import network
import time
import machine
from machine import Pin
import ujson
from time import sleep_us,sleep
from umqtt.simple import MQTTClient

# MQTT Server Parameters
MQTT_CLIENT_ID = "2023PJ16029"   # Employee ID Lagnesh Sharma
MQTT_BROKER    = "test.mosquitto.org"   #MQTT Protocol
MQTT_USER      = ""
MQTT_PASSWORD  = ""
MQTT_TOPIC     = "/IIoT/2023PJ16029/distance"   #MQTT Topic name

trig=Pin(5,Pin.OUT)        
echo=Pin(18,Pin.IN)        

print("Connecting to WiFi", end="")
sta_if = network.WLAN(network.STA_IF)
sta_if.active(True)
sta_if.connect('Wokwi-GUEST', '')
while not sta_if.isconnected():
  print(".", end="")
  time.sleep(0.1)
print(" Connected!")

print("Connecting to MQTT server... ", end="")
client = MQTTClient(MQTT_CLIENT_ID, MQTT_BROKER, user=MQTT_USER, password=MQTT_PASSWORD)
client.connect()

print("Connected!")

prev_mes=""
Distance=0
pulseduration=0
while True:
  trig.off()
  sleep_us(5)
  trig.on()
  sleep_us(10)
  trig.off()
  
  pulseduration=machine.time_pulse_us(echo, 1, 30000) #Pulse duration 
  print(pulseduration)
  Distance=((0.034*(pulseduration))/2) 
  #Distance from an object = ((speed of sound in air * pulseduration)/2)
  #Speed of sound in air at 20 dec celcius is 343 m/sec
  print("value of distance ", end="")
  
  message = ujson.dumps({
  "Dist": Distance,
    
  })
  if message != prev_mes:
    print("Updated!")
    print("Reporting to MQTT topic {}".format(message))
    client.publish(MQTT_TOPIC, message)
    prev_mes=message
  else:
    print("No change")
  time.sleep(1)