from machine import I2C, Pin, ADC
from lcd_api import LcdApi
from pico_i2c_lcd import I2cLcd
import time
from math import log

#Defining Pin numbers
I2C_ADDR = 0x27                      #I2C address for LCD
THERMISTOR_PIN = 27                  #ADC pin for temperature sensor

#Thermistor's characteristics
SERIES_RESISTOR = 10000              #Resistance in Ohms
BETA = 3950                          #B-value for thermistor
ADC_MAX = 65535                      #16-bit ADC Max value

#LCD's characteristics
LCD_ROWS = 2
LCD_COLUMNS = 16
UPDATE_INTERVAL = 1               #Time between updates given in seconds

#Setting up I2C for the LCD
i2c = I2C(0, sda=Pin(0), scl=Pin(1), freq=100000)
lcd = I2cLcd(i2c, I2C_ADDR, LCD_ROWS, LCD_COLUMNS)

#Defining the PLC output channels as input pins
plc_inputs = {
    "FILL": Pin(18, Pin.IN, Pin.PULL_DOWN),
    "WASH": Pin(19, Pin.IN, Pin.PULL_DOWN),
    "DRAIN": Pin(20, Pin.IN, Pin.PULL_DOWN),
    "SPIN": Pin(21, Pin.IN, Pin.PULL_DOWN)
}

#Temperature reading function
def read_temperature():
    adc = ADC(Pin(THERMISTOR_PIN))
    analog_value = adc.read_u16()  # Reads the ADC value between 0-65535
    
    #Calculate resistance using voltage divider formula
    Resistance = SERIES_RESISTOR / (ADC_MAX / analog_value - 1)
    
    #Calculate temperature in Celsius using the Beta formula
    Celsius = 1 / (log(Resistance / SERIES_RESISTOR) / BETA + 1 / 298.15) - 273.15

    #Checking if the teperature is within 0-60 celsisus
    if Celsius < 0:
        return "Temp: Too Low"
    elif Celsius > 60:
        return "Temp: Too High"
    
    return "Temp: {:.1f}C".format(Celsius)

#Function to update the LCD display
def update_display(status, temperature_msg):
    lcd.clear()              #Clears LCD with each update
    
    #Displays status and temperature
    lcd.putstr("Status: {}\n".format(status))
    lcd.putstr(temperature_msg)

#Function to determine the current washer status
def get_washer_status():
    for mode, pin in plc_inputs.items():
        if pin.value() == 1:
            return mode  #Returns to the active mode
    return "IDLE"  #Default status if none of the modes are active

#Main loop
previous_status = None
previous_temperature_msg = None

while True:
    status = get_washer_status()
    
    try:
        temperature_msg = read_temperature()
    except Exception as e:
        temperature_msg = "Temp: Error"  #Displays to indicate an issue

    #Updates the display only if the status or temperature message has changed
    if status != previous_status or temperature_msg != previous_temperature_msg:
        update_display(status, temperature_msg)
        previous_status = status
        previous_temperature_msg = temperature_msg

    time.sleep(UPDATE_INTERVAL)  #Updates in specified time