Source Code for Module UltrasonicSensor

  1  # UltrasonicSensor.java 
  2   
  3  ''' 
  4  Class that represents an ultrasonic sensor. 
  5   
  6   This software is part of the raspibrick module. 
  7   It is Open Source Free Software, so you may 
  8   - run the code for any purpose 
  9   - study how the code works and adapt it to your needs 
 10   - integrate all or parts of the code in your own programs 
 11   - redistribute copies of the code777 
 12   - improve the code and release your improvements to the public 
 13   However the use of the code is entirely your responsibility. 
 14   ''' 
 15   
 16  import SharedConstants 
 17  from RobotInstance import RobotInstance 
 18  from Tools import Tools 
 19  import RPi.GPIO as GPIO 
 20  import time 
 21   
 22 -class UltrasonicSensor(): 
 23      ''' 
 24      Class that represents an ultrasonic sensor. 
 25      ''' 
 26 -    def __init__(self, **kwargs): 
 27          ''' 
 28          Creates a sensor instance. 
 29          ''' 
 30          self.sensorState = "FAR" 
 31          self.sensorType = "UltrasonicSensor" 
 32          self.triggerLevel = 20 
 33          self.nearCallback = None 
 34          self.farCallback = None 
 35          for key in kwargs: 
 36              if key == "near": 
 37                  self.nearCallback = kwargs[key] 
 38              elif key == "far": 
 39                  self.farCallback = kwargs[key] 
 40          robot = RobotInstance.getRobot() 
 41          if robot == None:  # deferred registering, because Robot not yet created 
 42              RobotInstance._sensorsToRegister.append(self) 
 43          else: 
 44              if self.nearCallback != None or self.farCallback != None: 
 45                  robot.registerSensor(self) 
 46          Tools.debug("UltrasonicSensor instance created") 
 47   
 48 -    def getValue(self): 
 49          ''' 
 50          Returns the distance. 
 51          @return: Distance from target in cm, or -1 if no object or error 
 52          @rtype: float 
 53          ''' 
 54          self._checkRobot() 
 55          # Set pins as output and input 
 56          GPIO.setup(SharedConstants.P_TRIG_ECHO, GPIO.OUT) 
 57          GPIO.output(SharedConstants.P_TRIG_ECHO, GPIO.LOW) 
 58   
 59          # Allow module to settle 
 60          time.sleep(0.1) 
 61   
 62          # Send max 10 us trigger pulse 
 63          GPIO.output(SharedConstants.P_TRIG_ECHO, GPIO.HIGH) 
 64          time.sleep(0.00001) 
 65          GPIO.output(SharedConstants.P_TRIG_ECHO, GPIO.LOW) 
 66   
 67          # Prepare for echo 
 68          GPIO.setup(SharedConstants.P_TRIG_ECHO, GPIO.IN) 
 69   
 70          # Determine echo pulse length 
 71          start = time.time() 
 72          count = start 
 73   
 74          # Wait max 1 s for HIGH signal 
 75          while GPIO.input(SharedConstants.P_TRIG_ECHO) == GPIO.LOW and count - start < 1: 
 76              count = time.time() 
 77          if count - start >= 1: 
 78              Tools.debug("Timeout while waiting for echo going HIGH") 
 79              return -1 # error 
 80   
 81          # Wait  for LOW signal 
 82          elapsed = 0 
 83          while GPIO.input(SharedConstants.P_TRIG_ECHO) == GPIO.HIGH: 
 84              elapsed = time.time() - start 
 85              if elapsed > 0.015:  # echo considered as failed (distance too big) 
 86                  break 
 87   
 88          # Distance = speed_of_sound * elapsed / 2 
 89          distance =  34300 * elapsed / 2.0 
 90          # round to 2 decimals 
 91          distance = int(distance * 100 + 0.5) / 100.0 
 92          return distance 
 93   
 94 -    def getDistance(self): 
 95          ''' 
 96          Returns the distance. 
 97          @return: Distance from target in cm formatted to two decimals, or -1 if no object or error 
 98          @rtype: str 
 99          ''' 
100          return format(self.getValue(), ".2f") 
101   
102 -    def getTriggerLevel(self): 
103          return self.triggerLevel 
104   
105 -    def setTriggerLevel(self, level): 
106          self.triggerLevel = level 
107   
108 -    def getSensorState(self): 
109          return self.sensorState 
110   
111 -    def setSensorState(self, state): 
112          self.sensorState = state 
113   
114 -    def getSensorType(self): 
115          return self.sensorType 
116   
117 -    def onNear(self, v): 
118          if self.nearCallback != None: 
119              self.nearCallback(v) 
120   
121 -    def onFar(self, v): 
122          if self.farCallback != None: 
123              self.farCallback(v) 
124   
125 -    def _checkRobot(self): 
126          if RobotInstance.getRobot() == None: 
127              raise Exception("Create Robot instance first") 
128