/* Analog LED Thermometer, by Karl Laun, March 2012

Circuit Description

 *******74HC595 wiring (1/2)*********
 
  595(1) drives LEDs 1-8 (lower bank)
  595(2) drives LEDs 9-16 (upper bank)
 
 Connect pins 10 (MR-reset) to +5v
 Connect pins 13 (OE-output enable) to GND
 Connect pins 8 (GND) to GND
 Connect pins 16 (Vcc) to +5v
 Connect pin 9(1) to pin 14(2) (serial out to data)
 Conect data(14), latch(12) and clock(11) pins to digital outputs (see define pins)
 
 ********* TMP36 wiring (facing flat side) ***********
 Connect pin 1 to +5v
 Connect pin 2 to analog input (see define pins)
 Connect pin 3 to GND

 */

// declare variables --------------------------------------
int LEDs[10] = {0, 1, 3, 7, 15, 31, 63, 127, 255, 128};  // set number of LEDs to light up
int tempRange[2] = {20, 95};  // set desired upper and lower Farenheit temps
int cutoff[15];  // array to store the intermediate steps between LED activations
int upperBank = 0;
int lowerBank = 0;
int samplePeriod = 1000; // set period for polling of temp sensor
int testDelay = 50;

// define pins --------------------------------------------
int dataPin  = 8;   // connect to pin 14(Ds)
int latchPin = 9;   // connect to pin 12(STcp) connect to both 595 chips
int clockPin = 10;  // connect to pin 11(SHcp) connect to both 595 chips
int tempPin = A3;   // connect to center pin on TMP36


void setup()
{
  Serial.begin(9600);

// define inputs/outputs
  pinMode(dataPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(tempPin, INPUT);

// run a sequential LED test
  for (int n=1; n < 9; n++) // lower bank
  {
    lowerBank = LEDs[n];
    sendTemp();
    delay(testDelay);
  }
  for (int j=1; j < 9; j++)  // lower + upper bank
  {
    lowerBank = LEDs[8];
    upperBank = LEDs[j];
    sendTemp();
    delay(testDelay);
  }
  delay(1000);  // keep all LEDs lit for a bit, then turn them all off
  upperBank = LEDs[0];
  lowerBank = LEDs[0];
  sendTemp();
  delay(samplePeriod);
  
// define the temperature cutoff increment points for the LEDs
  float incr =(((tempRange[1] - tempRange[0]) /15.0)); // 15 steps between 16 LEDs
  cutoff[0] = tempRange[0] + (incr /2.0);
  for (int i=1; i < 15; i++)
  {
   cutoff[i] = cutoff[0] + (i * incr);  
  }
}

void loop()
{
  int reading = analogRead(tempPin);        // read temperature probe voltage
  float probeVolts = reading * 5.0;         // adjust it to 5v / 1024 to get millivolts
  probeVolts  /= 1024.0;
  float tempC = (probeVolts - 0.5) * 100 ;  // convert voltage to degrees (subtract 500 mv offset)
  float tempF = (tempC * 9.0 / 5.0) + 32.0; // convert C to F
  
  Serial.print("Temp = ");  // send temperature to serial
  Serial.println(tempF);

// assign byte values to be sent to LEDs
  
  if(tempF > tempRange[1]) //  Warn if out of range (HOT)
    {
      upperBank = LEDs[9];
      lowerBank = LEDs[0];
      sendTemp();
      delay(testDelay);
      upperBank = LEDs[0];  
    }
  else if(tempF < tempRange[0])  // Warn if out of range (COLD)
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[1];
      sendTemp();
      delay(testDelay);
      lowerBank = LEDs[0];
    }
  else if(tempF >= tempRange[0] && tempF < cutoff[0]) //  Set 1-16 LEDs to light up depending on temp
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[1];
    } 
  else if(tempF >= cutoff[0] && tempF < cutoff[1])  
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[2];
    }  
  else if(tempF >= cutoff[1] && tempF < cutoff[2])
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[3];
    }
  else if(tempF >= cutoff[2] && tempF < cutoff[3])
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[4];
    }
  else if(tempF >= cutoff[3] && tempF < cutoff[4])
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[5];
    }
  else if(tempF >= cutoff[4] && tempF < cutoff[5])
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[6];
    }
  else if(tempF >= cutoff[5] && tempF < cutoff[6])
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[7];
    }    
  else if(tempF >= cutoff[6] && tempF < cutoff[7])
    {
      upperBank = LEDs[0];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[7] && tempF < cutoff[8])
    {
      upperBank = LEDs[1];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[8] && tempF < cutoff[9])
    {
      upperBank = LEDs[2];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[9] && tempF < cutoff[10])
    {
      upperBank = LEDs[3];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[10] && tempF < cutoff[11])
    {
      upperBank = LEDs[4];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[11] && tempF < cutoff[12])
    {
      upperBank = LEDs[5];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[12] && tempF < cutoff[13])
    {
      upperBank = LEDs[6];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[13] && tempF < cutoff[14])
    {
      upperBank = LEDs[7];
      lowerBank = LEDs[8];
    }
  else if(tempF >= cutoff[14] && tempF <= tempRange[1])
    {
      upperBank = LEDs[8];
      lowerBank = LEDs[8];
    }

  sendTemp();           // send to LEDs function
  delay(samplePeriod);  // wait awhile for next update
}


// Send bytes to 74HC595 chips to light LEDs
void sendTemp()
{
  digitalWrite(latchPin, LOW);                      // latch LOW to send data
  shiftOut(dataPin, clockPin, MSBFIRST, upperBank); // send byte for LEDs 1-8
  shiftOut(dataPin, clockPin, MSBFIRST, lowerBank); // send byte for LEDs 9-16(shift upper)
  digitalWrite(latchPin, HIGH);                     // latch HIGH to stop data transfer
}