from machine import Pin

class MAX6675:
    def __init__(self, cs, sck, so):
        self.cs = cs
        self.sck = sck
        self.so = so
        cs.init(Pin.OUT) # Chip select pin, active low
        sck.init(Pin.OUT) # Clock, driven by host
        so.init(Pin.IN) # Data, driven by MAX6675

    def read(self):
        reading = 0
        self.cs.off() # Active low
        for i in range(16):
            self.sck.off()
            self.sck.on()
            reading = (reading << 1) + self.so.value()
        self.cs.on()
        
        if reading & 0x04:
            raise ValueError("Thermocouple disconnected")

        degC = (reading >> 3) * 0.25
        return(degC)