wip

src/core/core.vcxproj

@@ -148,6 +148,7 @@
     <ClCompile Include="settings.cpp" />
     <ClCompile Include="shadergen.cpp" />
     <ClCompile Include="sio.cpp" />
+    <ClCompile Include="sio_connection.cpp" />
     <ClCompile Include="spu.cpp" />
     <ClCompile Include="system.cpp" />
     <ClCompile Include="texture_replacements.cpp" />
@@ -228,6 +229,7 @@
     <ClInclude Include="shadergen.h" />
     <ClInclude Include="shader_cache_version.h" />
     <ClInclude Include="sio.h" />
+    <ClInclude Include="sio_connection.h" />
     <ClInclude Include="spu.h" />
     <ClInclude Include="system.h" />
     <ClInclude Include="texture_replacements.h" />

src/core/core.vcxproj.filters

@@ -58,6 +58,7 @@
     <ClCompile Include="texture_replacements.cpp" />
     <ClCompile Include="gdb_protocol.h" />
     <ClCompile Include="multitap.cpp" />
+    <ClCompile Include="sio_connection.cpp" />
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="types.h" />
@@ -118,5 +119,6 @@
     <ClInclude Include="texture_replacements.h" />
     <ClInclude Include="shader_cache_version.h" />
     <ClInclude Include="multitap.h" />
+    <ClInclude Include="sio_connection.h" />
   </ItemGroup>
 </Project>

src/core/host_interface.cpp

@@ -610,6 +610,7 @@ void HostInterface::SetDefaultSettings(SettingsInterface& si)
   si.SetBoolValue("Debug", "ShowTimersState", false);
   si.SetBoolValue("Debug", "ShowMDECState", false);
   si.SetBoolValue("Debug", "ShowDMAState", false);
+  si.SetBoolValue("Debug", "ShowSIOState", false);
 
   si.SetIntValue("Hacks", "DMAMaxSliceTicks", static_cast<int>(Settings::DEFAULT_DMA_MAX_SLICE_TICKS));
   si.SetIntValue("Hacks", "DMAHaltTicks", static_cast<int>(Settings::DEFAULT_DMA_HALT_TICKS));

src/core/settings.cpp

@@ -308,6 +308,7 @@ void Settings::Load(SettingsInterface& si)
   debugging.show_timers_state = si.GetBoolValue("Debug", "ShowTimersState");
   debugging.show_mdec_state = si.GetBoolValue("Debug", "ShowMDECState");
   debugging.show_dma_state = si.GetBoolValue("Debug", "ShowDMAState");
+  debugging.show_sio_state = si.GetBoolValue("Debug", "ShowSIOState");
 
   texture_replacements.enable_vram_write_replacements =
     si.GetBoolValue("TextureReplacements", "EnableVRAMWriteReplacements", false);
@@ -468,6 +469,7 @@ void Settings::Save(SettingsInterface& si) const
   si.SetBoolValue("Debug", "ShowTimersState", debugging.show_timers_state);
   si.SetBoolValue("Debug", "ShowMDECState", debugging.show_mdec_state);
   si.SetBoolValue("Debug", "ShowDMAState", debugging.show_dma_state);
+  si.SetBoolValue("Debug", "ShowSIOState", debugging.show_sio_state);
 
   si.SetBoolValue("TextureReplacements", "EnableVRAMWriteReplacements",
                   texture_replacements.enable_vram_write_replacements);

src/core/settings.h

@@ -185,6 +185,7 @@ struct Settings
     mutable bool show_timers_state = false;
     mutable bool show_mdec_state = false;
     mutable bool show_dma_state = false;
+    mutable bool show_sio_state = false;
   } debugging;
 
   // texture replacements

src/core/sio.cpp

@@ -1,12 +1,16 @@
 #include "sio.h"
 #include "common/log.h"
 #include "common/state_wrapper.h"
-#include "controller.h"
 #include "host_interface.h"
+#include "imgui.h"
 #include "interrupt_controller.h"
-#include "memory_card.h"
+#include "sio_connection.h"
+#include "system.h"
+#include "timing_event.h"
 Log_SetChannel(SIO);
 
+static constexpr std::array<u32, 4> s_mul_factors = {{1, 16, 64, 0}};
+
 SIO g_sio;
 
 SIO::SIO() = default;
@@ -15,10 +19,23 @@ SIO::~SIO() = default;
 
 void SIO::Initialize()
 {
+  m_transfer_event = TimingEvents::CreateTimingEvent(
+    "SIO Transfer", 1, 1, [](void* param, TickCount ticks, TickCount ticks_late) { g_sio.TransferEvent(); }, nullptr,
+    false);
+
+  if (true)
+    m_connection = SIOConnection::CreateSocketServer("0.0.0.0", 1337);
+    //m_connection = SIOConnection::CreateSocketClient("127.0.0.1", 1337);
+
+  m_stat.bits = 0;
   Reset();
 }
 
-void SIO::Shutdown() {}
+void SIO::Shutdown()
+{
+  m_connection.reset();
+  m_transfer_event.reset();
+}
 
 void SIO::Reset()
 {
@@ -27,41 +44,112 @@ void SIO::Reset()
 
 bool SIO::DoState(StateWrapper& sw)
 {
-  sw.Do(&m_SIO_CTRL.bits);
-  sw.Do(&m_SIO_STAT.bits);
-  sw.Do(&m_SIO_MODE.bits);
-  sw.Do(&m_SIO_BAUD);
+  const bool dtr = m_stat.DTRINPUTLEVEL;
+  const bool rts = m_stat.CTSINPUTLEVEL;
+
+  sw.Do(&m_ctrl.bits);
+  sw.Do(&m_stat.bits);
+  sw.Do(&m_mode.bits);
+  sw.Do(&m_baud_rate);
+
+  m_stat.DTRINPUTLEVEL = dtr;
+  m_stat.CTSINPUTLEVEL = rts;
 
