// NOTE: DEMO ONLY!!
// Each LED segment should be current limited with a 220ohm resistor
// The clock pin of the shift registers (SHCP) must be connected to
// the GND via a 100nF ceramic capacitor

#include <Button.h>

int compareMatchReg;
volatile int interrupts;

int latchPin = 8;//Pin connected to ST_CP of each shift register
int clockPin = 12;  //Pin connected to SH_CP of each shift register
int dataPin = 11; //Pin connected to DS of first shift register
// Connect Q7S of the first shift register to DS of the next register(s)
Button btnUp(A0);
Button btnDown(A1);

byte arrNums[] = {
  B11111100,B01100000,B11011010,
  B11110010,B01100110,B10110110,
  B10111110,B11100000,B11111110,
  B11110110};
byte blank = B11111111;

// Set initial digit values here,
// Could probably break this up into array once passed as a 5 digit number
int n1 = 1;
int n2 = 9;
int n3 = 8;
int n4 = 6;
int s1 = 0;
 
void setup() 
{
  Serial.begin(9600);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(A0, INPUT_PULLUP);
  pinMode(A1, INPUT_PULLUP);
  btnUp.begin();
  btnDown.begin();

  //  Set up timer interrupts to keep the LED segments lit up
	noInterrupts();           // disable all interrupts
	TCCR1A = 0;
	TCCR1B = 0;
	compareMatchReg = 15624;   // preload timer from calc above
	TCNT1 = compareMatchReg;   // preload timer
	TCCR1B |= (1 << CS11 + CS10);    // 256 prescaler 
	TIMSK1 |= (1 << TOIE1);   // enable timer overflow interrupt
	interrupts();             // enable all interrupts
}

ISR(TIMER1_OVF_vect)        // interrupt service routine 
{
	TCNT1 = compareMatchReg;   // preload timer
	interrupts++;

  // Refresh each digit in the 4 digit LED
  // Uses persistence of vision, in fact it is updating
  // each digit so fast the eyes don't see it blink
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, 128);
  shiftOut(dataPin, clockPin, LSBFIRST, ~arrNums[n1]);
  shiftOut(dataPin, clockPin, LSBFIRST, arrNums[s1]);
  digitalWrite(latchPin, HIGH);

    digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, 64);
  shiftOut(dataPin, clockPin, LSBFIRST, ~arrNums[n2]);
  shiftOut(dataPin, clockPin, LSBFIRST, arrNums[s1]);
  digitalWrite(latchPin, HIGH);
  
    digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, 32);
  shiftOut(dataPin, clockPin, LSBFIRST, ~arrNums[n3]);
  shiftOut(dataPin, clockPin, LSBFIRST, arrNums[s1]);
  digitalWrite(latchPin, HIGH);
  
    digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, 16);
  shiftOut(dataPin, clockPin, LSBFIRST, ~arrNums[n4]);
  shiftOut(dataPin, clockPin, LSBFIRST, arrNums[s1]);
  digitalWrite(latchPin, HIGH);

}


void loop(){
  if(btnUp.pressed()){
    n4++;
  }
  if(btnDown.pressed()){
    n4--;
  }
n4 = constrain(n4,0,9);
}