void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

}

void setRegOne(uint8_t value) {
  // close all registers
  digitalWrite(10, LOW);
  digitalWrite(11, LOW);
  digitalWrite(12, LOW);
  digitalWrite(13, LOW);

  // Shift and extract bit to get bits
  int d0 = value & 0b00000001; 
  int d1 = (value >> 1) & 0b00000001; 
  int d2 = (value >> 2) & 0b00000001;
  int d3 = (value >> 3) & 0b00000001;
  int d4 = (value >> 4) & 0b00000001; 
  int d5 = (value >> 5) & 0b00000001; 
  int d6 = (value >> 6) & 0b00000001; 
  int d7 = (value >> 7) & 0b00000001; 

  delay(10);

  // Set pin values
  digitalWrite(2,d0);
  digitalWrite(3,d1);
  digitalWrite(4,d2);
  digitalWrite(5,d3);
  digitalWrite(6,d4);
  digitalWrite(7,d5);
  digitalWrite(8,d6);
  digitalWrite(9,d7);

  delay(10);

  // instruction: open register 1 to accept data
  digitalWrite(11, HIGH);

  delay(10);

  // close register 1
  digitalWrite(11, LOW);

  delay(10);

  // set pins back to LOW
  for (int pinNum = 2; pinNum < 10; pinNum++) {
    digitalWrite(pinNum, LOW);
  }
  delay(10);
}


// note: will mess up registers 3 and 4
void copyToRegTwo() {
  // close all registers
  digitalWrite(10, LOW);
  digitalWrite(11, LOW);
  digitalWrite(12, LOW);
  digitalWrite(13, LOW);

  delay(10);

  // Instruction: copy from reg 1 to reg 2
  digitalWrite(10, HIGH);
  digitalWrite(11, HIGH);
  digitalWrite(12, LOW);
  digitalWrite(13, LOW);

  delay(10);

  // close all registers
  digitalWrite(11, LOW);
  digitalWrite(10, LOW);
  delay(10);
}


void readToReg4() {
  // close all registers
  digitalWrite(10, LOW);
  digitalWrite(11, LOW);
  digitalWrite(12, LOW);
  digitalWrite(13, LOW);

  delay(10);

  // Instruction: read from reg 3 to reg 4
  digitalWrite(10, HIGH);

  delay(10);

  // close all registers
  digitalWrite(10, LOW);
  delay(10);
}

uint8_t readFromReg4() {
  // close all registers
  digitalWrite(10, LOW);
  digitalWrite(11, LOW);
  digitalWrite(12, LOW);
  digitalWrite(13, LOW);

  delay(10);

  // Read from reg 4
  uint8_t q0 = digitalRead(A0);
  uint8_t q1 = (digitalRead(A1) << 1);
  uint8_t q2 = (digitalRead(A2) << 2);
  uint8_t q3 = (digitalRead(A3) << 3);
  uint8_t q4 = (digitalRead(A4) << 4);
  uint8_t q5 = (digitalRead(A5) << 5);
  uint8_t q6 = (digitalRead(A6) << 6);
  uint8_t q7 = (digitalRead(A7) << 7);
  delay(10);

  return (q0 + q1 + q2 + q3 + q4 + q5 + q6 + q7);
}




uint8_t add(uint8_t num2, uint8_t num1) {
  setRegOne(num2);
  copyToRegTwo();
  setRegOne(num1);

  // instruction: add reg 1 to reg 2
  digitalWrite(10, LOW);
  digitalWrite(13, HIGH);
  digitalWrite(12, HIGH);
  digitalWrite(11, HIGH);

  // Delay for register 3 to read
  delay(2);
  
  
  // close registers
  digitalWrite(10, LOW);
  digitalWrite(11, LOW);
  digitalWrite(12, LOW);
  digitalWrite(13, LOW);
  delay(2);

  // read to register 4
  readToReg4();

  return readFromReg4();
}