Communication with Shields and Sensors

Hello,

What is the preferred method to send and receive information from shields. I release they can be stacked so it must be something specific.

Also, how many devices can you use with I2C. The reason I ask is that I have found a few sites that talk about different microcontrollers. In each of them they talk about arduinos only having 1 I2C and X number of SPI. Is that the number of I2C busses or what does that even mean? Isn't I2C just a protocol that you could use any of the pins to implement?

Thank you, Ben

I release they can be stacked so it must be something specific.

A safe assumption is that only one shield can be put on an arduino and the shield work. Putting on a second shield may make both not work.