max6675_demux74138

This Arduino lib was made in order to use more than one MAX6675-based Thermocouple in combination with a 74138 Demultiplexer IC, allowing up to 8 thermocouples to be read with less than 8 selection pins.

Connections:

-All Thermocouple SCLK pins are connected to the same Arduino SPI clock pin;
-All Thermocouple SO pins are connected to the same Arduino SPI MISO pin;
-Each Thermocouple CS pin is connected to a different output of the 74138 Demux (¬O0 to ¬O7);
-Each Demux selector pin (A0, A1 and A2) is connected to a different digital pin on Arduino;
-Only one of the Demux enable pins (¬E1, ¬E2 or E3) is connected to a digital pin on Arduino; 
-The other enable pins are connected to Vcc or GND, corresponding to its active state (Active high = Vcc, Active low = GND).

Functions:

MAX6675demux(int8_t SCLK, int8_t* DEMUX_PINS, int8_t EN, int8_t MISO, uint8_t ACTIVE_EN=LOW)
    -Constructor function;
    -SCLK: SPI clock pin;
    -DEMUX_PINS: Demux selector pins. The "0" index of the array (first element) corresponds to A0 pin, "1" to A1, and "2" to A2;
    -EN: Demux enable pin;
    -MISO: SPI Slave Out pin;
    -ACTIVE_EN: State in which the EN pin is set to be active.
    
double readCelsius(int8_t index)
    -Returns the temperature in Celsius format;
    -index: Number of the demux output pin in which the wanted termocouple CS is connected.
    
double readFahrenheit(int8_t index)
    -Returns the temperature in Fahrenheit format;
    -index: Number of the demux output pin in which the wanted termocouple CS is connected.
    
double readFarenheit(int8_t index)
    -Same as readFahrenheit(int8_t index).