diff --git a/UI.py b/UI.py
new file mode 100644
index 00000000..cbe56bc6
--- /dev/null
+++ b/UI.py
@@ -0,0 +1,117 @@
+import tkinter as tk
+import tkinter.ttk as ttk
+from serial import Serial
+from serial.tools.list_ports import comports
+from tkinter.messagebox import showerror
+from threading import Thread, Lock, Event
+from serial import Serial, SerialException
+import sys
+
+S_OK: int = 0xaa
+S_ERR: int = 0xff
+
+class LockedSerial(Serial):
+    _lock: Lock = Lock()
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+    
+    def read(self, size=1) -> bytes:
+        with self._lock:
+            return super().read(size)
+
+    def write(self, b: bytes, /) -> int | None:
+        with self._lock:
+            super().write(b)
+
+    def close(self):
+        with self._lock:
+            super().close()
+
+
+class App(tk.Tk):
+    ser: LockedSerial
+    def __init__(self):
+        super().__init__()
+
+        self.title("LED Blinker")  
+        self.protocol("WM_DELETE_WINDOW", self.on_close)  # Bind close button to on_close
+        self.stop_event = Event()
+        self.port = tk.StringVar()
+        self.led = tk.BooleanVar()
+
+        ttk.Checkbutton(self, text='Toggle LED', variable=self.led, command=self.update_led).pack()
+        ttk.Button(self, text='Send Invalid', command=self.send_invalid).pack()
+        ttk.Button(self, text='Disconnect', command=self.disconnect,default='active').pack()
+
+        SerialPortal(self)
+
+    def detached_callback(f):
+        return lambda *args, **kwargs: Thread(target=f, args=args, kwargs=kwargs).start()
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, *_):
+        self.disconnect()
+        
+    def disconnect(self):
+        self.ser.close()
+
+        SerialPortal(self)
+
+    def send_invalid(self):
+        self.write(bytes([0x10]))
+
+    def connect(self):
+        self.ser = LockedSerial(self.port.get())
+
+    @detached_callback     
+    def update_led(self):
+        #value = self.led.get()
+        self.write(bytes([self.led.get()]))
+
+    def send_invalid(self):
+        self.write(bytes([0x10]))
+        
+    def write(self, b: bytes):
+        try:
+            self.ser.write(b)
+            if int.from_bytes(self.ser.read(), 'big') == S_ERR:
+                showerror('Device Error', 'The device reported an invalid command.')
+        except SerialException:
+            showerror('Serial Error', 'Write failed.')
+    
+    def on_close(self):
+        self.stop_event.set() #signals threads to stop
+        self.disconnect()
+        self.destroy()
+        sys.exit()
+
+class SerialPortal(tk.Toplevel):
+    def __init__(self, parent: App):
+        super().__init__(parent)
+
+        self.parent = parent
+        self.protocol("WM_DELETE_WINDOW", self.on_close)  # Bind close button to on_close
+        self.parent.withdraw() # hide App until connected
+
+        ttk.OptionMenu(self, parent.port, '', *[d.device for d in comports()]).pack()
+        ttk.Button(self, text='Connect', command=self.connect, default='active').pack()
+
+    def connect(self):
+        self.parent.connect()
+        self.destroy()
+        self.parent.deiconify() # reveal App
+    # send `value` somehow??
+    
+    def on_close(self):
+        """Close the SerialPortal window and terminate the application."""
+        self.parent.on_close()  # Call the main app's on_close method to ensure cleanup
+        self.destroy()  # Ensure the SerialPortal window is closed
+
+
+if __name__ == '__main__':
+    with App() as app:
+        app.mainloop()
+