Question

Write the C code required to configure pin 0 on port B to be an input with the pullup resistor enabled.

Answer 1

To make port as a input with pullups enabled and read data from port 0

DDRA = 0x00;

PORTA = 0xFF;

To make port B as a tri stated input

DDRB = 0x00;

PORTB = 0x00;

To make lower nibble of port 0 as a output, higher nibble as a input with pullups enabled.

DDRA = 0x0F;

PORTA = 0xF0;

Blink LED on PB0 at a rate of 1Hz.

#include <mega16.h>
#include <delay.h>

void main()
{
    DDRB = 0xFF;         //PB as output
    PORTB= 0x00;         //keep all LEDs off

    while(1)
    {
        PORTB &= 0b11111110;       //turn LED off
        delay_ms(500);   //wait for half second
        PORTB |= 0b00000001;       //turn LED on 
        delay_ms(500);   //wait for half second
    };        
}

Blink LEDs on Port B with different patterns according to given input.

– Kit : use SW0, SW1
– No Kit : Connect a 2 micro-switches between pin PC0,PC2 and ground. So that when you press the switch pin is pulled low.

#include <mega16.h>
#include <delay.h>

//declare global arrays for two patterns
unsigned char p1[4] = { 0b10000001,
                        0b01000010,    
                        0b00100100,
                        0b00011000 };

unsigned char p2[4] = { 0b11111111,
                        0b01111110,    
                        0b00111100,
                        0b00011000 };
void main()
{
unsigned char i;                //loop counter

    DDRB = 0xFF;                //PB as output
    PORTB= 0x00;                //keep all LEDs off

    DDRC = 0x00;                //PC as input
    PORTC |= 0b00000011;        //enable pull ups for
                                //only first two pins

    while(1)
    {
        //# if SW0 is pressed show pattern 1
        if((PINC & 0b00000001)==0)                                           
        {
            for(i=0;i<3;i++)
            {
                PORTB=p1[i];    //output data
                delay_ms(300);  //wait for some time
            }
            PORTB=0;            //turn off all LEDs
        }

        //# if SW1 is pressed show pattern 2
        if((PINC & 0b00000010)==0)           
        {
            for(i=0;i<3;i++)
            {
                PORTB=p2[i];    //output data
                delay_ms(300);  //wait for some time
            }
            PORTB=0;            //turn off all LEDs
        }

    };