5. Detecting Distance

In this project, we will show you how to make the ultrasonic module detect the distance of the obstacle ahead.

The transmitting probe of the ultrasonic module emits high-frequency sound waves (ultrasonic waves), which are reflected back and detected by the receiving probe when they touch an object.

By calculating the time from the emission to the reception of ultrasonic waves, multiplied by the speed of sound, the distance of the obstacle can be obtained.

Code

import machine
import time

trig = machine.Pin(6,machine.Pin.OUT)
echo = machine.Pin(7,machine.Pin.IN)

def distance():
    # pulse
    trig.high()
    time.sleep_us(10)
    trig.low()

    # get time
    pulse_width_us = machine.time_pulse_us(echo, machine.Pin.on)
    pulse_width_s= pulse_width_us/ 1000000.0

    # calculate the distance
    distance_m = pulse_width_s * 340 / 2
    distance_cm = (distance_m *100)

    return distance_cm

while True:
    dis = distance()
    print ('Distance: %.2f' % dis)
    time.sleep_ms(300)

You can copy the above code into Thonny or open the sonar_5_get_distance.py under the path of pico_4wd_car-v2.0\examples\learn_modules. Then click the button or press F5 to run it.

After powering up the Pico 4WD, move the obstacle in front of it back and forth to verify the distance value (unit: cm).