7.10 Reversing Aid

This project uses an LED, a buzzer and an ultrasonic module to create a reversing assist system. We can put it on a remote control car to simulate the the actual process of reversing a car into a garage.

Schematic

sch_reversing_aid

Wiring

wiring_reversing_aid

Code

Note

  • Open the 7.10_reversing_aid.py file under the path of kepler-kit-main/micropython or copy this code into Thonny, then click “Run Current Script” or simply press F5 to run it.

  • Don’t forget to click on the “MicroPython (Raspberry Pi Pico)” interpreter in the bottom right corner.

  • For detailed tutorials, please refer to Open and Run Code Directly.

import machine
import time
import _thread


buzzer = machine.Pin(15, machine.Pin.OUT)
led = machine.Pin(14, machine.Pin.OUT)

TRIG = machine.Pin(17,machine.Pin.OUT)
ECHO = machine.Pin(16,machine.Pin.IN)

dis = 100

def distance():
    timeout=10000*5/340
    TRIG.low()
    time.sleep_us(2)
    TRIG.high()
    time.sleep_us(10)
    TRIG.low()
    timeout_start = time.ticks_ms() # For timeout, re-read distance
    while not ECHO.value():
        waiting_time = time.ticks_ms()
        if waiting_time - timeout_start > timeout:
            return -1
    time1 = time.ticks_us()
    while ECHO.value():
        waiting_time = time.ticks_ms()
        if waiting_time - timeout_start > timeout:
            return -1
    time2 = time.ticks_us()
    during = time.ticks_diff(time2 ,time1)
    return during * 340 / 2 / 10000

def ultrasonic_thread():
    global dis
    while True:
        dis = distance()

_thread.start_new_thread(ultrasonic_thread, ())

def beep():
    buzzer.value(1)
    led.value(1)
    time.sleep(0.1)
    buzzer.value(0)
    led.value(0)
    time.sleep(0.1)

intervals = 10000000
previousMills=time.ticks_ms()
time.sleep(1)

while True:
    if dis<0:
        pass
    elif dis <= 10:
        intervals = 300
    elif dis <= 20:
        intervals =500
    elif dis <=50:
        intervals =1000
    else:
        intervals = 2000
    if dis!=-1:
        print ('Distance: %.2f' % dis)
        time.sleep_ms(100)


    currentMills=time.ticks_ms()

    if time.ticks_diff(currentMills,previousMills)>=intervals:
        beep()
        previousMills=currentMills
  • As soon as the program runs, the ultrasonic sensor will continuously read the distance to the obstacle in front of you, and you will be able to see the exact distance value on the shell.

  • The LED and buzzer will change the frequency of blinking and beeping depending on the distance value, thus indicating the approach of the obstacle.

  • The 6.1 Measuring Distance article mentioned that when the ultrasonic sensor works, the program will be paused.

  • To avoid interfering with the LED or buzzer timing, we created a separate thread for ranging in this example.