import machine
from machine import Pin, I2C
import ssd1306
import math

# ESP32 Pin assignment 
i2c = I2C(0, scl=Pin(22), sda=Pin(21))

oled_width = 128
oled_height = 64
oled = ssd1306.SSD1306_I2C(oled_width, oled_height, i2c)

class TemperatureSensor:
    """This class takes in an an adc_pin for ESP32,
        a reference voltage, and a resolution in bits.
        It returns the temperature in Celsius
        using NTC temperature sensor. 
        Commented out is the version for LM35 temperature sensor.
        """
    def __init__(self, adc_pin, v_ref, resolution):
        """This function initializes adc,
            reference voltage, and max level."""
        self.__v_ref=v_ref
        self.__adc=machine.ADC(machine.Pin(adc_pin))
        self.__adc.atten(machine.ADC.ATTN_11DB) # full range of levels?
        self.__adc.width(eval(f"machine.ADC.WIDTH_{resolution}BIT"))
        self.__max_level=2**resolution-1
    def read_temperature(self, oled, LM35ADC=False):
        """This function reads the temperature
            and returns it using 10mV per degree Celsius conversion
            or conversion factor for NTC using Steinhart constants."""
        A = 0.001129148
        B = 0.000234125
        C = 0.0000000876741
        while True:
            reading=self.__adc.read()
            voltage=(reading/self.__max_level)*self.__v_ref 
            R0=10000
            if LM35ADC:
                temperature=voltage/(10/1000) # for LM35
            else:
                rt = (voltage*R0)/(self.__v_ref - voltage)
                temperature = 1/(A + (B * math.log(rt)) + C*math.pow(math.log(rt), 3))-273.15
            # clear the screen
            oled.fill(0)
            oled.text(str(f"T:{temperature:.1f}-deg C."), 10, 10)   
            print(f"{reading} {temperature}")   
            oled.show()

sensor=TemperatureSensor(adc_pin=2, v_ref=5, resolution=10)
sensor.read_temperature(oled)