Teensy (ATmega32U4) on-chip temperature sensor

[Agnes825]

I'm trying to read temperature data in Celsius and Fahrenheit by using Teensy's 2.0 on chip temperature sensor. I know that since i'm trying to use the on chip temperature sensor, I have to work with ADMUX and MUX to get the voltage value then convert them to Celsius and Fahrenheit but i'm not sure what to do regarding the ADMUX and MUX.

int sensorPin = 0; //the analog pin is connected to
                   //the resolution is 10 mV / degree centigrade with a
                   //500 mV offset to allow for negative temperatures

/*
 * setup() - this function runs once when you turn your Arduino on
 * We initialize the serial connection with the computer
 */
void setup()
{
  Serial.begin(9600);  //Start the serial connection with the computer
                       //to view the result open the serial monitor 
}

void loop()                     // run over and over again
{
  // gets voltage reading from the temperature sensor at analog in 0
  int reading = analogRead(sensorPin); 

  // converts reading to voltage, for 3.3v arduino use 3.3
  float voltage = reading * 5.0;
  voltage /= 1024.0; 

  // Print sensor 1
  Serial.println("Temperature Sensor 1");

  // Print out the voltage
  Serial.print(voltage);
  Serial.println(" volts");

  // converts voltage reading to temperature in degree Celsius
  float temperatureC = (voltage - 0.5) * 100 ;  //converting from 10 mv per degree wit 500 mV offset
                                                //to degrees ((voltage - 500mV) times 100)

  // Prints out temperature with unit Celcius
  Serial.print(temperatureC);
  Serial.println(" degrees C");

  // converts Celcius to Fahrenheit
  float temperatureF = (temperatureC * 9.0 / 5.0) + 32.0;

  // Prints out temperature with unit Fahrenheit
  Serial.print(temperatureF);
  Serial.println(" degrees F");

  // Converts Celcius to Kelvin
  float temperatureK = temperatureC + 273;

  // Prints out temperature with unit Kelvin
  Serial.print(temperatureK);
  Serial.println(" degrees K");

  delay(1000);  //waiting a second
}

 

[manitou]

Here is a sketch that reads leonardo/teensy2 internal temp sensor

// internal temp adc 8 for littlebits/leonardo  teensy 2
// we do raw  ADMUX or patch wiring_analog.c
//  http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1252144888
// calibration http://nyfiken.org/filer/kalibrering.ods

void setup() {
  Serial.begin(9600);
  ADMUX = _BV(REFS1) | _BV(REFS0) | 7;   // Set internal V reference, temperature reading
  ADCSRB = 0x20;    // ref  24.6
  delay(100);
  chipTempRaw(); // discard first sample
}

void loop() {
  int raw = chipTempRaw();
  float temp = chipTemp(raw);
  float ftemp = 1.8f * temp + 32;
  Serial.print(temp);
  Serial.print("  ");
  Serial.print(ftemp);
  Serial.print("   ");
  Serial.println(raw, DEC);
  delay(1000);
}

float chipTemp(float raw) {
  const float chipTempOffset = -142.5;
  const float chipTempCoeff = .558;
  return((raw * chipTempCoeff) + chipTempOffset);
}

int chipTempRaw(void) {
  ADCSRA &= ~(_BV(ADATE) |_BV(ADIE)); // Clear auto trigger and interrupt enable
  ADCSRA |= _BV(ADEN) | _BV(ADSC);        // Enable AD and start conversion
  while((ADCSRA & _BV(ADSC)));             // Wait until conversion is finished
  return(ADCL | (ADCH << 8));
}

You will probably need to calibrate coefficients in chipTemp(). I usually put the board in freezer for 20 minutes, then record temperature and output from chipTemp as board warms and do a least-squares fit to get coefficients.

 

[Agnes825]

Here is a sketch that reads leonardo/teensy2 internal temp sensor

// internal temp adc 8 for littlebits/leonardo  teensy 2
// we do raw  ADMUX or patch wiring_analog.c
//  http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1252144888
// calibration http://nyfiken.org/filer/kalibrering.ods

void setup() {
  Serial.begin(9600);
  ADMUX = _BV(REFS1) | _BV(REFS0) | 7;   // Set internal V reference, temperature reading
  ADCSRB = 0x20;    // ref  24.6
  delay(100);
  chipTempRaw(); // discard first sample
}

void loop() {
  int raw = chipTempRaw();
  float temp = chipTemp(raw);
  float ftemp = 1.8f * temp + 32;
  Serial.print(temp);
  Serial.print("  ");
  Serial.print(ftemp);
  Serial.print("   ");
  Serial.println(raw, DEC);
  delay(1000);
}

float chipTemp(float raw) {
  const float chipTempOffset = -142.5;
  const float chipTempCoeff = .558;
  return((raw * chipTempCoeff) + chipTempOffset);
}

int chipTempRaw(void) {
  ADCSRA &= ~(_BV(ADATE) |_BV(ADIE)); // Clear auto trigger and interrupt enable
  ADCSRA |= _BV(ADEN) | _BV(ADSC);        // Enable AD and start conversion
  while((ADCSRA & _BV(ADSC)));             // Wait until conversion is [URL="https://mobdro.ooo"][COLOR="#000000"]mobdro[/COLOR][/URL] finished 
  return(ADCL | (ADCH << 8));
}

You will probably need to calibrate coefficients in chipTemp(). I usually put the board in freezer for 20 minutes, then record temperature and output from chipTemp as board warms and do a least-squares fit to get coefficients.

Thanks help for me..