超音波センサーで距離測定してみた。

from machine import Timer, Pin
import time

# Define GPIO pin numbers for TRIG and ECHO
TRIG_PIN = 17  # TRIG connected to GPIO17
ECHO_PIN = 16  # ECHO connected to GPIO16

# Initialize TRIG and ECHO pins
TRIG = Pin(TRIG_PIN, Pin.OUT)  # Set TRIG pin as output
ECHO = Pin(ECHO_PIN, Pin.IN)   # Set ECHO pin as input

def distance():
    """
    Measures the distance using the HC-SR04 ultrasonic sensor.
    Returns:
        float: Distance in millimeters if successful
        -1: if measurement fails (timeout)
    """
    # Send a 10us pulse to trigger the ultrasonic burst
    TRIG.low()
    time.sleep_us(2)
    TRIG.high()
    time.sleep_us(10)
    TRIG.low()

    # Wait for ECHO to go HIGH (start of echo pulse)
    timeout_start = time.ticks_us()
    while not ECHO.value():
        if time.ticks_diff(time.ticks_us(), timeout_start) > 30000:
            return -1  # Timeout: no echo received

    # Record the start time of echo pulse
    time1 = time.ticks_us()

    # Wait for ECHO to go LOW (end of echo pulse)
    while ECHO.value():
        if time.ticks_diff(time.ticks_us(), time1) > 30000:
            return -1  # Timeout: echo pulse too long

    # Record the end time of echo pulse
    time2 = time.ticks_us()

    # Calculate the duration of the echo pulse
    duration = time.ticks_diff(time2, time1)

    # Calculate distance in millimeters
    # Speed of sound = 343 m/s = 343,000 mm/s
    # Divide by 2 since the pulse travels to and from the object
    distance_mm = duration * 343 / 2 / 1000

    return distance_mm

def measure_distance(timer):
    """
    Timer callback function that measures and prints the distance.
    """
    dis = distance()
    if dis != -1:
        print("Distance: %.0f mm" % dis)
    else:
        print("Measurement failed")

# Initialize a timer to call measure_distance() every 2 seconds
timer = Timer()
timer.init(period=2000, mode=Timer.PERIODIC, callback=measure_distance)

import machine
import time

# Define GPIO pins for the ultrasonic sensor
TRIG = machine.Pin(17, machine.Pin.OUT)  # TRIG pin (output)
ECHO = machine.Pin(16, machine.Pin.IN)   # ECHO pin (input)

def distance():
    """
    Measures distance using HC-SR04 with timeout protection.
    Returns:
        float: Distance in centimeters, or -1 if timeout occurs.
    """

    # Send a 10µs pulse to trigger the sensor
    TRIG.low()
    time.sleep_us(2)
    TRIG.high()
    time.sleep_us(10)
    TRIG.low()

    timeout_start = time.ticks_us()

    # Wait for ECHO to go HIGH (pulse starts)
    while not ECHO.value():
        if time.ticks_diff(time.ticks_us(), timeout_start) > 30000:
            return -1  # Timeout after 30 ms (no echo start)

    time1 = time.ticks_us()

    # Wait for ECHO to go LOW (pulse ends)
    while ECHO.value():
        if time.ticks_diff(time.ticks_us(), time1) > 30000:
            return -1  # Timeout after 30 ms (pulse too long)

    time2 = time.ticks_us()

    # Calculate pulse duration
    duration = time.ticks_diff(time2, time1)

    # Convert to distance in cm (speed of sound = 340 m/s)
    return duration * 340 / 2 / 1000  # distance in mm

# Main loop
while True:
    dis = distance()
    if dis != -1:
        print("Distance: %.0f mm" % dis)
    else:
        print("Measurement failed (timeout)")
    time.sleep_ms(1000)