What can i change in this code to make it work?

Question

This C code, Atmel Studio, is supposed to check pins 2 and 3 on PORTD which is connected to a 4 direction tilt sensor (Up, down, left, right) then lights up 4 different LEDs for each direction. LEDs are connected on PORTB.

code:

#include <avr/io.h>

#include <util/delay.h>

#ifndef F_CPU
#define F_CPU   16000000UL
#endif




//// define input sensor on PORT D
//
//#define tilt_S1 (PIND&(1<<2))
//#define tilt_S2 (PIND&(1<<3))
//
////define output LEDs on PORT B
//
//#define LED_U (PINB&(1<<0))
//#define LED_D (PINB&(1<<1))
//#define LED_L (PINB&(1<<2))
//#define LED_R (PINB&(1<<3))





int main(void)
{
    DDRD =0x00; //port d as input
    DDRB =0xFF; //port b as out
    
    
    while (1)
    {
        //int pos = GetTiltPos();     //get current sensor position
        
        
        if ( ( (PIND & (1<<2))==0 ) && ((PIND & (1<<3))==0 ) )  //Up (North) [S1=0, S2=0]
        {
            PORTB |=  1<<PINB0;    //up   turn on TOP led only
            PORTB &= ~(1<<PINB1); //down
            PORTB &= ~(1<<PINB2); //left 
            PORTB &= ~(1<<PINB3);  //right
        }
        
        
        else if (((PIND & (1<<2))==1 ) && ((PIND & (1<<3))==0 ))   //Left (West)  [
        {
            PORTB &=  ~(1<<PINB0);    //up   
            PORTB &=  ~(1<<PINB1);    //down
            PORTB |=   1<<PINB2;       //left       turn on LEFT led only
            PORTB &=  ~(1<<PINB3);    //right
        }
        
        else if (((PIND & (1<<2))==0) && ((PIND & (1<<3))==1))    //Right (East)
        {
            PORTB &= (~(1<<PINB0));    //up   
            PORTB &= (~(1<<PINB1));    //down
            PORTB &= (~(1<<PINB2));    //left
            PORTB |=  (1<<PINB3);       //right    turn on RIGHT led only
        }
        else if ( ((PIND & (1<<2))==1 ) && ((PIND & (1<<3))==1 ) )     //Down (South)
        {
            PORTB &= ~(1<<PINB0);      //up   
            PORTB |=   1<<PINB1;         //down    turn on BOTTOM led only
            PORTB &= ~(1<<PINB2);      //left
            PORTB &= ~(1<<PINB3);      //right
        }
        
    }
}

//int GetTiltPos()   //function to determine position of sensor
//{
    //int S1 = 1<<PIND2;
    //int S2 = 1<<PIND3;
    //int R = ((S1<<1)| S2) ;
    //return R;
//
//}

i tried defining the LEDs and sensors first, but that didn't work so i tried reading from the pin directly But that wont work either and I don't understand why. This code results in the upper LED to be always ON. the sensor used is the 4 direction tilt sensor RPI-1031

Answer 1

The expression (PIND & (1<<2))==1 will never be true. The result of (PIND & (1<<2)) will either be 0 or 8 ( 1<<2 ). An easy way to avoid this issue is to always check for equal or not equal to zero, such as (PIND & (1<<2)) != 0 .

Answer 2

1. You read from PINB instead of PIND (example: (PINB & (1<<2)) ) - i should be (PIND & (1<<2))
2. You do not set the port D as input as |= does not not work the way you think

DDRD |=0x00; //port d as input

This line does nothing. If you want to zero the register you need to:

DDRD = 0;

or if you only need to zero some of the bits on the register (for example bit 1,3 & 5)

DDRD &= ~((1 << 1) || (1 << 3) | (1 << 5));