from umqtt.simple import MQTTClient  # Import MQTT client library
import network  # Import network library for WiFi connection
import machine, time

# Initialize pins
trigger = machine.Pin(5, machine.Pin.OUT)
echo = machine.Pin(18, machine.Pin.IN)

# WiFi credentials
ssid = 'Wokwi-GUEST'  # Your WiFi SSID
password = ''  # Your WiFi password

# ThingSpeak MQTT settings
mqtt_server = "mqtt3.thingspeak.com"  # ThingSpeak MQTT server address
channel_id = "2495162"  # Your ThingSpeak Channel ID
write_api_key = "KSJFGA0HWGPVZYOS"  # Your ThingSpeak channel write API key
client_id = "HQ47ExsZMwwNITA5AgwzCTs"  # Client ID for MQTT connection (can be empty)
mqtt_user = "HQ47ExsZMwwNITA5AgwzCTs"
mqtt_password = "Iotf27skR4Lp6yxZLR9v/mPu"

# Connect to WiFi
station = network.WLAN(network.STA_IF)  # Create a station interface for WiFi connection
station.active(True)  # Activate the station interface
station.connect(ssid, password)  # Connect to the WiFi network
while station.isconnected() == False:  # Wait until the connection is successful
    pass
print("Connection successful")

def measure_distance():
    trigger.value(0)  # Set trigger low
    time.sleep_us(2)  # Settle the sensor
    trigger.value(1)  # Set trigger high
    time.sleep_us(10)  # Send out an ultrasonic pulse
    trigger.value(0)
    
    while echo.value() == 0:
        signal_off = time.ticks_us()
    while echo.value() == 1:
        signal_on = time.ticks_us()
        
    time_passed = signal_on - signal_off
    distance = (time_passed * 0.0343) / 2
    
    return distance

def send_to_thingspeak(distance):
    client = MQTTClient(client_id, mqtt_server, user=mqtt_user, password=mqtt_password)
    client.connect()  # Connect to the MQTT server
    client.publish("channels/2495162/publish/fields/field1", str(distance))  # Publish payload to the specified channel
    client.disconnect()  # Disconnect from the MQTT server

while True:
    distance = measure_distance()  # Measure distance using the ultrasonic sensor
    send_to_thingspeak(distance)  # Send the measured distance to ThingSpeak
    print("Sent distance:", distance, "to ThingSpeak")  # Print confirmation message
    time.sleep(5)  # Delay between posts due to ThingSpeak's rate limit