byte digits[] = {0x7e, 0x30, 0x6d, 0x79, 0x33, 0x5b, 0x5f, 0x70, 0x7f, 0x7b, 0x77, 0x1f, 0x4e, 0x3d, 0x4f, 0x47};
byte cathodePins[] = {0x70, 0xb0, 0xd0, 0xe0};
//74hc165 connections
int SH_LD = 2;
int CLK = 3;
int CE = 4;
int QH = 5;
//74hc595 connections
int dataPin = 6;
int clockPin = 7;
int latchPin = 8;

int switchPin1 = 9;
int switchPin2 = 10;


void setup() {
  // put your setup code here, to run once:
  pinMode(SH_LD, OUTPUT);
  pinMode(CLK, OUTPUT);
  pinMode(CE, OUTPUT);
  pinMode(QH, INPUT );
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(switchPin1, INPUT);
  pinMode(switchPin2, INPUT);
}

void loop() {
   // 2's complement mode
   if(digitalRead(switchPin2) == HIGH && digitalRead(switchPin1) == HIGH){

      int val = readInput();
        if(val <= 127){
           val = val;
           printDigits(val, 10);
        }
          if(val > 127){
            val = (val - 128) - 128;
            printDigits(val, 10);
          }
   }
   //decimal mode
   else if(digitalRead(switchPin2) == LOW && digitalRead(switchPin1) == LOW){

      printDigits(readInput(), 10);
   }
   // hexadecimal mode
   else if(digitalRead(switchPin2) == LOW && digitalRead(switchPin1) == HIGH){
      
      printDigits(readInput(), 16);
   }
   // octal mode
   else if(digitalRead(switchPin2) == HIGH && digitalRead(switchPin1) == LOW){
      
      printDigits(readInput(), 8);
   }
}
void printDigits(int num, int base){
   
    if(abs(num)>=0 && abs(num) <= 9){
       digitalWrite(latchPin, LOW);
       shiftOut(dataPin, clockPin, MSBFIRST, digits[abs(num) % base]);
       shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[0]);
       digitalWrite(latchPin, HIGH);
       delay(33);
         if(num < 0){
            digitalWrite(latchPin, LOW);
            shiftOut(dataPin, clockPin, MSBFIRST, 0x01);
            shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[1]);
            digitalWrite(latchPin, HIGH);
            delay(33);
         }
         if(base == 8 && num == 8){
            digitalWrite(latchPin, LOW);
            shiftOut(dataPin, clockPin, MSBFIRST, digits[(abs(num)/base) % base]);
            shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[1]);
            digitalWrite(latchPin, HIGH);
            delay(33);
         }
         else{
           digitalWrite(latchPin, LOW);
           shiftOut(dataPin, clockPin, MSBFIRST, 0x00);
           shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[1]);
           digitalWrite(latchPin, HIGH);
           delay(33);
         }
    }
    if(abs(num) > 9 && abs(num) <= 99){
        digitalWrite(latchPin, LOW);
        shiftOut(dataPin, clockPin, MSBFIRST, digits[abs(num) % base]);
        shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[0]);
        digitalWrite(latchPin, HIGH);
        delay(33);
        digitalWrite(latchPin, LOW);
        shiftOut(dataPin, clockPin, MSBFIRST, digits[(abs(num)/base) % base]);
        shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[1]);
        digitalWrite(latchPin, HIGH);
        delay(33);
          if(num < 0){
            digitalWrite(latchPin, LOW);
            shiftOut(dataPin, clockPin, MSBFIRST, 0x01);
            shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[2]);
            digitalWrite(latchPin, HIGH);
            delay(33);
          }
          else{
            digitalWrite(latchPin, LOW);
            shiftOut(dataPin, clockPin, MSBFIRST, 0x00);
            shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[2]);
            digitalWrite(latchPin, HIGH);
            delay(33);
          }
    }

    if(abs(num) > 99 && abs(num) < 256){
       digitalWrite(latchPin, LOW);
       shiftOut(dataPin, clockPin, MSBFIRST, digits[abs(num) % base]);
       shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[0]);
       digitalWrite(latchPin, HIGH);
       delay(33);
       digitalWrite(latchPin, LOW);
       shiftOut(dataPin, clockPin, MSBFIRST, digits[(abs(num)/base) % base]);
       shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[1]);
       digitalWrite(latchPin, HIGH);
       delay(33);
       digitalWrite(latchPin, LOW);
       shiftOut(dataPin, clockPin, MSBFIRST, digits[(abs(num)/(base*base)) % base]);
       shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[2]);
       digitalWrite(latchPin, HIGH);
       delay(33);
         if(num < 0){
           digitalWrite(latchPin, LOW);
           shiftOut(dataPin, clockPin, MSBFIRST, 0x01);
           shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[3]);
           digitalWrite(latchPin, HIGH);
           delay(33);
         }
         else{
           digitalWrite(latchPin, LOW);
           shiftOut(dataPin, clockPin, MSBFIRST, 0x00);
           shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[3]);
           digitalWrite(latchPin, HIGH);
           delay(33);
         }
    }
  }
/*
void printDigits(int num, int base){

    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, MSBFIRST, digits[abs(num) % base]);
    shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[0]);
    digitalWrite(latchPin, HIGH);
    delay(33);
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, MSBFIRST, digits[abs(num/base) % base]);
    shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[1]);
    digitalWrite(latchPin, HIGH);
    delay(33);
    if(base == 16){
       digitalWrite(latchPin, LOW);
       shiftOut(dataPin, clockPin, MSBFIRST,0x00);
       shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[2]);
       digitalWrite(latchPin, HIGH);
       delay(33);
    }
    else{
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, MSBFIRST, digits[abs(num/(base * base)) % base]);
    shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[2]);
    digitalWrite(latchPin, HIGH);
    delay(33);
    }
     digitalWrite(latchPin, LOW);

       if(num < 0){
          shiftOut(dataPin, clockPin, MSBFIRST, 0x01);
          shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[3]);
        }
        else{
           shiftOut(dataPin, clockPin, MSBFIRST, 0x00);
           shiftOut(dataPin, clockPin, MSBFIRST, cathodePins[3]);
        }
     digitalWrite(latchPin, HIGH);
    delay(33);

}*/

int readInput(){
  digitalWrite(SH_LD, LOW);
  delayMicroseconds(5);
  digitalWrite(SH_LD, HIGH);
  delayMicroseconds(5);
  
  digitalWrite(CLK, HIGH);
  digitalWrite(CE, LOW);

  int data = shiftIn(QH, CLK, MSBFIRST);

  digitalWrite(CE, HIGH);
  return data;
delay(200);
}