first re-commit.

pigpio-master/EXAMPLES/Python/SONAR_RANGER/sonar_trigger_echo.py

@@ -0,0 +1,114 @@
+#!/usr/bin/env python
+
+import time
+
+import pigpio
+
+class ranger:
+   """
+   This class encapsulates a type of acoustic ranger.  In particular
+   the type of ranger with separate trigger and echo pins.
+
+   A pulse on the trigger initiates the sonar ping and shortly
+   afterwards a sonar pulse is transmitted and the echo pin
+   goes high.  The echo pins stays high until a sonar echo is
+   received (or the response times-out).  The time between
+   the high and low edges indicates the sonar round trip time.
+   """
+
+   def __init__(self, pi, trigger, echo):
+      """
+      The class is instantiated with the Pi to use and the
+      gpios connected to the trigger and echo pins.
+      """
+      self.pi    = pi
+      self._trig = trigger
+      self._echo = echo
+
+      self._ping = False
+      self._high = None
+      self._time = None
+
+      self._triggered = False
+
+      self._trig_mode = pi.get_mode(self._trig)
+      self._echo_mode = pi.get_mode(self._echo)
+
+      pi.set_mode(self._trig, pigpio.OUTPUT)
+      pi.set_mode(self._echo, pigpio.INPUT)
+
+      self._cb = pi.callback(self._trig, pigpio.EITHER_EDGE, self._cbf)
+      self._cb = pi.callback(self._echo, pigpio.EITHER_EDGE, self._cbf)
+
+      self._inited = True
+
+   def _cbf(self, gpio, level, tick):
+      if gpio == self._trig:
+         if level == 0: # trigger sent
+            self._triggered = True
+            self._high = None
+      else:
+         if self._triggered:
+            if level == 1:
+               self._high = tick
+            else:
+               if self._high is not None:
+                  self._time = tick - self._high
+                  self._high = None
+                  self._ping = True
+
+   def read(self):
+      """
+      Triggers a reading.  The returned reading is the number
+      of microseconds for the sonar round-trip.
+
+      round trip cms = round trip time / 1000000.0 * 34030
+      """
+      if self._inited:
+         self._ping = False
+         self.pi.gpio_trigger(self._trig)
+         start = time.time()
+         while not self._ping:
+            if (time.time()-start) > 5.0:
+               return 20000
+            time.sleep(0.001)
+         return self._time
+      else:
+         return None
+
+   def cancel(self):
+      """
+      Cancels the ranger and returns the gpios to their
+      original mode.
+      """
+      if self._inited:
+         self._inited = False
+         self._cb.cancel()
+         self.pi.set_mode(self._trig, self._trig_mode)
+         self.pi.set_mode(self._echo, self._echo_mode)
+
+if __name__ == "__main__":
+
+   import time
+
+   import pigpio
+
+   import sonar_trigger_echo
+
+   pi = pigpio.pi()
+
+   sonar = sonar_trigger_echo.ranger(pi, 23, 18)
+
+   end = time.time() + 600.0
+
+   r = 1
+   while time.time() < end:
+
+      print("{} {}".format(r, sonar.read()))
+      r += 1
+      time.sleep(0.03)
+
+   sonar.cancel()
+
+   pi.stop()
+