Arduino Temp Monitor

/*

Code extracted from the Arduino Forum and mixed
with Temperature wby colors on arduinoarts.com

4 Digit 7 Segment display from Sparkfun
http://www.sparkfun.com/commerce/product_info.php?products_id=9480
 1: Digit 1    16: B
 2: Digit 2    15: G
 3: D      14: A
 4: Colon Anode    13: C
 5: E      12: Colon Cathode
 6: Digit 3    11: F
 7: Decimal Point  10: Apostrophe Anode
 8: Digit 4    9:  Apostrophe Cathode

 *************
 Display's Cathode goes to ground via resistor
 Display's Anode goes to digital out
 Digit pins go to digital out via resistor
 Segment pins (A-G) go to digital out or shift register out (0 is on)

Modified by @mrlndr for arduinoarts.com

*/

int clockPin = 12;  //Pin connected to SH_CP
int dataPin = 11;  //Pin connected to DS

int digit1Pin = 5;
int digit2Pin = 2;
int digit3Pin = 3;
int digit4Pin = 4;

byte data;
byte dataArray[13];

int tempPin = 0;     // the thermistor and 4,7k resistor

int temp=0;
int tempread;

const int MINUS_IDX = 10;
const int CELCIUS_IDX = 11;
const int FARENHEIT_IDX = 12;

void setup(){
  pinMode(digit1Pin, OUTPUT);
  pinMode(digit2Pin, OUTPUT);
  pinMode(digit3Pin, OUTPUT);
  pinMode(digit4Pin, OUTPUT);

  pinMode(latchPin, OUTPUT);

  Serial.begin(9600);

  dataArray[0] = B11000000;
  dataArray[1] = B11111001;
  dataArray[2] = B10100100;
  dataArray[3] = B10110000;
  dataArray[4] = B10011001;
  dataArray[5] = B10010010;
  dataArray[6] = B10000010;
  dataArray[7] = B11111000;
  dataArray[8] = B10000000;
  dataArray[9] = B10010000;

  //temperature specific characters
  dataArray[MINUS_IDX] = B10111111;  // minus sign
  dataArray[CELCIUS_IDX] = B11000110;  // C
  dataArray[FARENHEIT_IDX] = B10001110;  // F

}

void loop(){
  tempread = analogRead(tempPin);
  temp=tempread/19;
  // Serial.print("Temp = ");
  //Serial.println(temp); // reading the values
  setTemp(temp, 'C');
}

void setTemp(int temp, char scale){
  //temp must be between -99 and 999 in either scale to fit the display
  //put in a check here later
  boolean negative = false;
  if (temp < 0)
    negative = true;
  temp = abs(temp);

  if (scale == 'F'){
    setDigit(digit4Pin, FARENHEIT_IDX);
  } else if (scale == 'C'){
    setDigit(digit4Pin, CELCIUS_IDX);
  }

  setDigit(digit3Pin, temp % 10);
  temp /= 10;
  if (temp >= 1){
    setDigit(digit2Pin, temp % 10);
    temp /= 10;
    if (temp >= 1){
    setDigit(digit1Pin, temp % 10);
    }
  }
  if (negative){
    setDigit(digit1Pin, MINUS_IDX);
  }
}

void setDigit(int digitPin, int value){

    digitalWrite(latchPin, 0);
    shiftOut(dataPin, clockPin, dataArray[value]);
    digitalWrite(latchPin, 1);

    digitalWrite(digitPin, HIGH);
    delay(1);
    digitalWrite(digitPin, LOW);
}

void shiftOut(int myDataPin, int myClockPin, byte myDataOut) {
  // This shifts 8 bits out MSB first,
  //on the rising edge of the clock,
  //clock idles low

  //internal function setup
  int i=0;
  int pinState;
  pinMode(myClockPin, OUTPUT);
  pinMode(myDataPin, OUTPUT);

  //clear everything out just in case to
  //prepare shift register for bit shifting
  digitalWrite(myDataPin, 0);
  digitalWrite(myClockPin, 0);

  for (i=7; i>=0; i--)  {
    digitalWrite(myClockPin, 0);

    //if the value passed to myDataOut and a bitmask result
    // true then... so if we are at i=6 and our value is
    // %11010100 it would the code compares it to %01000000
    // and proceeds to set pinState to 1.
    if ( myDataOut & (1<<i) ) {
    pinState= 1;
    }
    else {
    pinState= 0;
    }

    //Sets the pin to HIGH or LOW depending on pinState
    digitalWrite(myDataPin, pinState);
    //register shifts bits on upstroke of clock pin
    digitalWrite(myClockPin, 1);
    //zero the data pin after shift to prevent bleed through
    digitalWrite(myDataPin, 0);
  }

  //stop shifting
  digitalWrite(myClockPin, 0);
}