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  1. /*********************************************
  2. * vim:sw=8:ts=8:si:et
  3. * To use the above modeline in vim you must have "set modeline" in your .vimrc
  4. * Author: Guido Socher, Copyright: GPL V2
  5. * This program is to test basic functionallity by getting an LED to blink.
  6. * See http://linuxfocus.org/English/November2004/  for details.
  7. * Chip type           : ATMEGA88
  8. *********************************************/
  9. #include <avr/io.h>
  10. #include <inttypes.h>
  11. #include <util/delay.h>
  12.  
  13.  
  14. void delay_ms(unsigned int ms)
  15. /* delay for a minimum of <ms> */
  16. {
  17.         // we use a calibrated macro. This is more
  18.         // accurate and not so much compiler dependent
  19.         // as self made code.
  20.         while(ms){
  21.                 _delay_ms(0.96);
  22.                 ms--;
  23.         }
  24. }
  25.  
  26. int main(void)
  27. {
  28.         /* INITIALIZE */
  29.         // Be very careful with low frequencies (less than 1MHz). Modern and fast programmers
  30.         // can not supply such low programming clocks. It can lock you out!
  31.         //
  32.         // set the clock prescaler. First write CLKPCE to enable setting of clock the
  33.         // next four instructions.
  34.         CLKPR=(1<<CLKPCE);
  35.         CLKPR=0; // 8 MHZ
  36.         //CLKPR=(1<<CLKPS0); // 4MHz
  37.         //CLKPR=((1<<CLKPS0)|(1<<CLKPS1)); // 1MHz
  38.         //CLKPR=((1<<CLKPS0)|(1<<CLKPS2)); // 0.25MHz
  39.  
  40.         /* enable PB1 as output */
  41.         DDRB|= (1<<DDB1);
  42.  
  43.         while (1) {
  44.                     /* led on, pin=0 */
  45.                     PORTB &= ~(1<<PB1);
  46.                     delay_ms(500);
  47.                     /* set output to 5V, LED off */
  48.                     PORTB|= (1<<PB1);
  49.                     delay_ms(500);
  50.         }
  51.         return(0);
  52. }
  53.  
  54.  
  55.