illusion

I/O Port Operations / By /

Due to the persistence of vision our eye can’t distinguish what happen in TV. A full movie consists of numbers of pictures that move so fast that we can’t separate them. We will now make a program in which two 7 segment display on-off too fast that we will see a running digit.

In the picture if µC pin is zero 7 segment display will active otherwise inactive.

Let run a simple program and see what happen in proteus.

#include<avr/io.h>
#include<util/delay.h>
int main(void)
{
	DDRD=0xff;					//7 segment display PORT
	DDRB=0x03;					//7 seg control pin PD[0,1]
while(1)
	{
		PORTB=(1<<0);			//7 segment corresponding to mcu pin--PINB0 active
		PORTD=0b01100000;   	//display 1
		_delay_ms(5);			//5ms delay
		PORTB=0x03;				//Dark condition
		_delay_ms(20);			//20ms delay
		PORTB=(1<<1);			//7 segment corresponding to mcu pin--PIND1 active
		PORTD=0b11011010;		//display 2
		_delay_ms(5);			//5ms delay
		PORTB=0x03;				//Dark condition
		_delay_ms(20);          //20ms delay
	}
return 0;
}

In this program first display 1 after that dark condition arise than display 2 in another 7 segment after that dark condition arise and the process repeat. The delays are so adjust so that our eye can’t distinguish and we see a running 7 segment. This trick is so simple and we use it in our next part that counting visitors.

download

Download the full program with proteus simulation