Completed support for the keyboard beeper. The Star can now beep at you.

D/Conversion.cs

@@ -45,5 +45,10 @@ public static class Conversion
         /// Conversion from microseconds to nanoseconds
         /// </summary>
         public static readonly ulong UsecToNsec = 1000;
+
+        /// <summary>
+        /// Conversion from microseconds to seconds
+        /// </summary>
+        public static readonly double UsecToSec = 0.000001;
     }
 }

D/Darkstar.csproj

@@ -122,7 +122,7 @@
     <Compile Include="Display\DisplayController.cs" />
     <Compile Include="Ethernet\HostEthernet.cs" />
     <Compile Include="Ethernet\IPacketInterface.cs" />
-    <Compile Include="IOP\Tone.cs" />
+    <Compile Include="IOP\Beeper.cs" />
     <Compile Include="Properties\Settings.Designer.cs">
       <AutoGen>True</AutoGen>
       <DesignTimeSharedInput>True</DesignTimeSharedInput>

D/IOP/Beeper.cs

@@ -0,0 +1,109 @@
+using D.Logging;
+using SDL2;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace D.IOP
+{
+    /// <summary>
+    /// Implements the tone generator used to generate simple beeps.
+    /// This is driven by an i8253 programmable interval timer.
+    /// </summary>
+    public class Beeper
+    {        
+        public Beeper()
+        {
+            Reset();
+        }
+
+        public void Reset()
+        {
+            _lsb = 0;
+            _loadLSB = true;
+            _frequency = 0.0;
+            _enabled = false;
+            _sampleOn = false;
+            _periodInSamples = 0;
+
+            _sampleBuffer = new byte[0x10000];
+        }
+
+        public void LoadPeriod(byte value)
+        {
+            if (_loadLSB)
+            {
+                _lsb = value;
+            }
+            else
+            {
+                // "The period (in usec*1.8432) will be in the range ~29..65535."
+                double period = ((value << 8) | _lsb) / 1.8432;
+
+                // The above is in usec; convert to seconds:
+                period = period * Conversion.UsecToSec;
+
+                // Invert to get the frequency in Hz:
+                _frequency = 1.0 / period;
+
+                if (Log.Enabled) Log.Write(LogComponent.Beeper, "Tone frequency set to {0}", _frequency);
+
+                // And find out the length in samples at 44.1Khz.
+                _periodInSamples = 44100.0 / _frequency;
+            }
+
+            _loadLSB = !_loadLSB;
+        }
+
+        public void EnableTone()
+        {
+            if (Log.Enabled) Log.Write(LogComponent.Beeper, "Tone enabled.", _frequency);
+            _enabled = true;
+        }
+
+        public void DisableTone()
+        {
+            if (Log.Enabled && _enabled) Log.Write(LogComponent.Beeper, "Tone disabled.", _frequency);
+            _enabled = false;
+        }
+
+        public void AudioCallback(IntPtr userData, IntPtr stream, int length)
+        {
+            if (_enabled)
+            {
+                for (int i = 0; i < length; i++)
+                {
+                    _position++;
+
+                    if (_position > _periodInSamples)
+                    {
+                        _position -= _periodInSamples;
+                        _sampleOn = !_sampleOn;
+                    }
+
+                    _sampleBuffer[i] = (byte)(_enabled ? (_sampleOn ? 0x3f : 0x00) : 0x00);
+                }
+            }
+            else
+            {
+                Array.Clear(_sampleBuffer, 0, length);
+            }
+
+            Marshal.Copy(_sampleBuffer, 0, stream, length);
+        }
+
+        private byte[] _sampleBuffer;
+
+        private bool _loadLSB;
+        private byte _lsb;
+
+        private double _frequency;
+        private bool _enabled;
+        private double _position;
+        private double _periodInSamples;
+        private bool _sampleOn;
+    }
+}

D/IOP/IOProcessor.cs

@@ -54,7 +54,7 @@ public IOProcessor(DSystem system)
             _floppyController = new FloppyController(_floppyDrive, _system);
             _dma = new DMAController(this);
             _tty = new Printer();
-            _tone = new Tone();
+            _beeper = new Beeper();
 
             //
             // Register DMA devices with controller
@@ -143,9 +143,9 @@ public Printer Printer
             get { return _tty; }
         }
 
