View difference between Paste ID: VpcLebzD and RbDjLFjM

 # maxSonarTTY.py
 
 import serial
 import re
 
 class MaxSonar( serial.Serial ):
     def __init__( self, port ):
         super().__init__( port=port, baudrate=9600, timeout=0.5 )
 
     def measure( self ):
         self.reset_input_buffer()
 
-        data = self.read_until( b'\r', size=5 )
+        data = self.read_until( expected=b'\r', size=5 )
 
         if re.fullmatch( rb'\d*\r', data ):
             # partial line received, wait for next one
-            data = self.read_until( b'\r', size=5 )
+            data = self.read_until( expected=b'\r', size=5 )
 
         if len( data ) < 5 and not data.endswith( b'\r' ):
             raise RuntimeError( "Timeout while waiting for data" )
 
-        m = re.fullmatch( rb'R(\d+)\r', data )
+        m = re.fullmatch( rb'R(0|[1-9]\d*)\r', data )
         if not m:
             raise RuntimeError( "Garbage data received: %r" % data )
         data = m.group( 1 )
 
         return int( data )  # measurement in inches (0-255)
 
 
 # maxSonarTTY-example.py
 
 from time import sleep
 from maxSonarTTY import MaxSonar
 
 sonar = MaxSonar( "/dev/ttyS2" )
 
 try:
     while True:
         distance = sonar.measure()
         print( "distance =", distance, "inch" )
 
         sleep( 1 )
 
 except KeyboardInterrupt:
     pass