From a3e4a250bd51d36a479c735e87e009a47a2f9fb5 Mon Sep 17 00:00:00 2001
From: Jonathan Naylor <naylorjs@yahoo.com>
Date: Sun, 14 Mar 2021 21:00:47 +0000
Subject: [PATCH] Make the Null Controller respond properly.

---
 NullController.cpp | 143 ++++++++++++++++++++++++++++++++++++++++++++-
 NullController.h   |   7 +++
 2 files changed, 147 insertions(+), 3 deletions(-)

diff --git a/NullController.cpp b/NullController.cpp
index fb48a04..edfeffe 100644
--- a/NullController.cpp
+++ b/NullController.cpp
@@ -18,7 +18,31 @@
 
 #include "NullController.h"
 
-CNullController::CNullController()
+#include <cstdio>
+#include <cassert>
+
+const unsigned char MMDVM_FRAME_START = 0xE0U;
+
+const unsigned char MMDVM_GET_VERSION = 0x00U;
+const unsigned char MMDVM_GET_STATUS  = 0x01U;
+const unsigned char MMDVM_SET_CONFIG  = 0x02U;
+const unsigned char MMDVM_SET_MODE    = 0x03U;
+const unsigned char MMDVM_SET_FREQ    = 0x04U;
+
+const unsigned char MMDVM_FM_PARAMS1 = 0x60U;
+const unsigned char MMDVM_FM_PARAMS2 = 0x61U;
+const unsigned char MMDVM_FM_PARAMS3 = 0x62U;
+const unsigned char MMDVM_FM_PARAMS4 = 0x63U;
+
+const unsigned char MMDVM_ACK = 0x70U;
+const unsigned char MMDVM_NAK = 0x7FU;
+
+const unsigned char PROTOCOL_VERSION = 2U; 
+
+const char* HARDWARE = "Null Modem Controller";
+
+CNullController::CNullController() :
+m_buffer(200U, "Null Controller Buffer")
 {
 }
 
@@ -33,15 +57,128 @@ bool CNullController::open()
 
 int CNullController::read(unsigned char* buffer, unsigned int length)
 {
-	return 0;
+	unsigned int dataSize = m_buffer.dataSize();
+	if (dataSize == 0U)
+		return 0;
+
+	if (length > dataSize)
+		length = dataSize;
+
+	m_buffer.getData(buffer, length);
+
+	return int(length);
 }
 
 int CNullController::write(const unsigned char* buffer, unsigned int length)
 {
-	return length;
+	switch (buffer[2U]) {
+	case MMDVM_GET_VERSION:
+		writeVersion();
+		break;
+	case MMDVM_GET_STATUS:
+		writeStatus();
+		break;
+	case MMDVM_SET_CONFIG:
+	case MMDVM_SET_FREQ:
+	case MMDVM_SET_MODE:
+	case MMDVM_FM_PARAMS1:
+	case MMDVM_FM_PARAMS2:
+	case MMDVM_FM_PARAMS3:
+	case MMDVM_FM_PARAMS4:
+		writeAck(buffer[2U]);
+		break;
+	default:
+		break;
+	}
+
+	return int(length);
 }
 
 
 void CNullController::close()
 {
 }
+
+void CNullController::writeVersion()
+{
+	unsigned char reply[200U];
+
+	reply[0U] = MMDVM_FRAME_START;
+	reply[1U] = 0U;
+	reply[2U] = MMDVM_GET_VERSION;
+
+	reply[3U] = PROTOCOL_VERSION;
+
+	// Return two bytes of mode capabilities
+	reply[4U] = 0xFFU;
+	reply[5U] = 0xFFU;
+
+	// CPU type/manufacturer. 0=Atmel ARM, 1=NXP ARM, 2=St-Micro ARM
+	reply[6U] = 2U;
+
+	// Reserve 16 bytes for the UDID
+	::memset(reply + 7U, 0x00U, 16U);
+
+	uint8_t count = 23U;
+	for (uint8_t i = 0U; HARDWARE[i] != 0x00U; i++, count++)
+		reply[count] = HARDWARE[i];
+
+	reply[1U] = count;
+
+	m_buffer.addData(reply, count);
+}
+
+void CNullController::writeStatus()
+{
+	unsigned char reply[30U];
+
+	// Send all sorts of interesting internal values
+	reply[0U] = MMDVM_FRAME_START;
+	reply[1U] = 20U;
+	reply[2U] = MMDVM_GET_STATUS;
+
+	reply[3U] = 0U;
+
+	reply[4U] = 0x00U;
+
+	reply[5U] = 0x00U;
+
+	reply[6U] = 20U;
+
+	reply[7U] = 20U;
+	reply[8U] = 20U;
+
+	reply[9U] = 20U;
+
+	reply[10U] = 20U;
+
+	reply[11U] = 20U;
+
+	reply[12U] = 20U;
+
+	reply[13U] = 20U;
+
+	reply[14U] = 0x00U;
+	reply[15U] = 0x00U;
+
+	reply[16U] = 20U;
+
+	reply[17U] = 20U;
+
+	reply[18U] = 0x00U;
+	reply[19U] = 0x00U;
+
+	m_buffer.addData(reply, 20U);
+}
+
+void CNullController::writeAck(unsigned char type)
+{
+	unsigned char reply[4U];
+
+	reply[0U] = MMDVM_FRAME_START;
+	reply[1U] = 4U;
+	reply[2U] = MMDVM_ACK;
+	reply[3U] = type;
+
+	m_buffer.addData(reply, 4U);
+}
diff --git a/NullController.h b/NullController.h
index bbf0681..2dad99b 100644
--- a/NullController.h
+++ b/NullController.h
@@ -21,6 +21,8 @@
 
 #include "ModemPort.h"
 
+#include "RingBuffer.h"
+
 class CNullController : public IModemPort {
 public:
 	CNullController();
@@ -35,6 +37,11 @@ public:
 	virtual void close();
 
 private:
+	CRingBuffer<unsigned char> m_buffer;
+
+	void writeVersion();
+	void writeStatus();
+	void writeAck(unsigned char type);
 };
 
 #endif