Blinking LED using Atmega32 Microcontroller and Atmel Studio

Similar to printing ‘Hello World’ in C or C++, the very first step towards programming a microcontroller is Blinking a LED with a delay. Atmega32 is a very popular high performance 8 bit AVR Microcontroller. For this example project we need to use two registers DDR and PORT. DDR stands for Data Direction Register, it determines the direction (Input/Output) of each pins on the microcontroller. HIGH at DDR register makes corresponding pin Output while LOW at DDR register makes corresponding pin Input. PORT register is the output register which determines the status of each pin of a particular port. HIGH at PORT register makes corresponding pin Logic HIGH (5V) while LOW at PORT register makes corresponding pin Logic LOW (0V).

Circuit Diagram

LEDs are connected to PORTC and current limiting resistors are used to limit current through them. 16 MHz crystal is used to provide clock for the Atmega32 microcontroller and 22pF capacitors are used to stabilize the operation of crystal. The 10µF capacitor and 10KΩ resistor is used to provide Power On Reset (POR) to the device. When the power is switched ON, voltage across capacitor will be zero so the device resets (since reset is active low), then the capacitor charges to VCC and the reset will be disabled. 30th pin (AVCC) of Atmega32 should be connected to VCC if you are using PORTA, since it is the supply voltage pin for PORT A.

#ifndef F_CPU 
#define F_CPU 16000000UL // 16 MHz clock speed
#include < avr/io.h/ > 
#include < util/delay.h>

int main(void)
  DDRC = 0xFF; //Nakes PORTC as Output
  while(1) //infinite loop
    PORTC = 0xFF; //Turns ON All LEDs
    _delay_ms(1000); //1 second delay
    PORTC= 0x00; //Turns OFF All LEDs
    _delay_ms(1000); //1 second delay
  • DDRC = 0xFF makes all pins on PORTC as output pins
  • PORTC = 0xFF makes all pins on PORTC Logic High (5V)
  • PORTC = 0x00 makes all pins on PORTC Logic Low (0V)
  • _delay_ms(1000) provides 1000 milliseconds delay.
  • while(1) makes an infinite loop.

You have seen that PORT registers are used to write data to ports. Similarly to read data from ports PIN registers are used. It stand for Port Input Register. eg : PIND, PINB You may like to set or reset individual pins of PORT or DDR registers or to know the status of a specific bit of PIN register. There registers are not bit addressable, so we can’t do it directly but we can do it through program.