I recently bought a BMP180 Pressure Sensor, as well as an Arduino Due. Since the Due only operates at 3.3V, I wanted to make sure that I wouldn't fry it by hooking up a 5V SCL/SDA input. When I checked the voltage using a voltmeter, it seems that the SCL/SDA voltages are 4.93V for a 5V input but when I hook up VIN to the 3.3V pin on an Arduino Uno, the SCL/SDA voltages are 3.9V. Upon further investigation, the 3.3V pin seems to deliver 3.3V when not plugged into the BMP180, but when I connect the wires to the breakout board, my volt meter registers a voltage fluctuating between 3.45V and 3.65V.
Will it be okay to use the BMP180 on an Arduino Due, if the SCL/SDA voltages are at 3.9V and not 3.3?
Also, why would the input voltage increase when the board is connected? If I had to guess, I would think that there is some sort of back EMF from the voltage regulator or some other component on the breakout board. However, I find it strange that this only happens for a 3.3V input and not a 5V input.