int STROBE       = 9; // latch
int DATAOUT      = 10;
int DATAOUT17BIT = 12; // we only use two shift regs for 16 bits. for 17th bit, we use digital out
int CLOCK        = 11;

int DATAINWIDTH  = 8;
int DATAINPINS[] = {2,3,4,5,6,7,8,13};

int addr  = 0;
int input = 0;

void sendDataOut(int value) {
  shiftOut(DATAOUT, CLOCK, LSBFIRST, (value & 0x000FF) ); //first byte
  shiftOut(DATAOUT, CLOCK, LSBFIRST, (value & 0x0FF00) ); //second byte
  // We only have two shift regs so to deal with the 17th bit:
  digitalWrite(DATAOUT17BIT,         (value & 0x10000) ); //highest bit
  
  // LATCH:
  digitalWrite(STROBE, HIGH);
  delayMicroseconds(10);
  digitalWrite(STROBE, LOW);
}
int readDataIn() {
    int ret = 0x00000;
    int in = 0;
    for (int i=0; i<DATAINWIDTH; i++) {
        if( digitalRead(DATAINPINS[i]) == HIGH) {
                ret |= (1<<i);
        }
        // DEBUG:
        //Serial.print( digitalRead(DATAINPINS[i]));
        //Serial.print(" ");
    }
    // Debug
    //Serial.print("\n");    
    return ret;
}

void setup (void) {
        pinMode(STROBE, OUTPUT);
        pinMode(CLOCK,  OUTPUT);
        // out
        pinMode(DATAOUT,OUTPUT);
        pinMode(DATAOUT17BIT,OUTPUT);
        // in
        for (int i=0; i<DATAINWIDTH; i++) {
                pinMode(DATAINPINS[i], INPUT);
        }
                
        Serial.begin(9600);
}


void loop (void) {

  for ( addr = 0; addr<=0x1FFFF; addr++) {
    sendDataOut(addr);
    input = readDataIn();
    Serial.print(addr, BIN);
    Serial.print(": ");
    Serial.print(input, BIN);
    Serial.print("\n");
    delay(1000);
  }
}





/* OLD CODE:

void sendByteOut(int value) {
  shiftOut(DATAOUT, CLOCK, LSBFIRST, value);
  digitalWrite(STROBE, HIGH);
  delayMicroseconds(10);
  digitalWrite(STROBE, LOW);
}
void sendWordOut(int value) {
  shiftOut(DATAOUT, CLOCK, LSBFIRST, value);
  shiftOut(DATAOUT, CLOCK, LSBFIRST, (value>>8));
  digitalWrite(STROBE, HIGH);
  delayMicroseconds(10);
  digitalWrite(STROBE, LOW);
}

*/