/******************   Arduino Smile with 8x8 Matrix and temp  ******************/
#include <SPI.h>
#define CS 10

// MAX7219 Control registers
#define DECODE_MODE 9 
#define INTENSITY    0x0A
#define SCAN_LIMIT   0x0B 
#define SHUTDOWN     0x0C
#define DISPLAY_TEST 0x0F

byte sadFace   [8] = {0x00,0x66,0x66,0x00,0x3C,0x42,0x42,0x00};
byte happyFace [8] = {0x00,0x66,0x66,0x00,0x42,0x42,0x3C,0x00};

const float BETA = 3950; // should match the Beta Coefficient of the thermistor

void SendData(uint8_t address, uint8_t value) {  
    digitalWrite(CS, LOW);   
    SPI.transfer(address);      // Send address.
    SPI.transfer(value);        // Send the value.
    digitalWrite(CS, HIGH);     // Finish transfer.
}
void setup() {
    pinMode(CS, OUTPUT);  
    SPI.setBitOrder(MSBFIRST);              // Most significant bit first 
    SPI.begin();                            // Start SPI
    SendData(DISPLAY_TEST, 0x01);           // Run test - All LED segments lit.
    delay(1000);
    SendData(DISPLAY_TEST, 0x00);           // Finish test mode.
    SendData(DECODE_MODE, 0x00);            // Disable BCD mode. 
    SendData(INTENSITY, 0x0e);              // Use lowest intensity. 
    SendData(SCAN_LIMIT, 0x0f);             // Scan all digits.
    SendData(SHUTDOWN, 0x01);               // Turn on chip.
   
    Serial.begin(9600);
}
void loop()  {
    int analogValue = analogRead(A0);
    float celsius = 1 / (log(1 / (1023. / analogValue - 1)) / BETA + 1.0 / 298.15) - 273.15;
    
    Serial.print("Temperature: ");
    Serial.print(celsius);
    Serial.println(" ℃");

    if(celsius < 0.0)
    {
      for (int i=1;i<9;i++) SendData(i, sadFace[i-1]);
    }

    else if (celsius > 0.0 && celsius < 28.0)
    {
      for (int i=1;i<9;i++) SendData(i, happyFace[i-1]);
    }
    else
    {
      for (int i=1;i<9;i++) SendData(i, sadFace[i-1]);
    }

}