MicroPython HC-SR04 distance with a driver file on an ESP32-DevKitC V4

# Ultrasonic ranging with a driver: sr04.py (its own tab) does the
# pulse and the timing, so the program only asks for the distance.
from sr04 import SR04
import time

sensor = SR04(13, 14)           # TRIG on GPIO 13, ECHO on GPIO 14

while True:
    cm = sensor.distance_cm()
    print("Distance: %.1f cm" % cm if cm is not None else "Out of range")
    time.sleep_ms(500)

# sr04.py: an HC-SR04 ultrasonic sensor, timed with time_pulse_us().
from machine import Pin, time_pulse_us
import time

class SR04:
    def __init__(self, trig, echo):
        self.trig = Pin(trig, Pin.OUT, value=0)
        self.echo = Pin(echo, Pin.IN)

    def distance_cm(self):
        self.trig.value(1)
        time.sleep_us(20)                          # 10 us or more starts a ping
        self.trig.value(0)
        us = time_pulse_us(self.echo, 1, 30000)   # how long ECHO is high
        if us < 0:
            return None                            # no echo: nothing in range
        return us * 0.0343 / 2