   return !sw.HasError();
 }
 
+void SIO::SoftReset()
+{
+  m_ctrl.bits = 0;
+  m_stat.RXPARITY = false;
+  m_stat.RXFIFOOVERRUN = false;
+  m_stat.RXBADSTOPBIT = false;
+  m_stat.INTR = false;
+  m_mode.bits = 0;
+  m_baud_rate = 0xDC;
+  m_data_in.Clear();
+  m_data_out = 0;
+  m_data_out_full = false;
+
+  UpdateEvent();
+  UpdateTXRX();
+}
+
+void SIO::UpdateTXRX()
+{
+  m_stat.TXRDY = !m_data_out_full && m_ctrl.TXEN;
+  m_stat.TXDONE = !m_data_out_full;
+  m_stat.RXFIFONEMPTY = !m_data_in.IsEmpty();
+}
+
+void SIO::SetInterrupt()
+{
+  Log_DevPrintf("Set SIO IRQ");
+  m_stat.INTR = true;
+  g_interrupt_controller.InterruptRequest(InterruptController::IRQ::SIO);
+}
+
 u32 SIO::ReadRegister(u32 offset)
 {
   switch (offset)
   {
     case 0x00: // SIO_DATA
     {
-      Log_ErrorPrintf("Read SIO_DATA");
+      m_transfer_event->InvokeEarly(false);
 
-      const u8 value = 0xFF;
-      return (ZeroExtend32(value) | (ZeroExtend32(value) << 8) | (ZeroExtend32(value) << 16) |
-              (ZeroExtend32(value) << 24));
+      const u32 data_in_size = m_data_in.GetSize();
+      u32 res = 0;
+      switch (data_in_size)
+      {
+        case 8:
+        case 7:
+        case 6:
+        case 5:
+        case 4:
+          res = ZeroExtend32(m_data_in.Peek(3)) << 24;
+          [[fallthrough]];
+
+        case 3:
+          res |= ZeroExtend32(m_data_in.Peek(2)) << 16;
+          [[fallthrough]];
+
+        case 2:
+          res |= ZeroExtend32(m_data_in.Peek(1)) << 8;
+          [[fallthrough]];
+
+        case 1:
+          res |= ZeroExtend32(m_data_in.Peek(0));
+          m_data_in.RemoveOne();
+          break;
+
+        case 0:
+        default:
+          res = 0xFFFFFFFFu;
+          break;
+      }
+
+      Log_WarningPrintf("Read SIO_DATA -> 0x%08X", res);
+      UpdateTXRX();
+      return res;
     }
 
     case 0x04: // SIO_STAT
     {
-      const u32 bits = m_SIO_STAT.bits;
+      m_transfer_event->InvokeEarly(false);
+
+      const u32 bits = m_stat.bits;
+      Log_DevPrintf("Read SIO_STAT -> 0x%08X", bits);
       return bits;
     }
 
     case 0x08: // SIO_MODE
-      return ZeroExtend32(m_SIO_MODE.bits);
+      return ZeroExtend32(m_mode.bits);
 
     case 0x0A: // SIO_CTRL
-      return ZeroExtend32(m_SIO_CTRL.bits);
+      return ZeroExtend32(m_ctrl.bits);
 
     case 0x0E: // SIO_BAUD
-      return ZeroExtend32(m_SIO_BAUD);
+      return ZeroExtend32(m_baud_rate);
 
     default:
       Log_ErrorPrintf("Unknown register read: 0x%X", offset);
@@ -76,31 +164,61 @@ void SIO::WriteRegister(u32 offset, u32 value)
     case 0x00: // SIO_DATA
     {
       Log_WarningPrintf("SIO_DATA (W) <- 0x%02X", value);
+      m_transfer_event->InvokeEarly(false);
+
+      if (m_data_out_full)
+        Log_WarningPrintf("SIO TX buffer overflow, lost 0x%02X when writing 0x%02X", m_data_out, value);
+
+      m_data_out = Truncate8(value);
+      m_data_out_full = true;
+      UpdateTXRX();
       return;
     }
 
     case 0x0A: // SIO_CTRL
     {
-      Log_DebugPrintf("SIO_CTRL <- 0x%04X", value);
+      Log_DevPrintf("SIO_CTRL <- 0x%04X", value);
+      m_transfer_event->InvokeEarly(false);
 
-      m_SIO_CTRL.bits = Truncate16(value);
-      if (m_SIO_CTRL.RESET)
+      m_ctrl.bits = Truncate16(value);
+      if (m_ctrl.RESET)
         SoftReset();
 
+      if (m_ctrl.ACK)
+      {
+        m_stat.RXPARITY = false;
+        m_stat.RXFIFOOVERRUN = false;
+        m_stat.RXBADSTOPBIT = false;
+        m_stat.INTR = false;
+      }
+
+      if (!m_ctrl.RXEN)
+      {
+        Log_WarningPrintf("Clearing Input FIFO");
+        m_data_in.Clear();
+        UpdateTXRX();
+      }
+      /*if (!m_ctrl.TXEN)
+      {
+        Log_WarningPrintf("Clearing output fifo");
+        m_data_out_full = false;
+        UpdateTXRX();
+      }*/
+
       return;
     }
 
     case 0x08: // SIO_MODE
     {
-      Log_DebugPrintf("SIO_MODE <- 0x%08X", value);
-      m_SIO_MODE.bits = Truncate16(value);
+      Log_DevPrintf("SIO_MODE <- 0x%08X", value);
+      m_mode.bits = Truncate16(value);
       return;
     }
 
     case 0x0E:
     {
-      Log_DebugPrintf("SIO_BAUD <- 0x%08X", value);
-      m_SIO_BAUD = Truncate16(value);
+      Log_DevPrintf("SIO_BAUD <- 0x%08X", value);
+      m_baud_rate = Truncate16(value);
       return;
     }
 
