[En-Nut-Discussion] Port Usage

[Ole Reinhardt]

Hello Pete,

> I'm trying to figure out how to use Port E... 
> 
> I tried configuring bits 0 and 1 as inputs with the pullups disabled.
>  Never got it to work. Finally changed my code to use Port D instead.
>  Works.

You can just use port E0 / E1 if you disabled the serial port. In case
of NutOS you may not register DEV_USART0 or DEV_DEBUG0. 

> I realize that some ports do "double-duty." Is there a way to disable
>  the alternate functions and configure Port E as a regular I/O port? I
>  read the ATMEL 128 manual and I can't figure this out.

The ATMega128 will startup with all alternate functions disabled. So
what you not have explicitly enabled, will just be used as I/O ports. In
boot up configuration every port will be configured as input, without
pullups.

Bye,

Ole Reinhardt

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