MCP23017 to read hall sensors

But first you have to know how the forum works.

Installation and Troubleshooting is for Problems with the Arduino IDE itself NOT your project. It says so in the description of the section. Therefore I have moved your post here.

You might want to look at this [How to get the best from this from this Forum (How to get the best out of this forum) before you proceed any further.

Try reading this:-

It is the same chip inside, and the library they supply does contain examples.

It is worth knowing that I2C communications will be at the same speed no matter processor you use.