@@ -110,12 +228,288 @@ void SIO::WriteRegister(u32 offset, u32 value)
   }
 }
 
-void SIO::SoftReset()
+void SIO::DrawDebugStateWindow()
 {
-  m_SIO_CTRL.bits = 0;
-  m_SIO_STAT.bits = 0;
-  m_SIO_STAT.TXDONE = true;
-  m_SIO_STAT.TXRDY = true;
-  m_SIO_MODE.bits = 0;
-  m_SIO_BAUD = 0xDC;
+#ifdef WITH_IMGUI
+  const float framebuffer_scale = ImGui::GetIO().DisplayFramebufferScale.x;
+
+  ImGui::SetNextWindowSize(ImVec2(600.0f * framebuffer_scale, 400.0f * framebuffer_scale), ImGuiCond_FirstUseEver);
+  if (!ImGui::Begin("SIO", nullptr))
+  {
+    ImGui::End();
+    return;
+  }
+
+  static const ImVec4 active_color{1.0f, 1.0f, 1.0f, 1.0f};
+  static const ImVec4 inactive_color{0.4f, 0.4f, 0.4f, 1.0f};
+
+  ImGui::Text("Connected: ");
+  ImGui::SameLine();
+  ImGui::TextColored((m_connection && m_connection->IsConnected()) ? active_color : inactive_color,
+                     (m_connection && m_connection->IsConnected()) ? "Yes" : "No");
+
+  ImGui::Text("Status: ");
+  ImGui::SameLine();
+
+  float pos = ImGui::GetCursorPosX();
+  ImGui::TextColored(m_stat.TXRDY ? active_color : inactive_color, "TXRDY");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.RXFIFONEMPTY ? active_color : inactive_color, "RXFIFONEMPTY");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.TXDONE ? active_color : inactive_color, "TXDONE");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.RXPARITY ? active_color : inactive_color, "RXPARITY");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.RXFIFOOVERRUN ? active_color : inactive_color, "RXFIFOOVERRUN");
+  ImGui::SetCursorPosX(pos);
+  ImGui::TextColored(m_stat.RXBADSTOPBIT ? active_color : inactive_color, "RXBADSTOPBIT");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.RXINPUTLEVEL ? active_color : inactive_color, "RXINPUTLEVEL");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.DTRINPUTLEVEL ? active_color : inactive_color, "DTRINPUTLEVEL");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.CTSINPUTLEVEL ? active_color : inactive_color, "CTSINPUTLEVEL");
+  ImGui::SameLine();
+  ImGui::TextColored(m_stat.INTR ? active_color : inactive_color, "INTR");
+
+  ImGui::NewLine();
+
+  ImGui::Text("Control: ");
+  ImGui::SameLine();
+
+  pos = ImGui::GetCursorPosX();
+  ImGui::TextColored(m_ctrl.TXEN ? active_color : inactive_color, "TXEN");
+  ImGui::SameLine();
+  ImGui::TextColored(m_ctrl.DTROUTPUT ? active_color : inactive_color, "DTROUTPUT");
+  ImGui::SameLine();
+  ImGui::TextColored(m_ctrl.RXEN ? active_color : inactive_color, "RXEN");
+  ImGui::SameLine();
+  ImGui::TextColored(m_ctrl.TXOUTPUT ? active_color : inactive_color, "TXOUTPUT");
+  ImGui::SameLine();
+  ImGui::TextColored(m_ctrl.RTSOUTPUT ? active_color : inactive_color, "RTSOUTPUT");
+  ImGui::SetCursorPosX(pos);
+  ImGui::TextColored(m_ctrl.TXINTEN ? active_color : inactive_color, "TXINTEN");
+  ImGui::SameLine();
+  ImGui::TextColored(m_ctrl.RXINTEN ? active_color : inactive_color, "RXINTEN");
+  ImGui::SameLine();
+  ImGui::TextColored(m_ctrl.RXINTEN ? active_color : inactive_color, "RXIMODE: %u", m_ctrl.RXIMODE.GetValue());
+
+  ImGui::NewLine();
+
+  ImGui::Text("Mode: ");
+  ImGui::Text("  Reload Factor: %u", s_mul_factors[m_mode.reload_factor]);
+  ImGui::Text("  Character Length: %u", m_mode.character_length.GetValue());
+  ImGui::Text("  Parity Enable: %s", m_mode.parity_enable ? "Yes" : "No");
+  ImGui::Text("  Parity Type: %u", m_mode.parity_type.GetValue());
+  ImGui::Text("  Stop Bit Length: %u", m_mode.stop_bit_length.GetValue());
+
+  ImGui::NewLine();
+
+  ImGui::Text("Baud Rate: %u", m_baud_rate);
+
+  ImGui::NewLine();
+
+  ImGui::TextColored(m_data_out_full ? active_color : inactive_color, "Output buffer: 0x%02X", m_data_out);
+
+  ImGui::Text("Input buffer: ");
+  for (u32 i = 0; i < m_data_in.GetSize(); i++)
+  {
+    ImGui::SameLine();
+    ImGui::Text("0x%02X ", m_data_in.Peek(i));
+  }
+
+  ImGui::End();
+#endif
 }
+
+TickCount SIO::GetTicksBetweenTransfers() const
+{
+  const u32 factor = s_mul_factors[m_mode.reload_factor];
+  const u32 ticks = std::max<u32>((m_baud_rate * factor) & ~u32(1), factor);
+
+  return static_cast<TickCount>(ticks);
+}
+
+void SIO::UpdateEvent()
+{
+  if (!m_connection)
+  {
+    m_transfer_event->Deactivate();
+    m_stat.CTSINPUTLEVEL = false;
+    m_stat.DTRINPUTLEVEL = false;
+    m_sync_last_cts = false;
+    m_sync_last_dtr = false;
+    m_sync_last_rts = false;
+    m_sync_remote_rts = false;
+    return;
+  }
+
+  TickCount ticks = GetTicksBetweenTransfers();
+  if (ticks == 0)
+    ticks = System::GetMaxSliceTicks();
