7-segment numeric display

/* 
Basic ver 3 demo program
7-seg function and demo
Raivo Sell/Erki Leitaru
*/
#define F_CPU 14745600UL
 
#include <avr/io.h>
#include <util/delay.h>
 
#define SET(x) |= (1<<x)  //defineeritakse kõrge bit pordis x
#define CLR(x) &=~(1<<x)  //defineeritakse madal bit pordis x
#define bit_get(p,m) ((p) & (m)) //returns 1 if bit is set, otherwise returns 0
#define BIT(x) (0x01 << (x))
 
void write_display (void);
void nop_delay(int count);
 
int i;//for cycle
int digit;//digit to display on segment
int nr;//segment map representation of the digit
int delta;//to create a counting effect
int num = 0;
char buffer[7];
 
void nop_delay(int count){
	unsigned int j;
	for (j=0; j<count;j++)	{asm volatile ("nop");}
}
 
void write_display (void) {
	 switch (digit) //table read to get segment map representation of the digit
	 {
		 case 0 : nr = 0b00111111;break; //every bit corresponds to one segment
		 case 1 : nr = 0b00000110;break; //"1"
		 case 2 : nr = 0b01011011;break; //"2" and so on
		 case 3 : nr = 0b01001111;break; 
		 case 4 : nr = 0b01100110;break; 
		 case 5 : nr = 0b01101101;break; 
		 case 6 : nr = 0b01111100;break; 
		 case 7 : nr = 0b00000111;break;
		 case 8 : nr = 0b01111111;break; 
		 case 9 : nr = 0b01100111;break;  
		 default: nr = 0b01111001;//E
	 }
 
	 PORTG CLR (2); //latch low
	 for(i=7; i>=0; i--) //for every bit in the byte
	 {
	 	//if bit is set, sets the data out pin
		if (bit_get(nr, BIT(i))) PORTC SET (6); //serial out
		else PORTC CLR (6); //serial out
 
		PORTC SET (7); //clock high
		nop_delay(8);//series of one cycle delays to ensure required timing (according to datasheet)
 
		PORTC CLR (7); //clock low
		nop_delay(8);
	 }
	 PORTG SET (2); //latch high
 
}
 
int main(void){
 
	//7-seg init
    PORTC = 0xFF; // set output high -> turn all LEDs off
    DDRC  = 0xF8; // PC0...PC2 -> input; PC3...PC5 -> output for LED; PC7 & PC6 outputs for clock and data
	DDRG  = 0x04;//PG2 is latch output
 
	digit = 8;
	delta = 1;//increment or decrement
 
	while(1) {
		num++;
		_delay_ms(1000);
		digit=digit+delta;//change digit by delta
		if(digit>8) {delta=-1*delta;};//upper limit
		if(digit<1) {delta=-1*delta;};//lower limit
		write_display();
	}
}

this example does not contain global variables and only functions are used. It is more easy to copy the functions into user program. All variables are 8 bit where possible.

//
// Simple up/down counting single 7-segment digit example.
//
// Raivo Sell, Erki Leitaru, Mikk Leini
//
// 2009
//
#define F_CPU 14745600UL
 
// Include avrlibc
#include <avr/io.h>
#include <util/delay.h>
 
// Macros for bit manipulation
#define BIT(x) (1 << (x))
#define SET(x) |=  BIT(x)
#define CLR(x) &= ~BIT(x)
#define SETTO(value, bit, to) value = ((to) ? value | BIT(bit) : value & ~BIT(bit)) 
#define ISSET(value, bit) ((value) & (BIT(bit)))
 
//
// Delay cycle
// On each cycle "no-operation" instruction is executed
//
void nop_delay(unsigned int count)
{	
	for (unsigned int i = 0; i < count; i++)
	{
		asm volatile ("nop");
	}
}
 
//
// 7 segment display initialization
//
void segment_diplay_init(void)
{
	// Port C pin 7 - clock output, pin 6 data output
	DDRC |= 0xC0; 
 
	// Port G pin 2 - latch output 	
	DDRG |= 0x04;
}
 
//
// Digit writing to 7 segment display
//
void segment_display_write(unsigned char digit)
{
	unsigned char map;
 
	// Decimal to segment map
	switch (digit)
	{
		case 0 : map = 0b00111111; break; // Every bit corresponds to one segment
		case 1 : map = 0b00000110; break; // "1"
		case 2 : map = 0b01011011; break; // "2"
		case 3 : map = 0b01001111; break; // "3" and so on
		case 4 : map = 0b01100110; break; 
		case 5 : map = 0b01101101; break; 
		case 6 : map = 0b01111100; break; 
		case 7 : map = 0b00000111; break;
		case 8 : map = 0b01111111; break; 
		case 9 : map = 0b01100111; break;  
		default: map = 0b01111001;        // E like Error
	}
 
