Spidey Sensor - Touch and Temperature

// NeoPixel Ring simple sketch (c) 2013 Shae Erisson
// released under the GPLv3 license to match the rest of the AdaFruit NeoPixel library

#include <Adafruit_NeoPixel.h>
#include <avr/power.h>

// Which pin on the Arduino is connected to the NeoPixels?
// On a Trinket or Gemma we suggest changing this to 1
#define PIN            4

// How many NeoPixels are attached to the Arduino?
#define NUMPIXELS      2

// thermistor voltage divider input pin
#define TEMP_IN_PIN    A3

// exponent for sensitivity purposes
#define EXPONENT       2

// define the sensitivity of the temperature meastuement
// smaller numbers are more sensitive, change from 16 to 256 in binary progression
#define TEMP_SENSITIVITY    80

// define the offset of the Temperature
// typical values are around 512, give or take 200 or so but 512 is the central number
#define TEMP_OFFSET         700
// When we setup the NeoPixel library, we tell it how many pixels, and which pin to use to send signals.
// Note that for older NeoPixel strips you might need to change the third parameter--see the strandtest
// example for more information on possible values.
Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);



void setup()
{
  pinMode(TEMP_IN_PIN, INPUT);  // temperature input (reads thermistor voltage divider)

  pixels.begin(); // This initializes the NeoPixel library.
}



void loop()
{
  // read in the temperature
  int temperatureInput = analogRead(TEMP_IN_PIN);

  // maptemperature to a sigmoid function
  float tempColorCold = 64.0 / (1.0 + exp( (TEMP_OFFSET - temperatureInput) / TEMP_SENSITIVITY ) );
  float tempColorHot = 64.0 - tempColorCold;

  // For a set of NeoPixels the first NeoPixel is 0, second is 1, all the way up to the count of pixels minus one.
  // pixels.Color takes RGB values, from 0,0,0 up to 255,255,255
  pixels.setPixelColor(0, pixels.Color(0, 0, 0)); // Moderately bright green color.
  pixels.setPixelColor(1, pixels.Color(0, tempColorHot, tempColorCold)); // Moderately bright green color.
  pixels.show(); // This sends the updated pixel color to the hardware.
}