From 039c4d032e6bb3f3571cb85b262e4fb504ffcc91 Mon Sep 17 00:00:00 2001
From: Jon Beniston <jon@beniston.com>
Date: Thu, 25 Mar 2021 22:15:41 +0000
Subject: [PATCH] Add basic APRS support to ChirpChatDemod

---
 .../demodchirpchat/chirpchatdemod.cpp         | 39 +++++++++++++++++++
 plugins/feature/aprs/aprssettings.cpp         |  4 +-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/plugins/channelrx/demodchirpchat/chirpchatdemod.cpp b/plugins/channelrx/demodchirpchat/chirpchatdemod.cpp
index 51765c4e6..9c3f0c117 100644
--- a/plugins/channelrx/demodchirpchat/chirpchatdemod.cpp
+++ b/plugins/channelrx/demodchirpchat/chirpchatdemod.cpp
@@ -34,6 +34,7 @@
 #include "dsp/dspcommands.h"
 #include "device/deviceapi.h"
 #include "feature/feature.h"
+#include "util/ax25.h"
 #include "util/db.h"
 #include "maincore.h"
 
@@ -188,6 +189,44 @@ bool ChirpChatDemod::handleMessage(const Message& cmd)
                 getMessageQueueToGUI()->push(msgToGUI);
             }
 
+            // Is this an APRS packet?
+            // As per: https://github.com/oe3cjb/TTGO-T-Beam-LoRa-APRS/blob/master/lib/BG_RF95/BG_RF95.cpp
+            // There is a 3 byte header for LoRa APRS packets. Addressing follows in ASCII: srccall>dst:
+            // TODO: Should we check for valid CRC?
+            int colonIdx = m_lastMsgBytes.indexOf(':');
+            int greaterThanIdx =  m_lastMsgBytes.indexOf('>');
+            if ((m_lastMsgBytes[0] == '<') && (greaterThanIdx != -1) && (colonIdx != -1))
+            {
+                QByteArray packet;
+
+                // Extract addresses
+                const char *d = m_lastMsgBytes.data();
+                QString srcString = QString::fromLatin1(d + 3, greaterThanIdx - 3);
+                QString dstString = QString::fromLatin1(d + greaterThanIdx + 1, colonIdx - greaterThanIdx - 1);
+
+                // Convert to AX.25 format
+                packet.append(AX25Packet::encodeAddress(dstString));
+                packet.append(AX25Packet::encodeAddress(srcString, 1));
+                packet.append(3);
+                packet.append(-16); // 0xf0
+                packet.append(m_lastMsgBytes.mid(colonIdx+1));
+                packet.append((char)0); // dummy crc
+                packet.append((char)0);
+
+                // Forward to APRS and other packet features
+                MessagePipes& messagePipes = MainCore::instance()->getMessagePipes();
+                QList<MessageQueue*> *packetMessageQueues = messagePipes.getMessageQueues(this, "packets");
+                if (packetMessageQueues)
+                {
+                    QList<MessageQueue*>::iterator it = packetMessageQueues->begin();
+                    for (; it != packetMessageQueues->end(); ++it)
+                    {
+                        MainCore::MsgPacket *msg = MainCore::MsgPacket::create(this, packet, QDateTime::currentDateTime());
+                        (*it)->push(msg);
+                    }
+                }
+            }
+
             if (m_settings.m_autoNbSymbolsMax)
             {
                 ChirpChatDemodSettings settings = m_settings;
diff --git a/plugins/feature/aprs/aprssettings.cpp b/plugins/feature/aprs/aprssettings.cpp
index 368beca30..aa4d42654 100644
--- a/plugins/feature/aprs/aprssettings.cpp
+++ b/plugins/feature/aprs/aprssettings.cpp
@@ -24,11 +24,13 @@
 #include "aprssettings.h"
 
 const QStringList APRSSettings::m_pipeTypes = {
-    QStringLiteral("PacketDemod")
+    QStringLiteral("PacketDemod"),
+    QStringLiteral("ChirpChatDemod")
 };
 
 const QStringList APRSSettings::m_pipeURIs = {
     QStringLiteral("sdrangel.channel.packetdemod"),
+    QStringLiteral("sdrangel.channel.chirpchatdemod")
 };
 
 APRSSettings::APRSSettings()