+
+  if (m_transfer_event->GetPeriod() == ticks && m_transfer_event->IsActive())
+    return;
+
+  m_transfer_event->Deactivate();
+  m_transfer_event->SetPeriodAndSchedule(ticks);
+}
+
+void SIO::TransferEvent()
+{
+  if (m_sync_mode)
+    TransferWithSync();
+  else
+    TransferWithoutSync();
+}
+
+void SIO::TransferWithoutSync()
+{
+  // bytes aren't transmitted when CTS isn't set (i.e. there's nothing on the other side)
+  if (m_connection && m_connection->IsConnected())
+  {
+    m_stat.CTSINPUTLEVEL = true;
+    m_stat.DTRINPUTLEVEL = true;
+
+    if (m_ctrl.RXEN)
+    {
+      u8 data_in;
+      u32 data_in_size = m_connection->Read(&data_in, sizeof(data_in), 0);
+      if (data_in_size > 0)
+      {
+        if (m_data_in.IsFull())
+        {
+          Log_WarningPrintf("FIFO overrun");
+          m_data_in.RemoveOne();
+          m_stat.RXFIFOOVERRUN = true;
+        }
+
+        m_data_in.Push(data_in);
+
+        if (m_ctrl.RXINTEN)
+          SetInterrupt();
+      }
+    }
+
+    if (m_ctrl.TXEN && m_data_out_full)
+    {
+      const u8 data_out = m_data_out;
+      m_data_out_full = false;
+
+      const u32 data_sent = m_connection->Write(&data_out, sizeof(data_out));
+      if (data_sent != sizeof(data_out))
+        Log_WarningPrintf("Failed to send 0x%02X to connection", data_out);
+
+      if (m_ctrl.TXINTEN)
+        SetInterrupt();
+    }
+  }
+  else
+  {
+    m_stat.CTSINPUTLEVEL = false;
+    m_stat.DTRINPUTLEVEL = false;
+  }
+
+  UpdateTXRX();
+}
+
+void SIO::TransferWithSync()
+{
+  enum : u8
+  {
+    STATE_HAS_DATA = (1 << 0),
+    STATE_DTR_LEVEL = (1 << 1),
+    STATE_CTS_LEVEL = (1 << 2),
+    STATE_RTS_LEVEL = (1 << 3),
+  };
+
+  if (!m_connection || !m_connection->IsConnected())
+  {
+    m_stat.CTSINPUTLEVEL = false;
+    m_stat.DTRINPUTLEVEL = false;
+    m_sync_last_cts = false;
+    m_sync_last_dtr = false;
+    m_sync_last_rts = false;
+    m_sync_remote_rts = false;
+    UpdateTXRX();
+    return;
+  }
+
+  u8 buf[2] = {};
+  if (m_connection->HasData())
+  {
+    while (m_connection->Read(buf, sizeof(buf), sizeof(buf)) != 0)
+    {
+      Log_InfoPrintf("In: %02X %02X", buf[0], buf[1]);
+
+      if (buf[0] & STATE_HAS_DATA)
+      {
+        Log_WarningPrintf("Received: %02X", buf[1]);
+        if (m_data_in.IsFull())
+          m_stat.RXFIFOOVERRUN = true;
+        else
+          m_data_in.Push(buf[1]);
+
+        if (m_ctrl.RXINTEN)
+        {
+          Log_WarningPrintf("Setting RX interrupt");
+          SetInterrupt();
+        }
+      }
+
+      if (!m_stat.DTRINPUTLEVEL && buf[0] & STATE_DTR_LEVEL)
+        Log_WarningPrintf("DTR active");
+      else if (m_stat.DTRINPUTLEVEL && !(buf[0] & STATE_DTR_LEVEL))
+        Log_WarningPrintf("DTR inactive");
+      if (!m_stat.CTSINPUTLEVEL && buf[0] & STATE_CTS_LEVEL)
+        Log_WarningPrintf("CTS active");
+      else if (m_stat.CTSINPUTLEVEL && !(buf[0] & STATE_CTS_LEVEL))
+        Log_WarningPrintf("CTS inactive");
+      if (!m_sync_remote_rts && buf[0] & STATE_RTS_LEVEL)
+        Log_WarningPrintf("Remote RTS active");
+      else if (m_sync_remote_rts && !(buf[0] & STATE_RTS_LEVEL))
+        Log_WarningPrintf("Remote RTS inactive");
+
+      m_stat.DTRINPUTLEVEL = (buf[0] & STATE_DTR_LEVEL) != 0;
+      m_stat.CTSINPUTLEVEL = (buf[0] & STATE_CTS_LEVEL) != 0;
+      m_sync_remote_rts = (buf[0] & STATE_RTS_LEVEL) != 0;
+    }
+  }
+
+  const bool cts_level = m_sync_remote_rts && !m_data_in.IsFull();
+  const bool dtr_level = m_ctrl.DTROUTPUT;
+  const bool rts_level = m_ctrl.RTSOUTPUT;
+  const bool tx = (m_ctrl.TXEN || m_latched_txen) && m_stat.CTSINPUTLEVEL && m_data_out_full;
+  m_latched_txen = m_ctrl.TXEN;
+  if (cts_level != m_sync_last_cts || dtr_level != m_sync_last_dtr || rts_level != m_sync_last_rts || tx)
+  {
+    m_sync_last_cts = cts_level;
+    m_sync_last_dtr = dtr_level;
+    m_sync_last_rts = rts_level;
+
+    buf[0] = cts_level ? STATE_CTS_LEVEL : 0;
+    buf[0] |= dtr_level ? STATE_DTR_LEVEL : 0;
+    buf[0] |= rts_level ? STATE_RTS_LEVEL : 0;
+
+    buf[1] = 0;
+    if (tx)
+    {
+      Log_WarningPrintf("Sending: %02X", m_data_out);
+      buf[0] |= STATE_HAS_DATA;
+      buf[1] = m_data_out;
+      m_data_out_full = false;
+
+      if (m_ctrl.TXINTEN)
+      {
+        Log_WarningPrintf("Setting TX interrupt");
+        SetInterrupt();
+      }
+    }
+
+    Log_InfoPrintf("Out: %02X %02X", buf[0], buf[1]);
+    if (m_connection->Write(buf, sizeof(buf)) != sizeof(buf))
+      Log_WarningPrintf("Write failed");
+  }
+
+  UpdateTXRX();
+}

src/core/sio.h

@@ -3,12 +3,14 @@
 #include "common/fifo_queue.h"
 #include "types.h"
 #include <array>
+#include <atomic>
 #include <memory>
+#include <string>
 
 class StateWrapper;
+class TimingEvent;
 
-class Controller;
-class MemoryCard;
+class SIOConnection;
 
 class SIO
 {
@@ -24,7 +26,14 @@ public:
   u32 ReadRegister(u32 offset);
   void WriteRegister(u32 offset, u32 value);
 
+  void DrawDebugStateWindow();
+
 private:
+  enum : u32
+  {
+    RX_FIFO_SIZE = 8
+  };
+
   union SIO_CTRL
   {
     u16 bits;
@@ -39,7 +48,7 @@ private:
     BitField<u16, u8, 8, 2> RXIMODE;
     BitField<u16, bool, 10, 1> TXINTEN;
     BitField<u16, bool, 11, 1> RXINTEN;
-    BitField<u16, bool, 12, 1> ACKINTEN;
+    BitField<u16, bool, 12, 1> DTRINTEN;
   };
 
   union SIO_STAT
@@ -53,7 +62,7 @@ private:
     BitField<u32, bool, 4, 1> RXFIFOOVERRUN;
     BitField<u32, bool, 5, 1> RXBADSTOPBIT;
     BitField<u32, bool, 6, 1> RXINPUTLEVEL;
-    BitField<u32, bool, 7, 1> DSRINPUTLEVEL;
+    BitField<u32, bool, 7, 1> DTRINPUTLEVEL;
     BitField<u32, bool, 8, 1> CTSINPUTLEVEL;
     BitField<u32, bool, 9, 1> INTR;
     BitField<u32, u32, 11, 15> TMR;
@@ -70,12 +79,56 @@ private:
     BitField<u16, u8, 6, 2> stop_bit_length;
   };
 
+  TickCount GetTicksBetweenTransfers() const;
+
   void SoftReset();
 
-  SIO_CTRL m_SIO_CTRL = {};
-  SIO_STAT m_SIO_STAT = {};
-  SIO_MODE m_SIO_MODE = {};
-  u16 m_SIO_BAUD = 0;
+  void UpdateTXRX();
+  void SetInterrupt();
+
+  void UpdateEvent();
+  void TransferEvent();
+  void TransferWithoutSync();
+  void TransferWithSync();
+
+  std::unique_ptr<SIOConnection> m_connection;
+  std::unique_ptr<TimingEvent> m_transfer_event;
+
+  SIO_CTRL m_ctrl = {};
+  SIO_STAT m_stat = {};
+  SIO_MODE m_mode = {};
+  u16 m_baud_rate = 0;
+
+  InlineFIFOQueue<u8, RX_FIFO_SIZE> m_data_in;
+
+  u8 m_data_out = 0;
+  bool m_data_out_full = false;
+  bool m_latched_txen = false;
+
+  bool m_sync_mode = true;
+  bool m_sync_last_cts = false;
+  bool m_sync_last_dtr = false;
+  bool m_sync_last_rts = false;
+  bool m_sync_remote_rts = false;
+};
+
+class SIOConnection
+{
+public:
+  virtual ~SIOConnection() = default;
+
+  static std::unique_ptr<SIOConnection> CreateSocketServer(std::string hostname, u32 port);
+  static std::unique_ptr<SIOConnection> CreateSocketClient(std::string hostname, u32 port);
+
+  ALWAYS_INLINE bool HasData() const { return m_data_ready.load(); }
+  ALWAYS_INLINE bool IsConnected() const { return m_connected.load(); }
+
+  virtual u32 Read(void* buffer, u32 buffer_size, u32 min_size) = 0;
+  virtual u32 Write(const void* buffer, u32 buffer_size) = 0;
+
+protected:
+  std::atomic_bool m_connected{false};
+  std::atomic_bool m_data_ready{false};
 };
 
 extern SIO g_sio;

