Beeper implemented but has noise on the port - to fix

Core/Io/IO_Bus.cs

@@ -1,13 +1,13 @@
-using System.Diagnostics;
-using Core.Interfaces;
+using Core.Interfaces;
+using System.Diagnostics;
+using static System.Runtime.InteropServices.JavaScript.JSType;
 
 namespace Core.Io
 {
     public class IO_Bus
 {
-        public byte BorderColorIndex { get; private set; } = 7; // 7 is White
-
-        // 8 rows representing the Spectrum keyboard matrix. Default to 0xFF (unpressed).
+        public byte BorderColorIndex { get; private set; } = 7;
+        public bool BeeperState { get; private set; } = false;
         public byte[] KeyboardRows = new byte[8] { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
 
     public byte ReadPort(ushort portAddress)
@@ -42,11 +42,13 @@ namespace Core.Io
             // The ULA intercepts any write to an even port address
             if ((portAddress & 0x01) == 0)
             {
-                // The bottom 3 bits (0-2) define the border color!
+                // The bottom 3 bits (0-2) define the border color
                 BorderColorIndex = (byte)(portValue & 0x07);
 
-                // (Bits 3 and 4 handle the cassette MIC output and the internal speaker, 
-                // which we will need when we start playing audio!)
+                // Bit 4 controls the speaker
+                BeeperState = (portValue & 0x10) != 0;
+
+                // Bit 3 handles the cassette MIC output
             }
         }
     }

Desktop/BeeperDevice.cs

@@ -0,0 +1,41 @@
+using NAudio.Wave;
+using System;
+
+namespace Desktop
+{
+    public class BeeperDevice
+    {
+        private WaveOutEvent _waveOut;
+        private BufferedWaveProvider _buffer;
+
+        public BeeperDevice()
+        {
+            _waveOut = new WaveOutEvent();
+            _waveOut.DesiredLatency = 50; // 100ms latency to prevent buffer stutter
+
+            // 44.1kHz, 1 channel (Mono), Float format
+            _buffer = new BufferedWaveProvider(WaveFormat.CreateIeeeFloatWaveFormat(44100, 1));
+            _buffer.BufferDuration = TimeSpan.FromSeconds(1);
+            _buffer.DiscardOnBufferOverflow = true;
+
+            _waveOut.Init(_buffer);
+            _waveOut.Play();
+        }
+
+        public void AddSample(bool isHigh)
+        {
+            //Buffer overrun check and dump
+            if (_buffer.BufferedDuration.TotalMilliseconds > 100)
+            {
+                _buffer.ClearBuffer();
+            }
+
+            // Convert the boolean into a physical sound wave (-0.2 or +0.2)
+            float sampleValue = isHigh ? 0.2f : -0.2f;
+
+            // Convert the float to bytes and drop it in the pipe
+            byte[] bytes = BitConverter.GetBytes(sampleValue);
+            _buffer.AddSamples(bytes, 0, 4);
+        }
+    }
+}

Desktop/Desktop.csproj

@@ -8,6 +8,10 @@
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
+  <ItemGroup>
+    <PackageReference Include="NAudio" Version="2.3.0" />
+  </ItemGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\Core\Core.csproj" />
   </ItemGroup>

Desktop/Form1.cs

@@ -17,6 +17,7 @@ namespace Desktop
         private ULA _ula = null!;
         private TapManager _tapManager = null!;
         private DebuggerForm? _debugger = null;
+        private BeeperDevice _beeper = null!;
         private string _baseTitle = "";
         private bool _isRunning = false;
         private bool _isPaused = false;
@@ -41,6 +42,7 @@ namespace Desktop
                 _memoryBus = new MemoryBus();
                 _simpleIoBus = new IO_Bus();
                 _ula = new ULA(_memoryBus, _simpleIoBus);
+                _beeper = new BeeperDevice();
                 _tapManager = new TapManager();
                 _memoryBus.CrapRAMData();
                 byte[] romData = RomLoader.Load("48.rom");
@@ -70,6 +72,7 @@ namespace Desktop
                     var stopwatch = Stopwatch.StartNew();
                     var fpsStopwatch = Stopwatch.StartNew();
                     long scanlineCount = 0;
+                    long audioSampleCount = 0;
 
                     while (_isRunning)
                     {                       
@@ -90,6 +93,13 @@ namespace Desktop
                         // --- Execute Instruction ---
                         _cpu.Step();
 
+                        //Process audio at the correct time
+                        while (_cpu.TotalTStates >= (long)(audioSampleCount * 79.365))
+                        {
+                            _beeper.AddSample(_simpleIoBus.BeeperState);
+                            audioSampleCount++;
+                        }
+
                         // --- Check for End of Frame ---
                         if (_cpu.TotalTStates >= nextScanlineTarget)
                         {