Add FM Demodulation

controller.py

@@ -25,12 +25,17 @@
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 from views import *
-
+import subprocess
 
 class FreqShowController(object):
 	"""Class which controls the views shown in the application and mediates
 	changing between views.
 	"""
+        rtl_fm_process = None
+        aplay_process = None
+        demodulating = False
+        prev_center_freq = 90.3
+
 	def __init__(self, model):
 		"""Initialize controller with specified FreqShow model."""
 		self.model = model
@@ -42,7 +47,32 @@ def __init__(self, model):
 		self._current_view = None
 		self.change_to_instant()
 
-	def change_view(self, view):
+        def demodulate(self, *args):
+            #kill the previous sub process
+            if self.rtl_fm_process is not None:
+                self.rtl_fm_process.terminate()
+
+            if self.aplay_process is not None:
+                self.aplay_process.terminate()
+
+            if not self.demodulating:
+                self.model.close_sdr()
+                self.prev_center_freq = self.model.get_center_freq()
+                freq = self.prev_center_freq * 1000000.0
+                self.rtl_fm_process = subprocess.Popen(["rtl_fm", "-M", "fm", "-s", "200000", "-r", "48000", "-f", str(freq) ], stdout=subprocess.PIPE)
+                self.aplay_process = subprocess.Popen(["aplay", "-r", "48000", "-f", "S16_LE"], stdin=self.rtl_fm_process.stdout)
+                self.demodulating = True
+            else:
+                #reopen sdr for system
+                self.model.open_sdr()
+                self.model.set_center_freq(self.prev_center_freq)
+                self.demodulating = False
+
+        def change_view(self, view):
+                #if currently demodulating stop
+                if self.demodulating:
+                    self.demodulate()
+
 		"""Change to specified view."""
 		self._prev_view = self._current_view
 		self._current_view = view

freqshow.py

@@ -101,4 +101,4 @@
 				fscontroller.current().click(pygame.mouse.get_pos())
 		# Update and render the current view.
 		fscontroller.current().render(screen)
-		pygame.display.update()
+		pygame.display.update()

model.py

@@ -26,7 +26,7 @@
 from rtlsdr import *
 
 import freqshow
-
+import time
 
 class FreqShowModel(object):
 	def __init__(self, width, height):
@@ -47,6 +47,14 @@ def __init__(self, width, height):
 		self.set_sample_rate(2.4)
 		self.set_gain('AUTO')
 
+        def close_sdr(self):
+            self.sdr.close()
+
+        def open_sdr(self):
+            self.sdr.close()
+            time.sleep(1)
+            self.sdr.open()
+
 	def _clear_intensity(self):
 		if self.min_auto_scale:
 			self.min_intensity = None
@@ -59,7 +67,7 @@ def get_center_freq(self):
 		return self.sdr.get_center_freq()/1000000.0
 
 	def set_center_freq(self, freq_mhz):
-		"""Set tuner center frequency to provided megahertz value."""
+                """Set tuner center frequency to provided megahertz value."""
 		try:
 			self.sdr.set_center_freq(freq_mhz*1000000.0)
 			self._clear_intensity()

views.py

@@ -265,7 +265,8 @@ def __init__(self, model, controller):
 		self.buttons.add(0, 2, gain_text,       colspan=4, click=self.gain_click)
 		self.buttons.add(0, 3, min_text,        colspan=2, click=self.min_click)
 		self.buttons.add(2, 3, max_text,        colspan=2, click=self.max_click)
-		self.buttons.add(0, 4, 'BACK', click=self.controller.change_to_main)
+		self.buttons.add(0, 4, 'Demodulation', colspan=2, click=self.controller.demodulate)
+		self.buttons.add(2, 4, 'BACK', colspan=2, click=self.controller.change_to_main)
 
 	def render(self, screen):
 		# Clear view and render buttons.
@@ -339,6 +340,7 @@ def __init__(self, model, controller):
 		self.buttons.add(3, 0, 'QUIT', click=self.quit_click,
 			bg_color=freqshow.CANCEL_BG)
 		self.overlay_enabled = True
+                model.open_sdr()
 
 	def render_spectrogram(self, screen):
 		"""Subclass should implement spectorgram rendering in the provided