src/core/sio_connection.cpp

@@ -0,0 +1,499 @@
+#include "sio_connection.h"
+#include "common/log.h"
+#include "common/string.h"
+#include <cstdarg>
+Log_SetChannel(SIOConnection);
+
+#ifdef _WIN32
+#include <WS2tcpip.h>
+#pragma comment(lib, "ws2_32.lib")
+#define SOCKET_ERROR_WOULD_BLOCK WSAEWOULDBLOCK
+#else
+#define SOCKET_ERROR_WOULD_BLOCK EWOULDBLOCK
+#define INVALID_SOCKET -1
+#endif
+
+static void CloseSocket(SocketType fd)
+{
+#ifdef _WIN32
+  closesocket(fd);
+#else
+  close(fd);
+#endif
+}
+
+static int GetSocketError()
+{
+#ifdef _WIN32
+  return WSAGetLastError();
+#else
+  return errno;
+#endif
+}
+
+static void PrintSocketError(const char* format, ...)
+{
+  std::va_list ap;
+  va_start(ap, format);
+
+  SmallString str;
+  str.FormatVA(format, ap);
+  va_end(ap);
+
+  Log_ErrorPrintf("%s: %d", str.GetCharArray(), GetSocketError());
+}
+
+static bool SetSocketNonblocking(SocketType socket, bool nonblocking)
+{
+#ifdef WIN32
+  u_long value = nonblocking ? 1 : 0;
+  if (ioctlsocket(socket, FIONBIO, &value) != 0)
+  {
+    PrintSocketError("ioctlsocket(%s)", nonblocking ? "nonblocking" : "blocking");
+    return false;
+  }
+
+  return true;
+#else
+  return false;
+#endif
+}
+
+SIOSocketConnection::SIOSocketConnection(std::string hostname, u32 port)
+  : m_hostname(std::move(hostname)), m_port(port), m_client_fd(INVALID_SOCKET)
+{
+}
+
+SIOSocketConnection::~SIOSocketConnection()
+{
+  if (m_client_fd != INVALID_SOCKET)
+    CloseSocket(m_client_fd);
+
+#ifdef WIN32
+  if (m_client_event != NULL)
+    WSACloseEvent(m_client_event);
+
+  if (m_want_write_event != NULL)
+    CloseHandle(m_want_write_event);
+
+  if (m_sockets_initialized)
+    WSACleanup();
+#endif
+}
+
+bool SIOSocketConnection::Initialize()
+{
+#ifdef _WIN32
+  WSADATA wd = {};
+  if (WSAStartup(MAKEWORD(2, 0), &wd) != 0)
+  {
+    PrintSocketError("WSAStartup() failed");
+    return false;
+  }
+
+  m_sockets_initialized = true;
+#endif
+
+#ifdef _WIN32
+  m_client_event = WSACreateEvent();
+  m_want_write_event = CreateEvent(nullptr, FALSE, FALSE, nullptr);
+  if (m_client_event == NULL || m_want_write_event == NULL)
+    return false;
+#endif
+
+  return true;
+}
+
+u32 SIOSocketConnection::Read(void* buffer, u32 buffer_size, u32 min_size)
+{
+  std::unique_lock lock(m_buffer_mutex);
+  if (m_read_buffer.empty() || m_client_fd < 0)
+  {
+    m_data_ready.store(false);
+    return 0;
+  }
+
+  if (m_read_buffer.size() < min_size)
+    return 0;
+
+  const u32 to_read = std::min<u32>(static_cast<u32>(m_read_buffer.size()), buffer_size);
+  if (to_read > 0)
+  {
+    std::memcpy(buffer, m_read_buffer.data(), to_read);
+    if (to_read == m_read_buffer.size())
+    {
+      m_read_buffer.clear();
+    }
+    else
+    {
+      const size_t new_size = m_read_buffer.size() - to_read;
+      std::memmove(&m_read_buffer[0], &m_read_buffer[to_read], new_size);
+      m_read_buffer.resize(new_size);
+    }
+  }
+
+  m_data_ready.store(!m_read_buffer.empty());
+  return to_read;
+}
+
+u32 SIOSocketConnection::Write(const void* buffer, u32 buffer_size)
+{
+  std::unique_lock lock(m_buffer_mutex);
+  if (m_client_fd < 0)
+    return 0;
+
+  // TODO: Max buffer size
+  const u32 to_write = buffer_size;
+  const size_t current_size = m_write_buffer.size();
+  m_write_buffer.resize(m_write_buffer.size() + buffer_size);
+  std::memcpy(&m_write_buffer[current_size], buffer, buffer_size);
+
+#ifdef _WIN32
+  SetEvent(m_want_write_event);
+#else
+#endif
+
+  return to_write;
+}
+
+void SIOSocketConnection::StartThread()
+{
+  m_thread = std::thread([this]() { SocketThread(); });
+}
+
+void SIOSocketConnection::ShutdownThread()
+{
+  if (!m_thread.joinable())
+    return;
+
+  m_thread_shutdown.store(true);
+
+#ifdef _WIN32
+  SetEvent(m_want_write_event);
+#endif
+
+  m_thread.join();
+}
+
+void SIOSocketConnection::HandleRead()
+{
+  std::unique_lock lock(m_buffer_mutex);
+
+  size_t current_size = m_read_buffer.size();
+  size_t buffer_size = std::max<size_t>(m_read_buffer.size() * 2, 128);
+  m_read_buffer.resize(buffer_size);
+
+  int nbytes = recv(m_client_fd, reinterpret_cast<char*>(&m_read_buffer[current_size]),
+                    static_cast<int>(buffer_size - current_size), 0);
+  if (nbytes <= 0)
+  {
+    m_read_buffer.resize(current_size);
+    if (GetSocketError() == SOCKET_ERROR_WOULD_BLOCK)
+      return;
+
+    PrintSocketError("recv() failed");
+    Disconnect();
+    return;
+  }
+  else if (nbytes == 0)
+  {
+    Log_InfoPrint("Client disconnected.");
+    Disconnect();
+    return;
+  }
+
+  m_read_buffer.resize(current_size + static_cast<size_t>(nbytes));
+  m_data_ready.store(true);
+}
+
+void SIOSocketConnection::HandleWrite()
+{
+  std::unique_lock lock(m_buffer_mutex);
+  if (m_write_buffer.empty())
+    return;
+
+  int nbytes =
+    send(m_client_fd, reinterpret_cast<const char*>(m_write_buffer.data()), static_cast<int>(m_write_buffer.size()), 0);
+  if (nbytes < 0)
+  {
+    if (GetSocketError() == SOCKET_ERROR_WOULD_BLOCK)
+      return;
+
+    PrintSocketError("send() failed");
+    Disconnect();
+    return;
+  }
+
+  if (nbytes == static_cast<int>(m_write_buffer.size()))
+  {
+    m_write_buffer.clear();
+    return;
+  }
+
+  const size_t new_size = m_write_buffer.size() - static_cast<size_t>(nbytes);
+  std::memmove(&m_write_buffer[0], &m_write_buffer[static_cast<size_t>(nbytes)], new_size);
+  m_write_buffer.resize(new_size);
+}
+
+void SIOSocketConnection::HandleClose()
+{
+  Log_InfoPrint("Client disconnected.");
+  Disconnect();
+}
+
+void SIOSocketConnection::Disconnect()
+{
+  CloseSocket(m_client_fd);
+  m_client_fd = INVALID_SOCKET;
+  m_read_buffer.clear();
+  m_write_buffer.clear();
+  m_connected.store(false);
+  m_data_ready.store(false);
+}
+
+std::unique_ptr<SIOConnection> SIOConnection::CreateSocketServer(std::string hostname, u32 port)
+{
+  std::unique_ptr<SIOSocketServerConnection> server(new SIOSocketServerConnection(std::move(hostname), port));
+  if (!server->Initialize())
+    return {};
+
+  return server;
+}
+
+SIOSocketServerConnection::SIOSocketServerConnection(std::string hostname, u32 port)
