Just tried using my new AM2315 Humidity/Temperature sensor with a Teensy 2.0, and I am getting bad data.
This is an I2C device available from Adafruit Industries:

Link to the library:

The code is an example included with the AM2315 Library:
    #include <Wire.h>
    #include <Adafruit_AM2315.h>

      This is an example for the AM2315 Humidity + Temp sensor

      Designed specifically to work with the Adafruit BMP085 Breakout
      ----> https://www.adafruit.com/products/1293

      These displays use I2C to communicate, 2 pins are required to 
      Adafruit invests time and resources providing this open source code,
      please support Adafruit and open-source hardware by purchasing
      products from Adafruit!

      Written by Limor Fried/Ladyada for Adafruit Industries. 
      BSD license, all text above must be included in any redistribution

    // Connect RED of the AM2315 sensor to 5.0V
    // Connect BLACK to Ground
    // Connect WHITE to i2c clock - on '168/'328 Arduino Uno/Duemilanove/etc thats Analog 5
    // Connect YELLOW to i2c data - on '168/'328 Arduino Uno/Duemilanove/etc thats Analog 4

    Adafruit_AM2315 am2315;

    void setup() {
      Serial.println("AM2315 Test!");

      if (! am2315.begin()) {
         Serial.println("Sensor not found, check wiring & pullups!");
         while (1);

    void loop() {
      Serial.print("Hum: "); Serial.println(am2315.readHumidity());
      Serial.print("Temp: "); Serial.println(am2315.readTemperature());

Everything is wired the normal way, using a pair of 10K pullups to Vcc. I have made many successful gadgets using I2C in the past.

When I first start the system, the first 11 readings were normal at 24degC and 55.4%rh (close to a DHT-22 I also have running on a different system), but then the numbers went all weird- the Temperature value stuck at 3331.80 and the Humidity at 22.00 with minor variation (+/- 0.02% or so).

I tried disconnecting the USB, waiting 15 seconds, then plugged it in. Same thing.

The software is an un-modified (except for deleting an extraneous "}" at the end) example sketch that came with the Adafruit AM2315 library.

I ran exactly the same code for days with an Arduino Uno, with no difficulty.

I am currently using the Teensyduino 1.02 IDE.

Any clues will be most appreciated!

I posted this topic on the Adafruit board as well:
but have not received much helpful information yet.

Thank you!