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