initial pass at having a ui update at regular intervales

main.kv

@@ -0,0 +1,21 @@
+<MyLabel@Label>:
+    text: 'Current Temperature: n/a'
+#    on_lastTemperature: self.update_current_temperature_label()
+
+<MainWindow>:
+    label_wid: "Temperature Monitor"
+    BoxLayout:
+        orientation: 'vertical'
+        BoxLayout:
+            size_hint_y: 0.1
+            orientation: 'horizontal'
+            MyLabel:
+                id: 'current_temperature'
+            Button:
+                text: 'Start/Stop'
+            Label:
+                text: 'No File Chosen'
+            Label:
+                text: 'Data Source'
+        Label:
+            text: 'Graph placeholder'

main.py

@@ -1,21 +1,71 @@
 import kivy
 from kivy.app import App
-from kivy.uix.label import Label
+from kivy.clock import Clock
+from kivy.logger import Logger
+from kivy.properties import ObjectProperty, StringProperty
 from kivy.uix.boxlayout import BoxLayout
+from kivy.uix.floatlayout import FloatLayout
+from kivy.uix.label import Label
+import kivy.lang
+import Queue
+import temp_log
+import threading
 
-class MyApp(App):
+dataThread = None
+dataThreadDataQueue = Queue.Queue()
+dataThreadCommandQueue = Queue.Queue()
+
+class MainApp(App):
 
     def build(self):
-        return Label(text=unicode('Temperature Logger'))
+        mainWindow = MainWindow()
+        Clock.schedule_interval(mainWindow.update_last_temperature, 0.25)
+        return mainWindow
 
-class MainScreen(BoxLayout):
 
-    def __init__(self, **kwargs):
-        super(MainScreen, self).__init__(**kwargs)
-        self.orientation = 'vertical'
-        top = new BoxLayout(orientation = 'horizontal')
-        self.add_widget(top)
+    def on_stop(self):
+        global dataThreadCommandQueue
+        dataThreadCommandQueue.put_nowait('stop')
+
+
+    def on_start(self):
+        global dataThread
+        dataThread.start()
+
+
+class MainWindow(FloatLayout):
+    """Main Window class"""
+    dataSource = StringProperty('/dev/ttyACM0')
+    lastTemperature = StringProperty('n/a')
+
+    def update_last_temperature(self, dt):
+        global dataThreadDataQueue
+        # This breaks if there are more updates in the queue than the frequency of update_last_temperature - it pulls old data out of the queue, and not the most recent.
+        try:
+            data = dataThreadDataQueue.get_nowait()
+            if data is not None:
+                self.lastTemperature = str(data['data']['temperature'])
+        except Queue.Empty:
             pass
 
+    def on_lastTemperature(self, instance, value):
+        Logger.debug('lastTemperature has changed to: ' + str(value))
+        children = self.children[:]
+        while children:
+            child = children.pop()
+            try:
+                child.on_lastTemperature(instance, value)
+            except Exception, e:
+                pass
+            children.extend(child.children)
+
+
+class MyLabel(Label):
+
+    def on_lastTemperature(self, instance, value):
+        self.text = 'Current temperature: ' + str(value)
+
+
 if __name__ == '__main__':
-    MyApp().run()
+    dataThread = threading.Thread(None, temp_log.threaded_reader, None, ['/dev/ttyACM0', dataThreadDataQueue, dataThreadCommandQueue])
+    MainApp().run()

temp_log.py

@@ -1,5 +1,10 @@
 #! /usr/bin/env python
-import serial, sys, time, io
+import io
+import Queue
+import serial
+import sys
+import threading
+import time
 defaultSerialPort = '/dev/ttyACM0'
 defaultVersion = 0
 
@@ -14,12 +19,42 @@ def parse_line(line, version = defaultVersion):
     data = {}
     if (version == 0):
         line = line.split(' ')
+        try:
             data['temperature'] = float(line[-2])
+        except Exception, e:
+            pass
     else:
         raise ParseException('Unimplemented line version', version)
     return data
 
 
+def threaded_reader(source, dataQueue, commandQueue):
+    import kivy.logger
+    ser = serial.Serial(source, baudrate=9600, parity=serial.PARITY_NONE, stopbits=serial.STOPBITS_ONE, bytesize=serial.EIGHTBITS)
+    sio = io.TextIOWrapper(io.BufferedRWPair(ser, ser))
+    ser.isOpen()
+    buffer = ''
+    runTime = ''
+    cmd = ''
+    while True:
+        try:
+            cmd = commandQueue.get_nowait()
+        except Queue.Empty:
+            pass
+        if cmd == 'stop':
+            break
+        try:
+            data = parse_line(ser.readline(), defaultVersion)
+            runTime = time.time()
+        except Exception, e:
+            kivy.logger.Logger.exception(e)
+            continue
+        if data and runTime:
+            item = {'time' : runTime, 'data' : data}
+            kivy.logger.Logger.debug(str(item))
+            dataQueue.put(item)
+
+
 def main(args = sys.argv):
     # @TODO switch to parse args or similar
     # @TODO parse of temperature logger line version
@@ -37,6 +72,7 @@ def main(args = sys.argv):
         try:
             buffer = ser.readline()
             data = parse_line(buffer, lineVersion)
+            if data:
                 print unicode(time.time()) + ',' + unicode(data['temperature'])
                 sys.stdout.flush()
         except Exception, e: