan].modem_type == MODEM_EOTD) {
+ char nmea[300];
+ eotd_to_nmea (fbuf, flen, nmea, sizeof(nmea));
+ char monfmt[276];
+ snprintf (monfmt, sizeof(monfmt), "EOTD>%s%1d%1d:{%c%c%s", APP_TOCALL, MAJOR_VERSION, MINOR_VERSION, USER_DEF_USER_ID, USER_DEF_TYPE_AIS, nmea);
+ pp = ax25_from_text (monfmt, 1);
+ }
else {
pp = ax25_from_frame (fbuf, flen, alevel);
}