https://medium.com/jungletronics/arduino-multi-file-sketch-583a7833162c Arduino Multi File Sketch

_45_working_w_MultiFile_Sketch_03.ino

/* Project Ardu_Serie # 45
   Working w/ MultiFile Sketch - Part III - Atmega328p IC - Arduino MC
   Ino File: _45_working_w_MultiFile_Sketch_03.ino   
*/

#include <LiquidCrystal.h>
#include <DFR_LCD_Keypad.h>             //Sample using https://www.dfrobot.com library

                                        // select the pins used on the LCD panel
LiquidCrystal lcd(8, 9, 4, 5, 6, 7);
                                        // initialise the keypad
DFR_LCD_Keypad keypad(A0, &lcd);

#include "HC_SR04.h"                    // Warning: this headers should come after the lcd boot
#include "PIR.h"

                                        // define the key used by the panel and buttons
int key;

                                        // LM35 variables
float tempC;
int reading;
int tempPin = 1;
                                        //custom degree character
byte degree[8] = {
  B00110,
  B01001,
  B01001,
  B00110,
  B00000,
  B00000,
  B00000,
  B00000,
};


void setup()
{                                       //LCD setup
  lcd.createChar(0, degree);
  lcd.begin(16, 2);                     // start the library
  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("Push the buttons");        // print a simple message

  HC.HC_Setup(11, 12);
  PIR.PIR_Setup(13, 2, HIGH);

}

void loop()
{
  PIR.PIR_Loop();
  lcd.setCursor(0, 1);                  // move to the begining of the second line
  key = keypad.read_key();              // read the buttons
                                        // print the key selection to the LCD
  switch (key)                          // depending on which button was pushed, we perform an action
  {

    case KEY_RIGHT:
      {
       PIR.PIR_Display();
        break;
      }
      
     case KEY_LEFT:
      {
        HC.HC_Loop();
        HC.HC_Display();
        break;
      }
      
    case KEY_DOWN:
      { 
        reading = analogRead(tempPin);
        lcd.setCursor(0, 1);                  // move to the begining of the second line                                            
        float voltage = reading * 5.0;        // converting that reading to voltage
        voltage /= 1024.0;
                                            // now print out the temperature
        tempC = (voltage - 0.5) * 100 ;      //converting from 10 mv per degree wit 500 mV offset
                                            //to degrees ((voltage - 500mV) times 100)
        lcd.print(tempC, 1);
        lcd.setCursor(4, 2);                  // move cursor to second line "1" and 4 spaces over
        lcd.write((byte)0);                   // display custom degree symbol
        lcd.print("C");
        delay(100);     
        break;
      }
         
    case KEY_SELECT:
      {
        lcd.print("Thank you!I'm J3");
        break;
      }
   
    case KEY_NONE:
      {
        lcd.print("                ");
        break;
      }
  }

}