You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
79 lines
2.8 KiB
Python
79 lines
2.8 KiB
Python
import machine, time
|
|
from machine import Pin
|
|
|
|
__version__ = '0.2.0'
|
|
__author__ = 'Roberto Sánchez'
|
|
__license__ = "Apache License 2.0. https://www.apache.org/licenses/LICENSE-2.0"
|
|
|
|
class HCSR04:
|
|
"""
|
|
Driver to use the untrasonic sensor HC-SR04.
|
|
The sensor range is between 2cm and 4m.
|
|
|
|
The timeouts received listening to echo pin are converted to OSError('Out of range')
|
|
|
|
"""
|
|
# echo_timeout_us is based in chip range limit (400cm)
|
|
def __init__(self, trigger_pin, echo_pin, echo_timeout_us=500*2*30):
|
|
"""
|
|
trigger_pin: Output pin to send pulses
|
|
echo_pin: Readonly pin to measure the distance. The pin should be protected with 1k resistor
|
|
echo_timeout_us: Timeout in microseconds to listen to echo pin.
|
|
By default is based in sensor limit range (4m)
|
|
"""
|
|
self.echo_timeout_us = echo_timeout_us
|
|
# Init trigger pin (out)
|
|
self.trigger = Pin(trigger_pin, mode=Pin.OUT, pull=None)
|
|
self.trigger.value(0)
|
|
|
|
# Init echo pin (in)
|
|
self.echo = Pin(echo_pin, mode=Pin.IN, pull=None)
|
|
|
|
def _send_pulse_and_wait(self):
|
|
"""
|
|
Send the pulse to trigger and listen on echo pin.
|
|
We use the method `machine.time_pulse_us()` to get the microseconds until the echo is received.
|
|
"""
|
|
self.trigger.value(0) # Stabilize the sensor
|
|
time.sleep_us(5)
|
|
self.trigger.value(1)
|
|
# Send a 10us pulse.
|
|
time.sleep_us(10)
|
|
self.trigger.value(0)
|
|
try:
|
|
pulse_time = machine.time_pulse_us(self.echo, 1, self.echo_timeout_us)
|
|
return pulse_time
|
|
except OSError as ex:
|
|
if ex.args[0] == 110: # 110 = ETIMEDOUT
|
|
raise OSError('Out of range')
|
|
raise ex
|
|
|
|
def distance_mm(self):
|
|
"""
|
|
Get the distance in milimeters without floating point operations.
|
|
"""
|
|
pulse_time = self._send_pulse_and_wait()
|
|
|
|
# To calculate the distance we get the pulse_time and divide it by 2
|
|
# (the pulse walk the distance twice) and by 29.1 becasue
|
|
# the sound speed on air (343.2 m/s), that It's equivalent to
|
|
# 0.34320 mm/us that is 1mm each 2.91us
|
|
# pulse_time // 2 // 2.91 -> pulse_time // 5.82 -> pulse_time * 100 // 582
|
|
mm = pulse_time * 100 // 582
|
|
return mm
|
|
|
|
def distance_cm(self):
|
|
"""
|
|
Get the distance in centimeters with floating point operations.
|
|
It returns a float
|
|
"""
|
|
pulse_time = self._send_pulse_and_wait()
|
|
|
|
# To calculate the distance we get the pulse_time and divide it by 2
|
|
# (the pulse walk the distance twice) and by 29.1 becasue
|
|
# the sound speed on air (343.2 m/s), that It's equivalent to
|
|
# 0.034320 cm/us that is 1cm each 29.1us
|
|
cms = (pulse_time / 2) / 29.1
|
|
return cms
|
|
|