diff --git a/control_seekat_demo.py b/control_seekat_demo.py
index 5bf5925..ec3db20 100644
--- a/control_seekat_demo.py
+++ b/control_seekat_demo.py
@@ -3,8 +3,61 @@ gi.require_version("Gtk", "3.0")
 from gi.repository import Gtk
 import serial
 import serial.tools.list_ports
+import re
+
+def error_popup(parent, msg):
+	box = Gtk.MessageDialog(
+		parent=parent,
+		modal=True,
+		destroy_with_parent=True,
+		message_type=Gtk.MessageType.ERROR,
+		buttons=Gtk.ButtonsType.CLOSE,
+		text = msg
+	)
+	box.connect("response", lambda _0, _1: box.close())
+	box.show_all()
 
 class SerComm:
+	def error_popup(self, x):
+		error_popup(self.getobj("win"), x)
+
+	def get_or_to(self):
+		s = self.ser.read_until().decode()
+		if not s:
+			raise Exception(f"DAC timeout: '{s}'")
+		return s.rstrip("\r\n")
+
+	def connect(self):
+		s = self.sel_box.get_active_id()
+		if self.ser.is_open:
+			self.ser.close()
+
+		if s == None:
+			self.getobj("dac_idn").set_label("(disconnected)")
+			return None
+
+		self.ser.port = s
+		self.ser.open()
+
+		while True:
+			s = self.get_or_to()
+			if s == "INITIALIZATION COMPLETE":
+				break
+
+			loc = re.search(r'[0-9]', s)
+			if loc is None:
+				raise Exception(f"Unknown message from DAC: '{s}'")
+			self.getobj(f"Ch{int(loc.group(0)) + 1}").set_label('<span color="red">ERR</span>')
+
+		self.ser.write(b"*IDN?\r\n")
+		self.getobj("dac_idn").set_label(self.get_or_to())
+
+	def on_connect(self, _):
+		try:
+			self.connect()
+		except Exception as e:
+			self.error_popup(str(e))			
+
 	def refresh(self, _):
 # Does this cause a memory error? This is a GTK interned string
 		curid = self.sel_box.get_active_id()
@@ -12,6 +65,7 @@ class SerComm:
 		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":
@@ -24,11 +78,15 @@ class SerComm:
 
 	def __init__(self, getobj):
 		self.getobj = getobj
-		self.ser = serial.Serial()
+		self.ser = serial.Serial(timeout=3)
 		self.ser.baudrate = 115200
 
 		self.sel_box = getobj("sel_box")
 
+		getobj("sel_ref").connect("clicked", self.refresh)
+		self.refresh(None)
+		getobj("sel_do").connect("clicked", self.on_connect)
+
 if __name__ == "__main__":
 	builder = Gtk.Builder()
 	builder.add_from_file("gui.glade")
@@ -36,7 +94,6 @@ if __name__ == "__main__":
 	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()