#include <SPI.h>
#include <TimerOne.h>

const byte seg7_digit[10]={
 //abcdefgh 
  B11111100, //數字0
  B01100000, //數字1
  B11011010,
  B11110010,
  B01100110,
  B10110110,
  B10111110,
  B11100100, //7
  B11111110, //8
  B11110110};


#define SS 10 

volatile int number = 0;
volatile bool chang = true;

void setup() {
 
  pinMode(SS, OUTPUT);
  digitalWrite(SS, HIGH);

  SPI.begin();

  Timer1.initialize(1000000); 
  Timer1.attachInterrupt(A123);

}

void loop() {
 
}

void A123() {

  digitalWrite(SS, LOW);     
  SPI.transfer(seg7_digit[number]); 
  digitalWrite(SS, HIGH);     

    number += chang ? 1 : -1; 
  if (number == 9 || number == 0) {
    chang = !chang; 
 }
}