Question

The microcontroller is AVR and the processor in it is ATMEGA8. I wrote a piece that followed the black color. It is like :

#include<avr/io.h>
#include<util/delay.h>
int main()
{
int rs,ls; // denotes the right sensor and left sensor respectively 
DDRC=0x00; // DENOTES THAT WE TAKE INPUT FROM THE SENSER
DDRB=0xFF; // DENOTES THAT PORT IS MEANT FOR THE OUTPUT FROM THE MOTOR
while(1) {
 ls=PINC&0b0000001; // last bit on
 rs=PINC&0b0001000; // 1st bit on

 if((ls==0b0000001)&(rs==0b0001000))
  PORTB=0b00010010; // forward
 if((ls==0b0000001)&(rs==0b0000000))
  PORTB=0b00000010; // right
 if( (ls==0b0000000) & (rs==0b0001000))
  PORTB=0b00010000; // left
 if((ls==0b0000000)&(rs==0b0000000) )
  PORTB=0b00010010; // stop
}
}

I am trying to write for the edge avoider. It has the same sensors that detect the black color. But now those sensers have to avoid a pit while moving on the table. I am unable to decide as to how i can do this.

NOTE : Sensor is able to detect the pit if there is nothing beneath it. But how do I am having problem writing code.

Answer 1

There can be many solutions for Edge Avoider. One implementation I have seen is –

Explanation –

• If none (left & right) is black (black = edge, white = table surface), you can keep moving forward.
• If any/both are black, you need to back off a little (CAUTION : This is tricky, in backing also, you may end up falling), and then change direction.

You need to experiment with delays, to get appropriate working.

These are the values needed below (I had omitted them before, because they are dependent on configuration)-

int move_backward = 0b00000110;
int right_turn = 0b00001010;
int move_forward = 0b00001001;
int left_turn = 0b00000101;

int left_sensor_on = 0b0010000;
int right_sensor_on = 0b0100000;
int left_sensor_off = 0b0000000;
int right_sensor_off = 0b0000000;

The below code should go inside while (1)

left_sensor = (PINC & 0b0000001); // This depends upon your configuration
right_sensor = (PINC & 0b0001000); // So I have used, the one from your code

if ((left_sensor==left_sensor_off) & (right_sensor==right_sensor_off))
{
    PORTB = move_backward;       //move backward
    _delay_ms(50);
    PORTB=right_turn;           //take a right turn
    _delay_ms(30);
    left_sensor = 0;
    right_sensor = 0;
}
if ((left_sensor==left_sensor_on) & (right_sensor==right_sensor_on))
{
    PORTB = move_forward;        //move forward
    left_sensor = 0;
    right_sensor = 0;
} 
if ((left_sensor==left_sensor_off) & (right_sensor==right_sensor_on))
{
    PORTB = move_backward;
    _delay_ms(50);
    PORTB = right_turn;
    _delay_ms(30);
    left_sensor = 0;
    right_sensor = 0;
}

if ((left_sensor==left_sensor_on) & (right_sensor==right_sensor_off))
{
    PORTB = move_backward;
    _delay_ms(50);
    PORTB = left_turn;
    _delay_ms(30);
    left_sensor = 0;
    right_sensor = 0;
}