The document discusses interfacing LEDs with microcontrollers. It explains that LEDs are PN junction semiconductors that emit monochromatic light when forward-biased. It describes the data direction register (DDR) which determines whether pins on a given port are inputs or outputs. It also discusses the PORT register which sets the data values on pins. Finally, it provides a code example that blinks LEDs connected to port C using these registers and a delay function.

1. INTERFACING LEDS WITH
MICROCONTROLLER

2. A light-emitting diode (LED) is a PN junction
semiconductor which emits monochromatic(single) light.
When forward-biased (switched on), electron hole
recombination releases energy in the form of photons.
LIGHT EMITTING DIODES

3. Two configurations of LEDs……..
COMMON CATHODE COMMON ANODE

4. INTERFACING

5. DDR X
Data Direction Register
DDR X is used to determine the direction of data on each pin of a given port X
Logic 1 -> specify pin as output port
Logic 0 -> specify pin as input port
Ex- DDRC=0 b 1 1 1 1 1 0 0 0 ;
DDRC=0XF8;
PC0 , PC1 , PC2 -> INPUT PINS
PC3 , PC4 , PC5, PC6 , PC7 -> OUTPUT PINS

6. DDRB instruction gives the direction of data transfer as each port of atmega
16 is birectional..……
eg:DDRC=0b11110011;
0-- input
1-- output

7. INSTRUCTIONS USED
PORT X
PORT X is used to determine the data on each pin of a given port.
Ex- PORTC=0 b 1 1 1 1 1 0 0 0 ;

8. PORT instruction gives data to be sent on the port
eg- PORTC=0b01011011;
1
1
1
1
1

9. PORT instruction gives data to be sent on the port
eg- PORTC=0b01011011;

10. INSTRUCTIONS USED
_delay_ms();
It is used to provide a delay of specific time in milliseconds in the program.
Ex- _delay_ms(1000); ->provides delay of 1 second

11. PROGRAM-
#define F_CPU 16000000
#include <avr/io.h>
#include <util/delay.h>
int main(void)
{
DDRC=0 b 0 0 0 0 1 1 1 1;
//data direction register
for port C//
while( 1 )
{
//infinite loop//
PORTC=0 b 0 0 0 0 1 1 1 1 ; //Data on port C//
_delay_ms(1 0 0 0) ; //Delay of 1 sec//
PORTC=0 b 0 0 0 0 0 0 0 0 ;
_delay_ms(1 0 0 0) ;
}
}

12. OUTPUT
00:00 sec

13. OUTPUT
00:01 sec

14. OUTPUT
00:02 sec

15. OUTPUT
00:03 sec

16. Now try and generate the next
pattern on your
own……………………………………….

17. OUTPUT
00:01 sec

18. OUTPUT
00:02 sec

19. OUTPUT
00:03 sec

20. OUTPUT
00:04 sec