Anyone know how I can build a keypad for my arduino project? lets say 8 buttons... maybe use i2c interfacing?
If you don't want to use any external ICs, the best way to have more than 5 buttons would be to implement a matrix keypad. For this see:
Arduino Playground - KeypadTutorial
If you are fine in using an external IC, see:
Arduino Playground - I2CPortExpanderAndKeypads
For 5 buttons or less, the answer provided by kidiccurus would be the better option
