diff --git a/control_seekat_demo.py b/control_seekat_demo.py
index 66ff9c4..5bf5925 100644
--- a/control_seekat_demo.py
+++ b/control_seekat_demo.py
@@ -1,10 +1,42 @@
 import gi
 gi.require_version("Gtk", "3.0")
 from gi.repository import Gtk
+import serial
+import serial.tools.list_ports
+
+class SerComm:
+	def refresh(self, _):
+# Does this cause a memory error? This is a GTK interned string
+		curid = self.sel_box.get_active_id()
+
+		self.sel_box.remove_all()
+		self.sel_box.append(None, "(select device)")
+		self.sel_box.set_active(0)
+		for (nm, desc, id) in serial.tools.list_ports.comports():
+			s = nm
+			if desc != "n/a":
+				s = s + f" - {desc}"
+			if id != "n/a":
+				s = s + f" - {id}"
+			self.sel_box.append(nm, s)
+			if curid == nm:
+				self.sel_box.set_active_id(nm)
+
+	def __init__(self, getobj):
+		self.getobj = getobj
+		self.ser = serial.Serial()
+		self.ser.baudrate = 115200
+
+		self.sel_box = getobj("sel_box")
 
 if __name__ == "__main__":
 	builder = Gtk.Builder()
 	builder.add_from_file("gui.glade")
 	builder.get_object("win").connect("destroy", Gtk.main_quit)
 	builder.get_object("win").show_all()
+
+	sc = SerComm(builder.get_object)
+	builder.get_object("sel_ref").connect("clicked", sc.refresh)
+	sc.refresh(None)
+
 	Gtk.main()