Arduino file for reading temperature and displaying on LCD

TempLCD.ino

/*
  TempLcd.ino
  2017 Copyright (c) Koen Hendriks.  All right reserved.
  
  Connect LCD:
  VCC : 5v
  GND : GND
  SDA : A4 Arduino
  SCL : A5 Arduino
  
  Connect Temperature Sensor,
  Flat side down, left to right:
  (left)   GND : GND
  (middle) SCL : A0 Arduino
  (right)  VCC : 5v  
  
  Button : Digital 4 Arduino
  
*/

#include <Wire.h>
#include "rgb_lcd.h"

rgb_lcd lcd;

const int colorR = 118;
const int colorG = 232;
const int colorB = 220;

int TsensorPin = A0;
int buttonPin = 4;
int ledPin = 13;          
int loops = 0;          
boolean screenOn = true;
double temperature = 0.0;
int totalTemperature = 0;
int avegareTemp = 0;

void setup() 
{
    // set up the LCD's number of columns and rows
    lcd.begin(16, 2);
    
    // set up the LCD default text
    lcd.print("Welkom bij Koen!"); 
    lcd.setCursor(0,1);
    
    // Background color
    lcd.setRGB(colorR, colorG, colorB);

    // Set Pins
    pinMode(TsensorPin, INPUT);                   
    pinMode(ledPin, OUTPUT);  
    pinMode(buttonPin, INPUT);  
}

void loop() 
{      
    loops++;
    temperature = TMP36GT_AI_value_to_Celsius(analogRead(TsensorPin));
    totalTemperature += temperature;
    avegareTemp = totalTemperature / loops;
    
    //Start displaying on second row
    lcd.setCursor(0,1);
  
    // Cast to int for rounded number
    int lastMeasure = (int) temperature;
    lcd.print("T:");
    lcd.print(lastMeasure);
    lcd.print("C");
  
    // Cast to int for rounded number  
    int temp = (int) avegareTemp;
    
    // Set cursor to align left
    lcd.setCursor(8,1);
    lcd.print("Gem: ");
    lcd.print(temp);
    lcd.print("C");
    if(digitalRead(buttonPin)){
        onButtonPress();
    }    
    delay(1000);
}

void onButtonPress(){
    if(screenOn){
      lcd.noDisplay();
      lcd.setRGB(0,0,0);
      screenOn = false;
    }else{
      lcd.display();  
      lcd.setRGB(colorR, colorG, colorB);
      screenOn = true;
    }
  
}

double TMP36GT_AI_value_to_Celsius(int AI_value)
{                                               
    float voltage;
    voltage = AI_value * (5000.0/1024);  
    // Temperature according to datasheet: 750 mV = 25 °C    
    return ((voltage -750) /10) +25;                

}