+  : SIOSocketConnection(std::move(hostname), port), m_accept_fd(INVALID_SOCKET)
+{
+}
+
+SIOSocketServerConnection::~SIOSocketServerConnection()
+{
+  ShutdownThread();
+
+  if (m_accept_fd != INVALID_SOCKET)
+    CloseSocket(m_accept_fd);
+
+  if (m_accept_event != NULL)
+    WSACloseEvent(m_accept_event);
+}
+
+bool SIOSocketServerConnection::Initialize()
+{
+  if (!SIOSocketConnection::Initialize())
+    return false;
+
+  sockaddr_in addr = {};
+  addr.sin_family = AF_INET;
+  addr.sin_port = htons(static_cast<u16>(m_port));
+
+  m_accept_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+  if (m_accept_fd == INVALID_SOCKET)
+  {
+    PrintSocketError("socket() failed");
+    return false;
+  }
+
+  if (bind(m_accept_fd, reinterpret_cast<const sockaddr*>(&addr), sizeof(addr)) != 0)
+  {
+    PrintSocketError("bind() failed");
+    return false;
+  }
+
+  if (listen(m_accept_fd, 1) != 0)
+  {
+    PrintSocketError("listen() failed");
+    return false;
+  }
+
+#ifdef _WIN32
+  SetSocketNonblocking(m_accept_fd, true);
+
+  m_accept_event = WSACreateEvent();
+  if (m_accept_event == NULL)
+    return false;
+
+  if (WSAEventSelect(m_accept_fd, m_accept_event, FD_ACCEPT) != 0)
+  {
+    PrintSocketError("WSAEventSelect(FD_ACCEPT) failed");
+    return false;
+  }
+#endif
+
+  StartThread();
+  return true;
+}
+
+void SIOSocketServerConnection::SocketThread()
+{
+  while (!m_thread_shutdown.load())
+  {
+#ifdef _WIN32
+    const HANDLE event_handles[] = {m_want_write_event, m_accept_event, m_client_event};
+    const DWORD res = WSAWaitForMultipleEvents(countof(event_handles), event_handles, FALSE, 1000, FALSE);
+    if (res == WAIT_TIMEOUT)
+      continue;
+
+    WSANETWORKEVENTS ev;
+    if (WSAEnumNetworkEvents(m_accept_fd, m_accept_event, &ev) == 0)
+    {
+      if (ev.lNetworkEvents & FD_ACCEPT)
+        HandleAccept();
+    }
+
+    if (m_client_fd != INVALID_SOCKET)
+    {
+      if (WSAEnumNetworkEvents(m_client_fd, m_client_event, &ev) == 0)
+      {
+        if (ev.lNetworkEvents & FD_READ)
+          HandleRead();
+        if (ev.lNetworkEvents & FD_WRITE)
+          HandleWrite();
+        if (ev.lNetworkEvents & FD_CLOSE)
+          HandleClose();
+      }
+    }
+
+    if (m_client_fd != INVALID_SOCKET && res == WSA_WAIT_EVENT_0)
+      HandleWrite();
+#else
+#endif
+  }
+}
+
+void SIOSocketServerConnection::HandleAccept()
+{
+  sockaddr client_address = {};
+  int client_address_len = sizeof(client_address);
+  SocketType new_socket = accept(m_accept_fd, &client_address, &client_address_len);
+  if (new_socket == INVALID_SOCKET)
+  {
+    if (GetSocketError() != SOCKET_ERROR_WOULD_BLOCK)
+      PrintSocketError("accept() failed");
+
+    return;
+  }
+
+  if (m_client_fd != INVALID_SOCKET)
+  {
+    static const char error[] = "Client already connected.";
+    Log_WarningPrint("Dropping client connection because we're already connected");
+
+    // we already have a client
+    SetSocketNonblocking(new_socket, false);
+    send(new_socket, error, sizeof(error) - 1, 0);
+    CloseSocket(new_socket);
+    return;
+  }
+
+  SetSocketNonblocking(new_socket, true);
+
+#ifdef _WIN32
+  if (WSAEventSelect(new_socket, m_client_event, FD_READ | FD_WRITE | FD_CLOSE) != 0)
+  {
+    PrintSocketError("WSAEventSelect(FD_READ | FD_WRITE | FD_CLOSE) failed");
+    CloseSocket(new_socket);
+  }
+#endif
+
+  std::unique_lock lock(m_buffer_mutex);
+  Log_InfoPrintf("Client connection accepted: %d", new_socket);
+  m_client_fd = new_socket;
+  m_connected.store(true);
+}
+
+SIOSocketClientConnection::SIOSocketClientConnection(std::string hostname, u32 port)
+  : SIOSocketConnection(std::move(hostname), port)
+{
+}
+
+SIOSocketClientConnection::~SIOSocketClientConnection()
+{
+  ShutdownThread();
+}
+
+bool SIOSocketClientConnection::Initialize()
+{
+  if (!SIOSocketConnection::Initialize())
+    return false;
+
+  struct addrinfo hints = {};
+  hints.ai_family = AF_UNSPEC;
+  hints.ai_socktype = SOCK_STREAM;
+
+  struct addrinfo* ai;
+  int err = getaddrinfo(m_hostname.c_str(), TinyString::FromFormat("%u", m_port), &hints, &ai);
+  if (err != 0)
+  {
+    Log_ErrorPrintf("getaddrinfo(%s:%u) failed: %d", m_hostname.c_str(), m_port, err);
+    return false;
+  }
+
+  m_client_fd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
+  if (m_client_fd == INVALID_SOCKET)
+  {
+    PrintSocketError("socket() failed");
+    freeaddrinfo(ai);
+    return false;
+  }
+
+  err = connect(m_client_fd, ai->ai_addr, static_cast<int>(ai->ai_addrlen));
+  freeaddrinfo(ai);
+  if (err != 0)
+  {
+    PrintSocketError("connect() failed");
+    return false;
+  }
+
+  SetSocketNonblocking(m_client_fd, true);
+
+#ifdef _WIN32
+  if (WSAEventSelect(m_client_fd, m_client_event, FD_READ | FD_WRITE | FD_CLOSE) != 0)
+  {
+    PrintSocketError("WSAEventSelect(FD_READ | FD_WRITE | FD_CLOSE) failed");
+    CloseSocket(m_client_fd);
+  }
+#endif
+
+  m_connected.store(true);
+  StartThread();
+  return true;
+}
+
+void SIOSocketClientConnection::SocketThread()
+{
+  while (!m_thread_shutdown.load())
+  {
+#ifdef _WIN32
+    HANDLE event_handles[] = {m_want_write_event, m_client_event};
+    DWORD res = WSAWaitForMultipleEvents(countof(event_handles), event_handles, FALSE, 1000, FALSE);
+    if (res == WAIT_TIMEOUT)
+      continue;
+
+    WSANETWORKEVENTS ev;
+    if (m_client_fd != INVALID_SOCKET)
+    {
+      if (WSAEnumNetworkEvents(m_client_fd, m_client_event, &ev) == 0)
+      {
+        if (ev.lNetworkEvents & FD_READ)
+          HandleRead();
+        if (ev.lNetworkEvents & FD_WRITE)
+          HandleWrite();
+        if (ev.lNetworkEvents & FD_CLOSE)
+          HandleClose();
+      }
+    }
+
+    if (m_client_fd != INVALID_SOCKET && res == WSA_WAIT_EVENT_0)
+      HandleWrite();
+#else
+#endif
+  }
+}
+
+std::unique_ptr<SIOConnection> SIOConnection::CreateSocketClient(std::string hostname, u32 port)
+{
+  std::unique_ptr<SIOSocketClientConnection> server(new SIOSocketClientConnection(std::move(hostname), port));
+  if (!server->Initialize())
+    return {};
+
+  return server;
+}

