Digital I/O pin interaction with I2C Vin pin

[RiggerLee]

I'm having a problem with my digital I/O pins when I try to use a sensor break out board. When I plug in the Vin pin for the I2C all of my digital input pins, buttons, go to High.

I am very much a noob so please bear with me and speak slowly with small words.

History:

I'm using a Leonardo.

I went through the tutorials for digital read and got the buttons working on the digital pins 2 and 3.
The pins are set to input.
They are hooked to the ground through a resistor as shown in the youtube for idiots tutorial.
pressing the button connects them to 5v as in the tutorial.
They worked fine.

I got a sensor board from Adafruit. Adafruit's 10DOF breakout.
I went though their documentation and examples and got the BMP180 sensor working.
Every thing was reading fine.

As I began writing the code I found that when I had them both hooked up, buttons and sensor board that all of my digital input pins were reading High.

I checked this with just the bare example code for digital serial read, buttons, and found the same thing.

I tried using different ground pins, like the one next to the I2C pins for the I2C ground.

It's the Vin pin on the I2C board. When I have it hooked up both of my digital input pins 2 and 3 go to high.

The board says that it prefers 5v but can use 3.3v. I've tried the Vin pin in both the 5v and 3.3v. Same outcome. Both digital pins read high as if the button were being pushed.

I tried it with another Leonardo and got the same result.

I'm running out of ideas. I've stripped every thing else out of my code. I've tried it with off the shelf example code that does not examine the I2C at all. So I don't think it's a code thing. It seems to be a hardware issue. How does this work? How can I isolate the digital input out put pins from the I2C? How can I use them both?

I really don't know what I'm doing here. I seem to be missing some thing really fundamental but I can't find a reference to it and I'm not sure where to look for the answer.

To be clear, I'm a parachute rigger. Read that, glorified seamstress. I sew on things. I know nothing about digital electronics. Please help.

Lee

[adafruit_support_bill]

Pins 2 and 3 are also the i2c pins on the Leonardo. If you are using i2c, you will need to choose different pins for your buttons.

https://www.arduino.cc/en/Main/ArduinoBoardLeonardo