Hi Karan,

The Silabs C8051F120 uses a maximum supply voltage of 3.6V so the output normally only goes to 3.6V. The I/O pins will tolerate +5V however so you can use external resistors tied to +5V to make the outputs and inputs swing all the way to +5V.

The Silabs C8051F120 output pins can be programmed to be "open drain" or "push-pull" You need to program the outputs pins as "open drain" to allow the outputs to go to +5V however. If you program the output pins to be "push-pull" then the outputs will not go above 3.6V even with pull-up resistors. I would suggest 10Kohm pull-up resistors.

You have chosen a very powerful development system to start with. I hope you have already tried some simpler projects such as blinking a LED to get a bit familiar with the Silabs development system.

Cheers,

Bert