====== 7-Segment-Anzeige ======

{{:examples:7-seg.jpg|}}

Das Study Board ist meiner einer 7-Segment LED Anzeige und dem entsprechendem Treiber (A6275) ausgestattet.
({{:examples:datasheets:a6275_led_driver.pdf|datasheet}}).
Der Treiber ist an PORT-C und PORT-G des Controllers angeschlossen.

Der Schaltplan zeigt: Das Auffangregister (latch) liegt an PORT-G2, Serial an PORT-C6 und Clock an PORT-C7.

{{:examples:7seg_schematics.jpg?500}}


===== Beispiel 1 =====

<code c>
/* 
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();
	}
}

</code>

===== Beispiel 2 =====

Dieses Bsp. nutzt die Header Datei pin.h für Pin-Operationen [[en:examples:digi:pin|"pin.h"]]

<code c>
//
// 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 "pin.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
	pin_setup_output(SEGMENT_DISPLAY_LATCH);
	pin_setup_output(SEGMENT_DISPLAY_DATA_OUT);
	pin_setup_output(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
	pin_clear(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		
		pin_set_to(SEGMENT_DISPLAY_DATA_OUT, IS_BIT_SET(map, i));

		// Clock high for certain period
		pin_set(SEGMENT_DISPLAY_CLOCK)
		_delay_us(1);

		// Clock low for certain period		
		pin_clear(SEGMENT_DISPLAY_CLOCK)
		_delay_us(1);
	}

	// Latch high 	
	pin_set(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);
	}
}
</code>

===== Externe Links =====
[[http://en.wikipedia.org/wiki/Seven-segment_display|7-segment display in Wikipedia]]