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| − | == Code for RP2040 (with the library in the main code) ==
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| − |
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| − | This is the version for the Arduino Nano Connect RP2040 using GPIO25 as trigger_pin and GPIO15 as echo_pin.
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| − |
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| − | <syntaxhighlight lang="python" line='line'>
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| − |
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| − | import machine, time
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| − | from machine import Pin
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| − |
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| − | #acknowlegement for the library
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| − | __version__ = '0.2.0'
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| − | __author__ = 'Roberto Sánchez'
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| − | __license__ = "Apache License 2.0. https://www.apache.org/licenses/LICENSE-2.0"
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| − |
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| − | class HCSR04:
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| − | """
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| − | Driver to use the untrasonic sensor HC-SR04.
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| − | The sensor range is between 2cm and 4m.
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| − |
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| − | The timeouts received listening to echo pin are converted to OSError('Out of range')
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| − |
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| − | """
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| − | # echo_timeout_us is based in chip range limit (400cm)
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| − | def __init__(self, trigger_pin, echo_pin, echo_timeout_us=500*2*30):
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| − | """
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| − | trigger_pin: Output pin to send pulses
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| − | echo_pin: Readonly pin to measure the distance. The pin should be protected with 1k resistor
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| − | echo_timeout_us: Timeout in microseconds to listen to echo pin.
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| − | By default is based in sensor limit range (4m)
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| − | """
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| − | self.echo_timeout_us = echo_timeout_us
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| − | # Init trigger pin (out)
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| − | self.trigger = Pin(trigger_pin, mode=Pin.OUT, pull=None)
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| − | self.trigger.value(0)
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| − |
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| − | # Init echo pin (in)
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| − | self.echo = Pin(echo_pin, mode=Pin.IN, pull=None)
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| − |
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| − | def _send_pulse_and_wait(self):
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| − | """
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| − | Send the pulse to trigger and listen on echo pin.
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| − | We use the method `machine.time_pulse_us()` to get the microseconds until the echo is received.
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| − | """
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| − | self.trigger.value(0) # Stabilize the sensor
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| − | time.sleep_us(5)
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| − | self.trigger.value(1)
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| − | # Send a 10us pulse.
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| − | time.sleep_us(10)
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| − | self.trigger.value(0)
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| − | try:
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| − | pulse_time = machine.time_pulse_us(self.echo, 1, self.echo_timeout_us)
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| − | return pulse_time
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| − | except OSError as ex:
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| − | if ex.args[0] == 110: # 110 = ETIMEDOUT
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| − | raise OSError('Out of range')
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| − | raise ex
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| − |
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| − | def distance_mm(self):
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| − | """
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| − | Get the distance in milimeters without floating point operations.
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| − | """
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| − | pulse_time = self._send_pulse_and_wait()
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| − |
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| − | # To calculate the distance we get the pulse_time and divide it by 2
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| − | # (the pulse walk the distance twice) and by 29.1 becasue
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| − | # the sound speed on air (343.2 m/s), that It's equivalent to
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| − | # 0.34320 mm/us that is 1mm each 2.91us
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| − | # pulse_time // 2 // 2.91 -> pulse_time // 5.82 -> pulse_time * 100 // 582
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| − | mm = pulse_time * 100 // 582
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| − | return mm
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| − |
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| − | def distance_cm(self):
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| − | """
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| − | Get the distance in centimeters with floating point operations.
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| − | It returns a float
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| − | """
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| − | pulse_time = self._send_pulse_and_wait()
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| − |
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| − | # To calculate the distance we get the pulse_time and divide it by 2
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| − | # (the pulse walk the distance twice) and by 29.1 becasue
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| − | # the sound speed on air (343.2 m/s), that It's equivalent to
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| − | # 0.034320 cm/us that is 1cm each 29.1us
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| − | cms = (pulse_time / 2) / 29.1
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| − | return cms
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| − |
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| − |
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| − | # contributed at the UBISS2024 Seminar
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| − |
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| − | from time import sleep
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| − | sensor = HCSR04(trigger_pin=25, echo_pin=15)
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| − | sleep(1)
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| − | i=0
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| − |
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| − |
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| − | while True:
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| − | distance = sensor.distance_cm()
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| − | print(i, ': Distance:', distance, 'cm')
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| − | i=i+1
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| − | sleep(0.5)
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| − |
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| − | </syntaxhighlight>
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| | [[Category:Sensor]] | | [[Category:Sensor]] |
