trivial_demo.ino

#define PIN 0

#define K1  421.0

#define K2  751.0

uint32_t time_high, time_low, last_time, new_time;

float temperature;

void setup() {

  Serial.begin(12345);

  pinMode(PIN, INPUT);

  new_time = last_time = micros();

}

void loop() {

  while(digitalRead(PIN));

  new_time = micros();

  time_high = new_time - last_time;

  last_time = new_time;

  while(!digitalRead(PIN));

  new_time = micros();

  time_low = new_time - last_time;

  last_time = new_time;

  temperature = K1 - (K2 * time_high) / (float)time_low;

  Serial.print(time_low);  Serial.print("  ");

  Serial.print(time_high);  Serial.print("  ");

  Serial.println(temperature);

}