Added Reading data in chunks (#72)

Adds an example of periodically reading data in chunks

Author: spacemanspiff2007

documentation/shortintro.rst

@@ -87,3 +87,43 @@ port asynchronously::
     loop.run_forever()
     loop.close()
 
+Reading data in chunks
+----------------------
+
+This example will read chunks from the serial port every 300ms::
+
+
+    import asyncio
+    import serial_asyncio
+    
+    
+    class InputChunkProtocol(asyncio.Protocol):
+        def connection_made(self, transport):
+            self.transport = transport
+        
+        def data_received(self, data):
+            print('data received', repr(data))
+            
+            # stop callbacks again immediately
+            self.pause_reading()
+                
+        def pause_reading(self):
+            # This will stop the callbacks to data_received
+            self.transport.pause_reading()
+                
+        def resume_reading(self):
+            # This will start the callbacks to data_received again with all data that has been received in the meantime.
+            self.transport.resume_reading()
+        
+    
+    async def reader():
+        transport, protocol = await serial_asyncio.create_serial_connection(loop, InputChunkProtocol, '/dev/ttyUSB0', baudrate=115200)
+    
+        while True:
+            await asyncio.sleep(0.3)
+            protocol.resume_reading()
+    
+    
+    loop = asyncio.get_event_loop()
+    loop.run_until_complete(reader())
+    loop.close()