Ultrasonic Sensor HC-SR04

Description

The HC-SR04 is an ultrasonic distance sensor that can measure distances from 2cm to 400cm. It sends out an ultrasound signal and detects the echo. By measuring the time you can calculate the distance.

more details:

• https://randomnerdtutorials.com/complete-guide-for-ultrasonic-sensor-hc-sr04/
• https://cdn.sparkfun.com/datasheets/Sensors/Proximity/HCSR04.pdf

How to connect it electrically

Required Module and Files

• We use hcsr04.py
• this is downloaded from https://github.com/rsc1975/micropython-hcsr04
• the original file is at https://github.com/rsc1975/micropython-hcsr04/blob/master/hcsr04.py

How to control it in MicroPython

from hcsr04 import HCSR04
from time import sleep

sensor = HCSR04(trigger_pin=12, echo_pin=14)
sleep(1)
i=0

while True:
  distance = sensor.distance_cm()
  print(i, ': Distance:', distance, 'cm')
  i=i+1
  sleep(0.5)

Background

connecting it to the ESP8266 and reading the signal in without a library/module.

Connect Trig to Pin5 and Echo to Pin4 of the ESP8266.

import machine
import utime


while True:
  trig=machine.Pin(5, machine.Pin.OUT)
  trig.off()
  utime.sleep_us(2)
  trig.on()
  utime.sleep_us(10)
  trig.off()
  echo=machine.Pin(4, machine.Pin.IN)
  while echo.value() == 0:
    pass
  t1 = utime.ticks_us()
  while echo.value() == 1:
    pass
  t2 = utime.ticks_us()
  cm = (t2 - t1) / 58.0
  print(cm)
  utime.sleep(2)