kopia lustrzana https://github.com/GuyCarver/MicroPython
72 wiersze
1.6 KiB
Python
72 wiersze
1.6 KiB
Python
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from pyb import Pin, Timer, udelay
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# WARNING: Do not use PA4-X5 or PA5-X6 as the echo pin without a 1k resistor.
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class SR04Distance(object):
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""" """
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maxinches = 20 #maximum range of SR04.
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def __init__( self, tpin, epin, timer=2 ) :
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""" """
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if type(tpin) == str:
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self._tpin = Pin(tpin, Pin.OUT_PP, Pin.PULL_NONE)
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elif type(tpin) == Pin:
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self._tpin = tpin
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else:
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raise Exception("trigger pin must be pin name or pyb.Pin configured for output.")
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self._tpin.low()
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if type(epin) == str:
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self._epin = Pin(epin, Pin.IN, Pin.PULL_NONE)
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elif type(epin) == Pin:
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self._epin = epin
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else:
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raise Exception("echo pin must be pin name or pyb.Pin configured for input.")
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# Create a microseconds counter.
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self._micros = Timer(timer, prescaler=83, period=0x3fffffff)
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def __del__( self ) :
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self._micros.deinit()
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@property
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def counter( self ) : return self._micros.counter()
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@counter.setter
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def counter( self, value ) : self._micros.counter(value)
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@property
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def centimeters( self ) :
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start = 0
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end = 0
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self.counter = 0
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#Send 10us pulse.
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self._tpin.high()
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udelay(10)
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self._tpin.low()
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while not self._epin.value():
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start = self.counter
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j = 0
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# Wait 'till the pulse is gone.
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while self._epin.value() and j < 1000:
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j += 1
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end = self.counter
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# Calc the duration of the recieved pulse, divide the result by
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# 2 (round-trip) and divide it by 29 (the speed of sound is
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# 340 m/s and that is 29 us/cm).
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return (end - start) / 58
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@property
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def inches( self ) : return self.centimeters * 0.3937
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