From 95b7d8106a9898dfa2d2752699c56787b54dbb30 Mon Sep 17 00:00:00 2001
From: Chipster <go@w.ay>
Date: Wed, 4 Nov 2026 12:31:36 -0600
Subject: [PATCH] Add a qso-info MQTT topic for modems with their own screen

A modem with its own screen, such as the DVMEGA CAST, shows who is
talking from QSO information frames (0x91). Since the display moved out
of MMDVM-Host nothing sends them, so the screen stays blank. A message
on the new qso-info topic is written to the modem as a QSO information
frame, its body as given (mode byte first), so a display program can
drive that screen. The frame is queued with the serial data, so it is
written from the modem's own thread.
---
 MMDVM-Host.cpp | 10 ++++++++++
 MMDVM-Host.h   |  1 +
 Modem.cpp      | 25 +++++++++++++++++++++++++
 Modem.h        |  1 +
 4 files changed, 37 insertions(+)

diff --git a/MMDVM-Host.cpp b/MMDVM-Host.cpp
index e23a4b11..f0684129 100644
--- a/MMDVM-Host.cpp
+++ b/MMDVM-Host.cpp
@@ -340,6 +340,7 @@ int CMMDVMHost::run()
 
 	std::vector<std::pair<std::string, void (*)(const unsigned char*, unsigned int)>> subscriptions;
 	subscriptions.push_back(std::make_pair("display-in", CMMDVMHost::onDisplay));
+	subscriptions.push_back(std::make_pair("qso-info", CMMDVMHost::onQSOInfo));
 
 	if (m_conf.getRemoteControlEnabled())
 		subscriptions.push_back(std::make_pair("command", CMMDVMHost::onCommand));
@@ -3221,3 +3222,12 @@ void CMMDVMHost::onDisplay(const unsigned char* message, unsigned int length)
 
 	host->writeSerial(message, length);
 }
+
+void CMMDVMHost::onQSOInfo(const unsigned char* message, unsigned int length)
+{
+	assert(host != nullptr);
+	assert(message != nullptr);
+
+	if (host->m_modem != nullptr)
+		host->m_modem->writeQSOInfo(message, length);
+}
diff --git a/MMDVM-Host.h b/MMDVM-Host.h
index b7bbb87c..b4382f91 100644
--- a/MMDVM-Host.h
+++ b/MMDVM-Host.h
@@ -213,6 +213,7 @@ class CMMDVMHost
 	void writeJSONMessage(const std::string& message);
 
 	static void onDisplay(const unsigned char* message, unsigned int length);
+	static void onQSOInfo(const unsigned char* message, unsigned int length);
 	static void onCommand(const unsigned char* command, unsigned int length);
 };
 
diff --git a/Modem.cpp b/Modem.cpp
index 68510da5..63fb87d3 100644
--- a/Modem.cpp
+++ b/Modem.cpp
@@ -1943,6 +1943,31 @@ bool CModem::writeSerialData(const unsigned char* data, unsigned int length)
 	return true;
 }
 
+// A QSO information frame built by the caller (mode byte first), for a
+// modem with its own screen such as the DVMega CAST. Queued with the
+// serial data so it is written from the modem's own thread.
+bool CModem::writeQSOInfo(const unsigned char* data, unsigned int length)
+{
+	assert(data != nullptr);
+
+	if (length == 0U || length > 250U)
+		return false;
+
+	unsigned char buffer[255U];
+
+	buffer[0U] = MMDVM_FRAME_START;
+	buffer[1U] = length + 3U;
+	buffer[2U] = MMDVM_QSO_INFO;
+
+	::memcpy(buffer + 3U, data, length);
+
+	unsigned char len = length + 3U;
+	m_txSerialData.addData(&len, 1U);
+	m_txSerialData.addData(buffer, len);
+
+	return true;
+}
+
 bool CModem::hasTX() const
 {
 	return m_tx;
diff --git a/Modem.h b/Modem.h
index 251b850e..0b882a84 100644
--- a/Modem.h
+++ b/Modem.h
@@ -192,6 +192,7 @@ class CModem {
 	unsigned int readTransparentData(unsigned char* data);
 
 	bool writeSerialData(const unsigned char* data, unsigned int length);
+	bool writeQSOInfo(const unsigned char* data, unsigned int length);
 	unsigned int readSerialData(unsigned char* data);
 
 	unsigned char getMode() const;