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#!/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()
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