Note

Hello, welcome to the SunFounder Raspberry Pi & Arduino & ESP32 Enthusiasts Community on Facebook! Dive deeper into Raspberry Pi, Arduino, and ESP32 with fellow enthusiasts.

Why Join?

Expert Support: Solve post-sale issues and technical challenges with help from our community and team.
Learn & Share: Exchange tips and tutorials to enhance your skills.
Exclusive Previews: Get early access to new product announcements and sneak peeks.
Special Discounts: Enjoy exclusive discounts on our newest products.
Festive Promotions and Giveaways: Take part in giveaways and holiday promotions.

👉 Ready to explore and create with us? Click [here] and join today!

Lesson 23: Ultrasonic Sensor Module (HC-SR04)

In this lesson, you will learn how to measure distances using the Raspberry Pi Pico W and an HC-SR04 ultrasonic sensor. You’ll find out how to connect the sensor to the Pico W and write a MicroPython script to control it. The lesson will cover calculating distances based on the time it takes for ultrasonic waves to reflect back from objects. This practical project provides insights into working with sensors, handling digital signals, and basic calculations in MicroPython, suitable for those interested in hardware interfacing with the Raspberry Pi Pico W.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
Raspberry Pi Pico W	BUY
Ultrasonic Sensor Module (HC-SR04)	BUY
Breadboard	BUY

Wiring

../_images/Lesson_23_ultrasonic_sensor_bb.png

Code

import machine  # Import machine module for hardware control
import time  # Import time module for delays

# Define pin numbers for ultrasonic sensor's TRIG and ECHO pins
TRIG = machine.Pin(17, machine.Pin.OUT)  # TRIG pin set as output
ECHO = machine.Pin(16, machine.Pin.IN)  # ECHO pin set as input


def distance():
    # Function to calculate distance in centimeters
    TRIG.low()  # Set TRIG low
    time.sleep_us(2)  # Wait for 2 microseconds
    TRIG.high()  # Set TRIG high
    time.sleep_us(10)  # Wait for 10 microseconds
    TRIG.low()  # Set TRIG low again

    # Wait for ECHO pin to go high
    while not ECHO.value():
        pass

    time1 = time.ticks_us()  # Record time when ECHO goes high

    # Wait for ECHO pin to go low
    while ECHO.value():
        pass

    time2 = time.ticks_us()  # Record time when ECHO goes low

    # Calculate the duration of the ECHO pin being high
    during = time.ticks_diff(time2, time1)

    # Return the calculated distance (using speed of sound)
    return during * 340 / 2 / 10000  # Distance in centimeters


# Main loop
while True:
    dis = distance()  # Get distance from sensor
    print("Distance: %.2f cm" % dis)  # Print distance
    time.sleep_ms(300)  # Wait for 300 milliseconds before next measurement

Code Analysis

Importing libraries

The machine and time modules are imported for accessing hardware-specific functions and time-related functions, respectively.
```
import machine
import time
```
Pin setup for HC-SR04

Two GPIO pins are defined for the HC-SR04 sensor: TRIG is an output pin to trigger the ultrasonic pulse, and ECHO is an input pin to receive the reflected pulse.
```
TRIG = machine.Pin(17, machine.Pin.OUT)
ECHO = machine.Pin(16, machine.Pin.IN)
```

Distance measurement function

The distance function triggers the ultrasonic pulse and calculates the distance based on the time taken for the echo to return. It uses time-based functions to measure the duration of the echo.

For more details, please refer to the working principle of the ultrasonic sensor module.

def distance():
    TRIG.low()
    time.sleep_us(2)
    TRIG.high()
    time.sleep_us(10)
    TRIG.low()

    while not ECHO.value():
        pass

    time1 = time.ticks_us()

    while ECHO.value():
        pass

    time2 = time.ticks_us()
    during = time.ticks_diff(time2, time1)
    return during * 340 / 2 / 10000

Main loop

The main loop continuously calls the distance function and prints the measured distance. It waits for 300 milliseconds between each measurement to prevent sensor saturation.
```
while True:
    dis = distance()
    print("Distance: %.2f cm" % dis)
    time.sleep_ms(300)
```