This post is based on classroom demonstration of Example 4-1 from book Make: AVR Programming by Elliot Williams. The demonstration has three variations in cylonEyes.c listing on pp. 60-61. The Proteus simulation model is shown below. Then comes program codes and a short movie clip.
// Example 4-1. cylonEyes.c modified listing 1
// ------- Preamble -------- //
#include <avr/io.h> /* Defines pins, ports, etc */
#include <util/delay.h> /* Functions to waste time */
#define DELAYTIME 1000 /* milliseconds */
#define LED_PORT PORTB
#define LED_PIN PINB
#define LED_DDR DDRB
int main(void) {
// -------- Inits --------- //
uint8_t i = 0;
LED_DDR = 0xff; /* Data Direction Register B: all set up for output */
// ------ Event loop ------ //
while (1) {
while (i < 7) {
LED_PORT = (1 << i); /* illuminate only i'th pin */
_delay_ms(DELAYTIME); /* wait */
i = i + 1; /* move to the next LED */
}
while (i > 0) {
LED_PORT = (1 << i); /* illuminate only i'th pin */
_delay_ms(DELAYTIME); /* wait */
i = i - 1; /* move to the previous LED */
}
} /* End event loop */
return (0);
}
// Example 4-1. cylonEyes.c modified listing 2
// ------- Preamble -------- //
#include <avr/io.h> /* Defines pins, ports, etc */
#include <util/delay.h> /* Functions to waste time */
#define DELAYTIME 1000 /* milliseconds */
#define LED_PORTB PORTB
#define LED_PINB PINB
#define LED_DDRB DDRB
#define LED_PORTD PORTD
#define LED_PIND PIND
#define LED_DDRD DDRD
int main(void) {
// -------- Inits --------- //
uint8_t i = 0;
uint8_t j = 0;
LED_DDRB = 0xff; /* Data Direction Register B: all set up for output */
LED_DDRD = 0xff;
// ------ Event loop ------ //
while (1) {
while (i < 7) {
LED_PORTB = (1 << i); /* illuminate only i'th pin */
LED_PORTD = (1 << j);
_delay_ms(DELAYTIME); /* wait */
i = i + 1; /* move to the next LED */
j = i;
}
while (i > 0) {
LED_PORTB = (1 << i); /* illuminate only i'th pin */
LED_PORTD = (1 << j);
_delay_ms(DELAYTIME); /* wait */
i = i - 1; /* move to the previous LED */
j = i;
}
} /* End event loop */
return (0);
}
// Example 4-1. cylonEyes.c modified listing 3
// ------- Preamble -------- //
#include <avr/io.h> /* Defines pins, ports, etc */
#include <util/delay.h> /* Functions to waste time */
#define DELAYTIME 1000 /* milliseconds */
#define LED_PORTB PORTB
#define LED_PINB PINB
#define LED_DDRB DDRB
#define LED_PORTD PORTD
#define LED_PIND PIND
#define LED_DDRD DDRD
int main(void) {
// -------- Inits --------- //
uint8_t i = 0;
uint8_t j = 7;
LED_DDRB = 0xff; /* Data Direction Register B: all set up for output */
LED_DDRD = 0xff;
// ------ Event loop ------ //
while (1) {
while ((i < 7)&&(j > 0)) {
LED_PORTB = (1 << i); /* illuminate only i'th pin */
LED_PORTD = (1 << j);
_delay_ms(DELAYTIME); /* wait */
i = i + 1; /* move to the next LED */
j = j - 1;
}
while ((i > 0)&&(j < 7)) {
LED_PORTB = (1 << i); /* illuminate only i'th pin */
LED_PORTD = (1 << j);
_delay_ms(DELAYTIME); /* wait */
i = i - 1; /* move to the previous LED */
j = j + 1;
}
} /* End event loop */
return (0);
}
