print ("Reverse parking sensor")

#import modules/ library

import hcsr04 #ultrasonic sensor
import ssd1306 #import oled
from machine import SoftI2C,Pin,PWM #PWM=pulse width modulation 
from time import sleep

#ultrasonic sensor 

ultrasonic sensor= hcsr04.HCSR04(trigger_pin=13,echo_pin=27,echo_timeout_us=500*2*30)

#OLED set up
i2c_oleddisplay=SoftI2C(scl=Pin(22),sda=Pin(21))
oled_width=128
oled_height=64

#use OOP to create the project
oled=ssd1306.SSD1306_I2C(oled_width,oled_height,i2c_oleddisplay)

#buzzer, declare/create the connection
buzzer=PWM(Pin(23,Pin.OUT))

#test ultrasonic sensor,buzzer and OLED

while True:
    distance_in_cm=ultrasonic_sensor.distance_cm
    distance_in_mm=ultrasonic_sensor.distance_in_mm

    print('An object is detected within: ',distance_in_mm)

    #to display the distance on OLED
    oled.fill(1)
    oled.text('Object"',3,0,0) #the 1st 0 is X axis, 2nd 0 is Y axis
    oled.text(str( distance_in_cm),5,20,0) 
    oled, text ('cm', 75,20,0)
     oled.text(str( distance_in_mm), 5,40,0)
    oled. text ('cm', 75,40,0)
    oled.show()
    
    # to determine the distance 50cm or 150cm
    if distance_in_cm<50:
        for 1 in range(10):
            buzzer.init (freq=1703, duty=400)
            sleep(0.5)
            buzzer, init(freq=1, duty=400)
            sleep(0.5)

    elif 50 <= distance in cm <150 :
        for i in range(10):
            buzzer, init (freq-1703, duty=400)I
            sleep(0.5)
            buzzer.init(freq=1, duty=400)
            sleep(1)

    else:
        buzzer.init(freq=1, duty=0)
    sleep(5)