-        public Tone Tone
+        public Beeper Beeper
         {
-            get { return _tone; }
+            get { return _beeper; }
         }
 
         private i8085 _cpu;
@@ -161,7 +161,7 @@ public Tone Tone
         private Keyboard _keyboard;
         private Mouse _mouse;
         private Printer _tty;
-        private Tone _tone;
+        private Beeper _beeper;
         private DSystem _system;
 
         //

D/IOP/MiscIO.cs

@@ -120,7 +120,7 @@ public void WritePort(int port, byte value)
                     // i8253 Timer channel #1 - used to set the Keyboard bell (tone) frequency.
                     // This is a 16-bit value loaded one byte at a time, LSB first.
                     // Send the word off to the tone generator.
-                    _iop.Tone.LoadInterval(value);
+                    _iop.Beeper.LoadPeriod(value);
                     break;
 
                 case 0x8f:
@@ -180,11 +180,11 @@ public void WritePort(int port, byte value)
 
                     if ((value & 0x20) != 0)
                     {
-                        _iop.Tone.EnableTone();
+                        _iop.Beeper.EnableTone();
                     }
                     else
                     {
-                        _iop.Tone.DisableTone();
+                        _iop.Beeper.DisableTone();
                     }
 
                     if ((value & 0x10) != 0)

D/Logging/Log.cs

@@ -82,7 +82,7 @@ public enum LogComponent
         EthernetPacket = 0x10000000,
 
         // Keyboard tone
-        Tone = 0x20000000,
+        Beeper = 0x20000000,
 
         // Configuration
         Configuration =   0x40000000,
@@ -111,9 +111,9 @@ public static class Log
     {
         static Log()
         {
-            Enabled = true;
-            _components = LogComponent.Tone | LogComponent.IOPPrinter;
-            _type = LogType.All;
+            Enabled = false;
+            _components = LogComponent.None;
+            _type = LogType.None;
             _logIndex = 0;
         }
 

D/UI/DWindow-IO.cs

@@ -974,6 +974,8 @@ private void InitializeSDL()
         {
             int retVal;
 
+            SDL.SDL_SetHint("SDL_WINDOWS_DISABLE_THREAD_NAMING", "1");
+
             // Get SDL humming
             if ((retVal = SDL.SDL_Init(SDL.SDL_INIT_EVERYTHING)) < 0)
             {
@@ -1030,25 +1032,28 @@ private void InitializeSDL()
             _renderEvent = new SDL.SDL_Event();
             _renderEvent.type = (SDL.SDL_EventType)_renderEventType;
 
-
-
+            //
+            // Initialize SDL Audio:
+            // I'd prefer to do this in the Beeper class but there's some undocumented
+            // dependency on having an active SDL window, so we do it here to keep
+            // things simple.
+            //
             SDL.SDL_AudioSpec desired = new SDL.SDL_AudioSpec();
             SDL.SDL_AudioSpec obtained = new SDL.SDL_AudioSpec();
+
+            _audioCallback = _system.IOP.Beeper.AudioCallback;
 
             desired.freq = 44100;
             desired.format = SDL.AUDIO_U8;
             desired.channels = 1;
-            desired.callback = _system.IOP.Tone.AudioCallback;
-            desired.samples = 1;
+            desired.callback = _audioCallback;
+            desired.samples = 1024;
 
             uint deviceId = SDL.SDL_OpenAudioDevice(null, 0, ref desired, out obtained, 0);
 
-
             SDL.SDL_PauseAudioDevice(deviceId, 0);
 
-            if (Log.Enabled) Log.Write(LogComponent.Tone, "SDL Audio initialized, device id {0}", deviceId);
-
-
+            if (Log.Enabled) Log.Write(LogComponent.Beeper, "SDL Audio initialized, device id {0}", deviceId);
         }
 
         private void CreateDisplayTexture(bool filter)
@@ -1206,5 +1211,13 @@ private void ToggleFullScreen(bool fullScreen)
         // Rendering textures
         private IntPtr _displayTexture = IntPtr.Zero;
         private ReaderWriterLockSlim _textureLock;
+
+        //
+        // Local reference for the SDL Audio callback:
+        // SDL-CS doesn't hold this reference which causes
+        // problems when the GC runs.  We keep this reference for as long
+        // as the Display Window is active.
+        //
+        private SDL.SDL_AudioCallback _audioCallback;
     }
 }