# This MicroPython project on ESP32 simulates water analysis for a polluted river.
# It uses a potentiometer to simulate pH, an HC-SR04 ultrasonic sensor for water depth,
# and an NTC analog temperature sensor for temperature monitoring.
# It displays the values on an OLED screen and activates LEDs based on critical thresholds.
# A buzzer sounds if all three parameters reach critical values simultaneously.

from machine import Pin, ADC, PWM, I2C
from ssd1306 import SSD1306_I2C
from hcsr04 import HCSR04
from time import sleep

# ----------------------------
# Project: Polluted River Monitoring
# Features: pH, Water Depth, Temperature
# Outputs: OLED display, 3 LEDs, Buzzer if all are critical
# ----------------------------

# Import required libraries
from machine import Pin, ADC, PWM, I2C  # Hardware control: pins, analog/digital input/output, PWM, I2C
from ssd1306 import SSD1306_I2C         # OLED display driver
from hcsr04 import HCSR04               # Ultrasonic distance sensor driver
from time import sleep                  # Delay function

# -------------------------------
# OLED setup (128x64 display over I2C)
# SCL on pin 22, SDA on pin 21
# -------------------------------
i2c = I2C(0, scl=Pin(22), sda=Pin(21))           # Initialize I2C bus
oled = SSD1306_I2C(128, 64, i2c)                 # Create OLED object using the I2C bus

# -------------------------------
# Sensor setup
# -------------------------------
ph_sensor = ADC(Pin(34))                         # Simulated pH sensor using a potentiometer
ph_sensor.atten(ADC.ATTN_11DB)                   # Set ADC attenuation to read full 0–3.3V range

temp_sensor = ADC(Pin(35))                       # Temperature sensor using an analog NTC thermistor
temp_sensor.atten(ADC.ATTN_11DB)                 # Full range reading for accurate conversion

ultrasonic = HCSR04(trigger_pin=4, echo_pin=5)   # Ultrasonic sensor (HC-SR04) for water depth detection

# -------------------------------
# Output devices (LEDs and Buzzer)
# -------------------------------
led_ph = Pin(15, Pin.OUT)                        # Red LED for pH alert
led_depth = Pin(2, Pin.OUT)                      # Blue LED for low depth alert
led_temp = Pin(18, Pin.OUT)                      # Green LED for high temperature alert

buzzer = PWM(Pin(19), freq=1000)                 # Buzzer with PWM control (1kHz tone)
buzzer.duty(0)                                   # Start with buzzer OFF

# -------------------------------
# Threshold values for alerts
# -------------------------------
PH_CRITICAL = 9.0                                # If pH > 9.0, it's considered critical
DEPTH_LIMIT_CM = 5                               # If water depth < 5 cm, it's too shallow
TEMP_CRITICAL_C = 18.0                           # If temperature > 18°C, it's considered critical

# -------------------------------
# Function: Convert ADC to pH
# Returns pH value between 0 and 14
# -------------------------------
def read_ph():
    raw = ph_sensor.read()                       # Read analog value (0–4095)
    ph = (raw / 4095) * 14                       # Map raw value linearly to pH scale
    return round(ph, 2)                          # Round to 2 decimal places

# -------------------------------
# Function: Convert ADC to temperature
# Using a simplified linear approximation for NTC sensor
# -------------------------------
def read_temperature():
    raw = temp_sensor.read()                     # Read analog value (0–4095)
    temp = (raw / 4095) * 100                    # Approximate 0–100°C scale
    return round(temp, 1)                        # Round to 1 decimal place

# -------------------------------
# Function: Display sensor values on OLED
# Shows pH, depth, and temperature
# -------------------------------
def display(ph, depth, temp):
    oled.fill(0)                                 # Clear OLED screen
    oled.text("pH: {}".format(ph), 0, 0)         # Display pH value
    oled.text("Depth: {:.1f} cm".format(depth), 0, 20)  # Display depth in cm
    oled.text("Temp: {} C".format(temp), 0, 40)  # Display temperature in °C
    oled.show()                                  # Refresh the display

# -------------------------------
# Main program loop
# Continuously reads sensors, updates display,
# controls LEDs and buzzer based on thresholds
# -------------------------------
while True:
    ph_val = read_ph()                           # Get current pH value
    temp_val = read_temperature()                # Get current temperature

    try:
        depth_cm = ultrasonic.distance_cm()      # Measure water depth
    except OSError:
        depth_cm = -1                            # Set to -1 if sensor fails

    display(ph_val, depth_cm, temp_val)          # Show all values on OLED

    # -------------------------------
    # Control LEDs based on critical thresholds
    # Each LED turns ON if its condition is met
    # -------------------------------
    led_ph.value(ph_val > PH_CRITICAL)                               # Red LED on if pH is too high
    led_depth.value(depth_cm >= 0 and depth_cm < DEPTH_LIMIT_CM)     # Blue LED on if depth is too low
    led_temp.value(temp_val > TEMP_CRITICAL_C)                       # Green LED on if temp is too high

    # -------------------------------
    # Control buzzer: alert only if ALL three conditions are critical
    # -------------------------------
    if (ph_val > PH_CRITICAL and 
        depth_cm >= 0 and depth_cm < DEPTH_LIMIT_CM and 
        temp_val > TEMP_CRITICAL_C):
        buzzer.duty(512)                      # Turn buzzer ON
    else:
        buzzer.duty(0)                        # Turn buzzer OFF

    sleep(1)                                  # Wait 1 second before next loop