The sample code for ultrasonic sensor with Raspberry Pi Pico

UltrasonicPico.py

from machine import Pin, PWM
import utime

Trig = Pin(27, Pin.OUT)
Echo = Pin(26, Pin.IN, Pin.PULL_DOWN)

Buzzer = PWM(Pin(18))

def CheckDistance():
    SpeedOfSoundInCM = 0.034
    Trig.low()
    utime.sleep_us(2)
    Trig.high()
    utime.sleep_us(10)
    Trig.low()
    exitLoop = False
    loopcount = 0 #used as a failsafe if the signal doesn't return
    while Echo.value() == 0 and exitLoop == False:
        loopcount = loopcount + 1
        delaytime = utime.ticks_us()
        
        if loopcount > 3000 : exitLoop == True
    
    while Echo.value() == 1 and exitLoop == False:
        loopcount = loopcount + 1
        receivetime = utime.ticks_us()
        if loopcount > 3000 : exitLoop == True
    
    if exitLoop == True: #We failed somewhere
        return 0
    else:
        distance = ((receivetime - delaytime) * SpeedOfSoundInCM) / 2
        return distance

while True:
    distance = CheckDistance()
    print(distance)
    if CheckDistance() < 10:
        Buzzer.duty_u16(3000)
        Buzzer.freq(1700)
        utime.sleep(0.05)
        Buzzer.duty_u16(0)
        utime.sleep(CheckDistance() / 1000)