Saturday, March 21, 2009

Hello AVR!

Finally, my first AVR micro-controller based project is ON! I always had a great passion for embedded electronics, but never had a chance and guidance to improve. This is a first step towards that -- thanks to the Internet for a handful of articles.

After a week's struggle to setup the whole environment, I managed to successfully flash my first program into my ATMega8 micro-controller and use it to drive 2 LEDs. The power of the ATMega8 is just amazing; with very little power consumption, the features it provides for embedded applications is just too good (In a 28pin PDIP packaging, it has around 23 I/O pins, 6 channel ADC, Pulse Width Modulation, Programmable USART, ISP, 3 Timers and clocking at 8-16MHz).

Why the struggle:

This shouldn't have been a struggle, if I wasn't unlucky to get a faulty ATMega8. This is my first AVR project and I had bought tonnes of electronic goods starting from multimeter, soldering iron to AVR ISP programmer, ATMega8, crystals, resistors, capacitors, inductors, LEDs....(I've actually bought more stuff which I'm yet to use). After setting up the circuit as required, connecting the micro controller (uC) to the ISP programmer and the programmer to the computer, I was not able to flash my controller at all and that was the problem :( I struggled struggled and struggled to debug every portion of this chain; tried a different ISP programmer (built my own serial ISP programmer) but no use; after achieving no success, the final and the only option was to suspect my ATMega8 uC -- the hero of this project. Anyone would think why it took me so long to suspect this; True. But I did suspect this earlier, however I wished this wasn't the issue because I didn't have a spare one with me and I cannot get this in the nearby electronics shops. Finally I had to personally go to SP road in Bangalore (Bangalore's version of the Chennai's ritchie street) and get a ATMega8. Sigh!!! All said and done, it is finally working :D

This is pretty much a 'Hello World' nothing else. The uC just drives the 2 LEDs I have connected over PORTC through the 330ohm current limiting resistors. To keep it a bit fancy, I made the 2 LEDs to represent the last 2 bits of a running integer counter. So basically the LEDs glow in the following pattern as the integer keeps incrementing -- 00, 01, 10, 11. A 500ms delay between the increments, to keep it visible to the eye.

The code would look something like this (I use the WinAVR cross compiler).

#include <avr/io.h>
#include <util/delay.h>

int main()
DDRC = 0xFF; // Enable output on PORT C
uint8_t c = 1;
while(1) {
PORTC = c++; // output the integer on PORT C, whose 0-1bits drive the LEDs
return 0;
Here is the Hello AVR! in action:

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