Implement DFU mode

pytec/pytec/aioclient.py

@@ -240,3 +240,16 @@ class Client:
             await self._writer.drain()
 
         await self.disconnect()
+
+    async def dfu(self):
+        """Put the Thermostat in DFU update mode
+        
+        The client is disconnected as the Thermostat stops responding to
+        TCP commands in DFU update mode. The only way to exit it is by
+        power-cycling.
+        """
+        async with self._command_lock:
+            self._writer.write("dfu\n".encode('utf-8'))
+            await self._writer.drain()
+
+        await self.disconnect()

pytec/tec_qt.py

@@ -320,7 +320,16 @@ class MainWindow(QtWidgets.QMainWindow, Ui_MainWindow):
         self.actionReset.triggered.connect(reset_thermostat)
         self.thermostat_menu.addAction(self.actionReset)
 
+        @asyncSlot(bool)
+        async def dfu_mode(_):
+            await self._on_connection_changed(False)
+            await self.client.dfu()
+
+            # TODO: add a firmware flashing GUI?
+
+        self.actionEnter_DFU_Mode.triggered.connect(dfu_mode)
         self.thermostat_menu.addAction(self.actionEnter_DFU_Mode)
+
         self.thermostat_menu.addAction(self.actionNetwork_Settings)
         self.thermostat_menu.addAction(self.actionLoad_all_configs)
         self.thermostat_menu.addAction(self.actionSave_all_configs)