diff --git a/KeyBorad/KeyBorad/LOGIC/Lgc_Core.cpp b/KeyBorad/KeyBorad/LOGIC/Lgc_Core.cpp
index caadf38..72e4039 100644
--- a/KeyBorad/KeyBorad/LOGIC/Lgc_Core.cpp
+++ b/KeyBorad/KeyBorad/LOGIC/Lgc_Core.cpp
@@ -1,5 +1,67 @@
 #include "LOGIC/Lgc_Core.h"
 
+#include "COM/Com_ProtoCodec.h"
+
+namespace
+{
+
+void Lgc_Func_ApplyHelloRsp(
+    Lgc_Core* p_Core,
+    const Packet_HelloRsp& HelloRsp)
+{
+    p_Core->State.IsConnected = true;
+    p_Core->State.IsHandshakeDone = true;
+    p_Core->State.ProtocolVersion = HelloRsp.ProtocolVersion;
+    p_Core->State.VendorId = HelloRsp.VendorId;
+    p_Core->State.ProductId = HelloRsp.ProductId;
+    p_Core->State.FirmwareMajor = HelloRsp.FirmwareMajor;
+    p_Core->State.FirmwareMinor = HelloRsp.FirmwareMinor;
+    p_Core->State.CapabilityFlags = HelloRsp.CapabilityFlags;
+    p_Core->State.ActiveTransport = Lgc_TransportType::Cdc;
+    p_Core->State.ActiveEndpointName = p_Core->Session.CdcPort.PortName;
+    p_Core->State.ConnectionText = QStringLiteral("CDC connected: %1")
+        .arg(p_Core->Session.CdcPort.PortName);
+    p_Core->State.LastActionText = QStringLiteral("Handshake completed.");
+}
+
+void Lgc_Func_UpdateActionText(Lgc_Core* p_Core, const Packet& PacketData)
+{
+    switch (PacketData.type)
+    {
+    case Com_Type_HelloRsp:
+        p_Core->State.LastActionText = QStringLiteral("Received HelloRsp.");
+        break;
+    case Com_Type_Bitmap:
+        p_Core->State.LastActionText = QStringLiteral("Received Bitmap.");
+        break;
+    case Com_Type_FunctionKeyEvent:
+        p_Core->State.LastActionText = QStringLiteral("Received FunctionKeyEvent.");
+        break;
+    case Com_Type_LedState:
+        p_Core->State.LastActionText = QStringLiteral("Received LedState.");
+        break;
+    case Com_Type_TimeSync:
+        p_Core->State.LastActionText = QStringLiteral("Received TimeSync.");
+        break;
+    case Com_Type_ThemeRgb:
+        p_Core->State.LastActionText = QStringLiteral("Received ThemeRgb.");
+        break;
+    case Com_Type_Ack:
+        p_Core->State.LastActionText = QStringLiteral("Received Ack.");
+        break;
+    case Com_Type_Error:
+        p_Core->State.LastActionText = QStringLiteral("Received Error.");
+        break;
+    default:
+        p_Core->State.LastActionText = QStringLiteral("Received packet type 0x%1.")
+            .arg(static_cast<quint8>(PacketData.type), 2, 16, QLatin1Char('0'))
+            .toUpper();
+        break;
+    }
+}
+
+} // namespace
+
 void Lgc_Core_Init(Lgc_Core* p_Core)
 {
     if (p_Core == nullptr)
@@ -11,6 +73,45 @@ void Lgc_Core_Init(Lgc_Core* p_Core)
     Lgc_Session_Init(&p_Core->Session);
 }
 
+bool Lgc_Core_Start(Lgc_Core* p_Core)
+{
+    if (p_Core == nullptr)
+    {
+        return false;
+    }
+
+    Dri_Cdc_Struct_OpenConfig Config;
+    Packet_HelloRsp HelloRsp;
+    if (Lgc_Session_TryStartCdc(&p_Core->Session, Config, &HelloRsp))
+    {
+        Lgc_Func_ApplyHelloRsp(p_Core, HelloRsp);
+        return true;
+    }
+
+    p_Core->State.IsConnected = false;
+    p_Core->State.IsHandshakeDone = false;
+    p_Core->State.ConnectionText = QStringLiteral("No device found.");
+    p_Core->State.LastActionText = QStringLiteral("Handshake failed.");
+    return false;
+}
+
+bool Lgc_Core_Poll(Lgc_Core* p_Core)
+{
+    if (p_Core == nullptr)
+    {
+        return false;
+    }
+
+    Packet PacketData;
+    if (!Lgc_Session_ReadNextPacket(&p_Core->Session, &PacketData))
+    {
+        return false;
+    }
+
+    Lgc_Func_UpdateActionText(p_Core, PacketData);
+    return true;
+}
+
 void Lgc_Core_Close(Lgc_Core* p_Core)
 {
     if (p_Core == nullptr)
@@ -21,3 +122,8 @@ void Lgc_Core_Close(Lgc_Core* p_Core)
     Lgc_Session_Close(&p_Core->Session);
     p_Core->State = Lgc_State();
 }
+
+const Lgc_State& Lgc_Core_GetState(const Lgc_Core* p_Core)
+{
+    return p_Core->State;
+}
diff --git a/KeyBorad/KeyBorad/LOGIC/Lgc_Core.h b/KeyBorad/KeyBorad/LOGIC/Lgc_Core.h
index 19aace6..126be6a 100644
--- a/KeyBorad/KeyBorad/LOGIC/Lgc_Core.h
+++ b/KeyBorad/KeyBorad/LOGIC/Lgc_Core.h
@@ -10,4 +10,7 @@ struct Lgc_Core
 };
 
 void Lgc_Core_Init(Lgc_Core* p_Core);
+bool Lgc_Core_Start(Lgc_Core* p_Core);
+bool Lgc_Core_Poll(Lgc_Core* p_Core);
 void Lgc_Core_Close(Lgc_Core* p_Core);
+const Lgc_State& Lgc_Core_GetState(const Lgc_Core* p_Core);
diff --git a/docs/host_logic_rebuild.md b/docs/host_logic_rebuild.md
index 50bd357..c0b9bd7 100644
--- a/docs/host_logic_rebuild.md
+++ b/docs/host_logic_rebuild.md
@@ -63,13 +63,15 @@ Implemented behavior:
 
 ### Node 4: core facade
 
-Files planned after session:
+Files completed in this step:
 
 - `KeyBorad/KeyBorad/LOGIC/Lgc_Core.h`
 - `KeyBorad/KeyBorad/LOGIC/Lgc_Core.cpp`
 
-Target behavior:
+Implemented behavior:
 
 - give APP one small entry point
-- forward start/poll/close to session
-- refresh state from handshake results
+- start CDC handshake through session
+- expose `Start / Poll / Close / GetState`
+- refresh state from `HelloRsp`
+- update a simple action text when packets arrive