main script

import time
import datetime
import paho.mqtt.client as mqtt
import ssl
import json
import _thread
import RPi.GPIO as GPIO
 
#GPIO Mode (BOARD / BCM)
GPIO.setmode(GPIO.BCM)
 
#set GPIO Pins
GPIO_TRIGGER = 18
GPIO_ECHO = 24
 
#set GPIO direction (IN / OUT)
GPIO.setup(GPIO_TRIGGER, GPIO.OUT)
GPIO.setup(GPIO_ECHO, GPIO.IN)

def on_connect(client, userdata, flags, rc):
    print("Connected to AWS IoT: " + str(rc))

client = mqtt.Client()
client.on_connect = on_connect
client.tls_set(ca_certs='./rootCA.pem', certfile='./certificate.pem.crt', keyfile='./private.pem.key', tls_version=ssl.PROTOCOL_SSLv23)
client.tls_insecure_set(True)
client.connect("YOUR_ENDPOINT_HERE", 8883, 60)

def publishData(txt):
    print(txt)

    while (True):
        # set Trigger to HIGH
        GPIO.output(GPIO_TRIGGER, True)
    
        # set Trigger after 0.01ms to LOW
        time.sleep(0.00001)
        GPIO.output(GPIO_TRIGGER, False)
    
        StartTime = time.time()
        StopTime = time.time()
    
        # save StartTime
        while GPIO.input(GPIO_ECHO) == 0:
            StartTime = time.time()
    
        # save time of arrival
        while GPIO.input(GPIO_ECHO) == 1:
            StopTime = time.time()
    
        # time difference between start and arrival
        TimeElapsed = StopTime - StartTime
        # multiply with the sonic speed (34300 cm/s)
        # and divide by 2, because there and back
        distance = (TimeElapsed * 34300) / 2

        print ("Measured Distance = %.1f cm" % distance)

        status = ""
        if distance >= 25:
            status = "GREEN"
        elif distance <= 24 and distance >= 10:
            status = "YELLOW"
        else:
            status = "RED"

        timestamp = datetime.datetime.now().strftime("%m/%d/%Y, %H:%M:%S")

        #client.publish("raspi/data", payload=json.dumps({"distance": distance}), qos=0, retain=False)
        client.publish("raspi/data", payload=json.dumps({"timestamp": timestamp, "distance": distance, "status": status}), qos=0, retain=False)

        time.sleep(5)
 
_thread.start_new_thread(publishData,("Spin-up new Thread...",))

client.loop_forever()