	// Latch low
	PORTG CLR(2);
 
	// Send every bit in the byte. MSB (most significant bit) first.
	for (signed char i = 7; i >= 0; i--)
	{
		// If bit is set, sets the data out pin, otherwise not
		SETTO(PORTC, 6, ISSET(map, i));
 
		// Clock high for certain period
		PORTC SET(7); 
		nop_delay(8);
 
		// Clock low for certain period
		PORTC CLR(7);
		nop_delay(8);
	}
 
	// Latch high 
	PORTG SET(2); 
}
 
//
// Program entrance function
//
int main(void)
{ 
	unsigned char digit = 0; // Digit to display on segment
	signed char delta = 1;   // Digit modifying value
 
	// 7 segment display initialization
	segment_diplay_init();	 
 
 	// Endless loop
	while (1)
	{				
		// Write digit
		segment_display_write(digit);
 
		// Increase digit value by delta (which can be negative also)
		digit += delta;
 
		// Swap counting direction on 0 and 9
		if (digit == 0) delta = +1;
		if (digit == 9) delta = -1;		
 
		// Wait 1000 ms
		_delay_ms(1000);
	}
}

“pinops.h” library is used to simplify the port and pin usage. See here for more detail description.

LED driver is replaced by the avrlibc driver.

//
// Simple up/down counting single 7-segment digit example.
//
// Raivo Sell, Erki Leitaru, Mikk Leini
//
// 2009
//
 
// Include avrlibc
#include <avr/io.h>
#include <util/delay.h>
 
// Include common library
#include "pinops.h"
 
/* PS! For distance Lab use:
#include <util/pinops.h>
*/
 
// Configure pins
#define SEGMENT_DISPLAY_LATCH      PORTPIN(G, 2)
#define SEGMENT_DISPLAY_DATA_OUT   PORTPIN(C, 6)
#define SEGMENT_DISPLAY_CLOCK      PORTPIN(C, 7)
 
//
// 7 segment display initialization
//
void segment_display_init(void)
{
	// Set latch, data out and clock pins as output
	setup_output_pin(SEGMENT_DISPLAY_LATCH);
	setup_output_pin(SEGMENT_DISPLAY_DATA_OUT);
	setup_output_pin(SEGMENT_DISPLAY_CLOCK);	
}
 
//
// Digit writing to 7 segment display
//
void segment_display_write(unsigned char digit)
{
	unsigned char map;
 
	// Decimal to segment map
	switch (digit)
	{
		case 0 : map = 0b00111111; break; // Every bit corresponds to one segment
		case 1 : map = 0b00000110; break; // "1"
		case 2 : map = 0b01011011; break; // "2"
		case 3 : map = 0b01001111; break; // "3" and so on
		case 4 : map = 0b01100110; break; 
		case 5 : map = 0b01101101; break; 
		case 6 : map = 0b01111100; break; 
		case 7 : map = 0b00000111; break;
		case 8 : map = 0b01111111; break; 
		case 9 : map = 0b01100111; break;  
		default: map = 0b01111001;        // E like Error
	}	
 
	// Latch low
	clear_pin(SEGMENT_DISPLAY_LATCH);
 
	// Send every bit in the byte. MSB (most significant bit) first.
	for (signed char i = 7; i >= 0; i--)
	{
		// If bit is set, sets the data out pin, otherwise not		
		set_pin_to(SEGMENT_DISPLAY_DATA_OUT, IS_BIT_SET(map, i));
 
		// Clock high for certain period
		set_pin(SEGMENT_DISPLAY_CLOCK)
		_delay_us(1);
 
		// Clock low for certain period		
		clear_pin(SEGMENT_DISPLAY_CLOCK)
		_delay_us(1);
	}
 
	// Latch high 	
	set_pin(SEGMENT_DISPLAY_LATCH);
}
 
//
// Program entrance function
//
int main(void)
{ 
	unsigned char digit = 0; // Digit to display on segment
	signed char delta = 1;   // Digit modifying value
 
	//digit = int (void) { return 2; }; 
 
	// 7 segment display initialization
	segment_display_init();	 
 
 	// Endless loop
	while (1)
	{
		// Write digit
		segment_display_write(digit);
 
		// Increase digit value by delta (which can be negative also)
		digit += delta;
 
		// Swap counting direction on 0 and 9
		if (digit == 0) delta = +1;
		if (digit == 9) delta = -1;		
 
		// Wait 1000 ms
		_delay_ms(1000);
	}
}