Modifying the code to work with a LCD I2C

Hello,

I'm currently trying to control a stepper motor using a 3x4 keypad and a LCD I2C. I've already found a similiar code on the internet which im trying to modify to work with my application. But i'm having trouble converting the code to work with my LCD I2C.

The LCD im using:
20x4 LCD Wit op Blauw 5V - I2C | Klanten beoordelen ons met een 9/10! (elektronicavoorjou.nl)

The keypad im using:
3X4 Matrix keypad - Zwart | Voor 16:00 besteld = morgen in huis! (elektronicavoorjou.nl)

What im trying to achieve:
I want to modify the code so i can use a 20x4 LCD I2C. The existing code is using a U8glib for nokia LCD
This video will further illustrate what im trying to create:

The existing code:

/* Arduino Control Stepper with Keypad and LCD

Created by Yvan / https://Brainy-Bits.com
This code is in the public domain...
You can: copy it, use it, modify it, share it or just plain ignore it!
Thx!

*/

#include "AccelStepper.h" // AccelStepper Library
#include <Keypad.h>  // