1.1V reference voltage attiny85

I am using a TMP36 sensor and want to measure temperature with the 1.1V reference scale but instead of 19C I am getting -34C. This is the result of using the calculation for 1.1V but actually the analog read referenced 5V

I’m using the Google Code Tiny core with my ATTINY85. I checked wiring.h and I have the correct syntax.
Why isn’t the reference voltage 1.1V?

#include <RH_ASK.h>
//#include <SPI.h> // Not actually used but needed to compile
// 0 1 0 Internal 1.1V Voltage Reference.
#define INTERNAL (2)

int TEMPERATURE_PIN = A1; //the temp sensor pin
int TRANSISTOR_PIN = 1; //pin that turn ON and OFF the transistor

int SensorData;
int Temp;
char SensorCharMsg[4]; 

RH_ASK driver(2000, 9, 3);
// 200bps, TX on D3 (pin 2), RX on D4 (pin 3) then: Connect D3 (pin 2) as output to transmitter Connect D4 (pin 3) as input from receiver

void setup()

void loop()
  int SensorData = analogRead(TEMPERATURE_PIN); //read the TMP36
  float voltage = (SensorData / 1024.0) * 1.1;
  int Temp = (voltage - 0.5) * 100.0;
    // Convert integer data to Char array directly 
    //turn ON the transistor to power transmitter then send the message then turn OFF the transistor*/
    digitalWrite(TRANSISTOR_PIN, HIGH);//transistor ON

    driver.send((uint8_t *)SensorCharMsg, strlen(SensorCharMsg));

    digitalWrite(TRANSISTOR_PIN, LOW);//turn OFF transistor to save battery


I don't see where you are changing the reference voltage.


You have to call that function.

I thought the define statements at the top of the code were sufficient to change the reference voltage.

I previously saw the link you posted but didn't understand it was a function to be entered in the code.

Thanks for the help!

The Tiny Core already provides those #defines... https://code.google.com/p/arduino-tiny/source/browse/cores/tiny/wiring.h#114

Including them in your sketch is a mistake.