Hi I am new to electronics and uC, here is a tutorial I came across and play around with the code, and I find out:

• I don't have to set a port as input, and it can still act as an input port;

• And there is no different if I turn on internal pull-up resistor or not, my program still function as normal

My program is simply turn a LED on when button is pressed, and turn a LED off again when the button is pressed again, the program is running in a stk500.

Can someone explains it please?

#define INPUT_PORT PORTD
#define INPUT_DDR DDRD
#define INPUT_PIN PIND
#define INPUT_BIT PD0

INPUT_DDR &= ~(_BV(INPUT_BIT)); //set as input
INPUT_PORT |= _BV(INPUT_BIT); // turn on internal pull-up resistor for the switch

full code is attached

 

never mind, I found out the answer already

 

Even-though you found the answer you should not have mentioned it. It had made your thread DEAD.

 

Lol thanks for your advice, I thought if I got the answer, then should not waste other peoples time

 

i disagree with @android.. you should post if you solve it.. but you should say what was wrong with it.

 

i disagree with @android.. you should post if you solve it.. but you should say what was wrong with it.

As request:

• The pin I was using is set as input by default(AVR at90s8515)
• There is an external pull up resistor connected to all led at my development board(stk500)

 

never mind, I found out the answer already

Remember that this forum is not just above solving your problem.
You can contribute valuable community service by explaining how you solved your problem.

 

i disagree with @android.. you should post if you solve it.. but you should say what was wrong with it.

Yeah. Of course. He should've explained the cause. Firstly, I entered in this thread to answer it & then I saw him saying 'I found it'. So instead of answering the question I said that.