/*Define shift register pins used for seven segment display */

#define LATCH_DIO 4

#define CLK_DIO 7

#define DATA_DIO 8

/* Segment byte maps for numbers 0 to 9 */

const byte SEGMENT_MAP[] ={0xC0,0xF9,0xA4,0xB0,0x99,0x92,0x82,0xF8,0x80,0x90} ;

/* Byte maps to select digit 1 to 4 */

const byte SEGMENT_SELECT[] ={0xF1,0XF2,0XF4,0XF8};

void setup ()

{

/* Set DIO pins to outputs */

pinMode (LATCH_DIO,OUTPUT);

pinMode (CLK_DIO,OUTPUT) ;

pinMode (DATA_DIO,OUTPUT) ;

}

/* Main program */

void loop()

{

/* Update the display with the current counter value */

WriteNumberToSegment(0,0);

WriteNumberToSegment(1,1);

WriteNumberToSegment(2,2);

WriteNumberToSegment(3,3);

}

/* Write a decimal number between O and 9 to one of the 4 digits of the display */

void WriteNumberToSegment(byte Segment, byte Value)

{

digitalWrite(LATCH_DIO,LOW);

shiftOut(DATA_DIO, CLK_DIO, MSBFIRST, SEGMENT_MAP[Value]);

shiftOut(DATA_DIO, CLK_DIO, MSBFIRST, SEGMENT_SELECT[Segment] );

digitalWrite(LATCH_DIO,HIGH);

}