The previous blinky project is very similar to what is presented here, with one exception. The delay function has been replaced by internal timer. In our circuit a LED is connected to PB0 and it is made to blink for roughly every second by using timer COMPA. The code is on Github, click here.
List of elements:
- ATtiny13 – i.e. MBAVR-1 development board
- VCC – power supply 3.3V/5V
- Resistor – 220Ω, see LED Resistor Calculator
- LED
Circuit Diagram
Firmware
This code is written in C and can be compiled using the avr-gcc. More details on how compile this project is here.
#include <avr/io.h>
#include <avr/interrupt.h>
#define LED_PIN PB0
ISR(TIM0_COMPA_vect)
{
PORTB ^= _BV(LED_PIN); // toggle LED pin
}
int
main(void)
{
/* setup */
DDRB = 0b00000001; // set LED pin as OUTPUT
PORTB = 0b00000000; // set all pins to LOW
TCCR0A |= _BV(WGM01); // set timer counter mode to CTC
TCCR0B |= _BV(CS02)|_BV(CS00); // set prescaler to 1024 (CLK=1200000Hz/1024/256=4.57Hz, 0.22s)
OCR0A = 255; // set Timer's counter max value
TIMSK0 |= _BV(OCIE0A); // enable Timer CTC interrupt
sei(); // enable global interrupts
/* loop */
while (1);
}
