#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C LCD = LiquidCrystal_I2C(0x27, 20, 4);

#define dataPin 2   /* Q7 */
#define clockPin 3  /* CP */
#define latchPin 4  /* PL */
const int numBits = 24;   /* Set to 8 * number of shift registers */
byte pulseWidth = 2;
long oldOptionSwitch;
long keyValue;
 long optionSwitch = 0;

byte ReadOne165()
{
  byte ret = 0x00;
  // The first one that is read is the highest bit (input D7 of the 74HC165).
  for( int i=7; i>=0; i--)
  {
    if( digitalRead( dataPin) == HIGH)
      bitSet( ret, i);
     digitalWrite( clockPin, HIGH);
     delayMicroseconds( pulseWidth);
     digitalWrite( clockPin, LOW);
    }
  return( ret);
}

int getKey(void){
long optionSwitch = 0;
  for( int i=24; i>=0; i-=8)
  {
    optionSwitch |= ((uint32_t) ReadOne165()) << i;
  }
 for( int i = 0; i<32; i++)
  {
    if( bitRead( optionSwitch, i) != bitRead( oldOptionSwitch,i))
    {
      Serial.print( "Switch ");
      if( i < 10)
        Serial.print( " ");
      Serial.print( i);
      Serial.print( " is now ");
      Serial.println( bitRead( optionSwitch, i) == 0 ? "down ↓" : "up   ↑");
    }
  }
  oldOptionSwitch = optionSwitch;
  delay(25);      // slow down the sketch to avoid switch bounce
}

void setup() {
  Serial.begin(115200);
  pinMode(dataPin, INPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  LCD.init();
  LCD.backlight();
  LCD.setCursor(0, 0);
  LCD.print("Button Test ");
  }

void loop() {
 long keyValue = getKey();
 Serial.print(keyValue,DEC);
 LCD.setCursor(0, 1);
 LCD.print(keyValue,DEC);
}