src/core/sio_connection.h

@@ -0,0 +1,90 @@
+#pragma once
+#include "sio.h"
+#include "types.h"
+#include <atomic>
+#include <memory>
+#include <mutex>
+#include <thread>
+#include <vector>
+
+#ifdef _WIN32
+#include "common/windows_headers.h"
+#include <WinSock2.h>
+#endif
+
+#ifdef _WIN32
+using SocketType = SOCKET;
+#else
+using SocketType = int;
+#endif
+
+class SIOSocketConnection : public SIOConnection
+{
+public:
+  SIOSocketConnection(std::string hostname, u32 port);
+  ~SIOSocketConnection() override;
+
+  virtual bool Initialize();
+
+  u32 Read(void* buffer, u32 buffer_size, u32 min_size) override;
+  u32 Write(const void* buffer, u32 buffer_size) override;
+
+protected:
+  virtual void SocketThread() = 0;
+
+  void StartThread();
+  void ShutdownThread();
+
+  void HandleRead();
+  void HandleWrite();
+  void HandleClose();
+  void Disconnect();
+
+  std::string m_hostname;
+  std::thread m_thread;
+  std::atomic_bool m_thread_shutdown{false};
+  u32 m_port = 0;
+  SocketType m_client_fd;
+
+  std::mutex m_buffer_mutex;
+  std::vector<u8> m_read_buffer;
+  std::vector<u8> m_write_buffer;
+
+#ifdef _WIN32
+  HANDLE m_client_event = NULL;
+  HANDLE m_want_write_event = NULL;
+  bool m_sockets_initialized = false;
+#endif
+};
+
+class SIOSocketServerConnection : public SIOSocketConnection
+{
+public:
+  SIOSocketServerConnection(std::string hostname, u32 port);
+  ~SIOSocketServerConnection() override;
+
+  bool Initialize() override;
+
+protected:
+  void SocketThread() override;
+
+  void HandleAccept();
+  
+  SocketType m_accept_fd;
+
+#ifdef _WIN32
+  HANDLE m_accept_event = NULL;
+#endif
+};
+
+class SIOSocketClientConnection : public SIOSocketConnection
+{
+public:
+  SIOSocketClientConnection(std::string hostname, u32 port);
+  ~SIOSocketClientConnection() override;
+
+  bool Initialize() override;
+
+protected:
+  void SocketThread() override;
+};

src/duckstation-qt/mainwindow.cpp

@@ -1133,6 +1133,7 @@ void MainWindow::connectSignals()
   SettingWidgetBinder::BindWidgetToBoolSetting(m_host_interface, m_ui.actionDebugShowMDECState, "Debug",
                                                "ShowMDECState");
   SettingWidgetBinder::BindWidgetToBoolSetting(m_host_interface, m_ui.actionDebugShowDMAState, "Debug", "ShowDMAState");
+  SettingWidgetBinder::BindWidgetToBoolSetting(m_host_interface, m_ui.actionDebugShowSIOState, "Debug", "ShowSIOState");
 
   addThemeToMenu(tr("Default"), QStringLiteral("default"));
   addThemeToMenu(tr("Fusion"), QStringLiteral("fusion"));

src/duckstation-qt/mainwindow.ui

@@ -193,6 +193,7 @@
     <addaction name="actionDebugShowTimersState"/>
     <addaction name="actionDebugShowMDECState"/>
     <addaction name="actionDebugShowDMAState"/>
+    <addaction name="actionDebugShowSIOState"/>
    </widget>
    <widget class="QMenu" name="menu_View">
     <property name="title">
@@ -701,6 +702,14 @@
     <string>Show DMA State</string>
    </property>
   </action>
+  <action name="actionDebugShowSIOState">
+   <property name="checkable">
+    <bool>true</bool>
+   </property>
+   <property name="text">
+    <string>Show SIO State</string>
+   </property>
+  </action>
   <action name="actionScreenshot">
    <property name="icon">
     <iconset resource="resources/resources.qrc">

src/frontend-common/common_host_interface.cpp

@@ -16,6 +16,7 @@
 #include "core/mdec.h"
 #include "core/pgxp.h"
 #include "core/save_state_version.h"
+#include "core/sio.h"
 #include "core/spu.h"
 #include "core/system.h"
 #include "core/texture_replacements.h"
@@ -1254,6 +1255,8 @@ void CommonHostInterface::DrawDebugWindows()
     g_mdec.DrawDebugStateWindow();
   if (g_settings.debugging.show_dma_state)
     g_dma.DrawDebugStateWindow();
+  if (g_settings.debugging.show_sio_state)
+    g_sio.DrawDebugStateWindow();
 }
 
 bool CommonHostInterface::IsCheevosChallengeModeActive() const
@@ -2655,6 +2658,7 @@ void CommonHostInterface::FixIncompatibleSettings(bool display_osd_messages)
     g_settings.debugging.show_timers_state = false;
     g_settings.debugging.show_mdec_state = false;
     g_settings.debugging.show_dma_state = false;
+    g_settings.debugging.show_sio_state = false;
     g_settings.debugging.dump_cpu_to_vram_copies = false;
     g_settings.debugging.dump_vram_to_cpu_copies = false;
   }