print("This is the program for Car Reverse Sensor System")
print("By JOE for Iot Class)")

#STEP 1: IMPORT MODULES OR LIBRARY 
import hcsr04 # import ultrasonic library
import ssd1306 # import oled library
from machine import Soft12C, PWM, Pin 
from time import sleep

#STEP 2 : DECLARE CONNECTION
#STEP 2.1 :DECLRE CONNECTION FOR ULTRASONIC
ultrasonic_sensor=hcsr04.HCSR04(trigger_pin=5,echo_pin=18,echo_timeout_us=500*2*30)

#STEP2.2 : DECLRE THE  CONNECTION FOR OLED
i2c_oleddisplay = SoftI2C(scl=Pin(22), sda=Pin(21))
oled_width = 128 
oled_height = 64 
oled=ssd1306.SSD1306_I2C(oled_width,oled_height,i2c_oleddisplay)

#STEP2.3 : DECLARE THE CONNECTION OF BUZZER
buzzer = PWM(Pin(23),Pin.OUT)

#STEP 3: THE PROCESS

while True:
    #for ultrasonic sensor on the terminal
    distance_in_cm= ultrasonic_sensor.distance_cm()
    distance_in_mm= ultrasonic_sensor.distance_mm()

    print('An object is detected in : ',distance_in_cm, 'cm')
    print('An object is detected in : ',distance_in_mm, 'mm')

    #to display the distance on OLED
    oled.fill(1) # 1 means line number 1
    oled.text('Object detected: ',3,0,0)
    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('mm',75,40,0)
    oled.show()

    #check the range <50
    if distance_in_cm<50
        for i in range(100):
            buzzer.init(freq=1400,duty=400)
            sleep(0.5)
            buzzer.init(freq=1,duty=0)
            sleep(0.5)

    elif distance_in_cm<150
     for i in range(100):
            buzzer.init(freq=1400,duty=400)
            sleep(1)
            buzzer.init(freq=1,duty=0)
            sleep(1)
    
    else:
        buzzer.init(freq=1,duty=0)

    sleep(5)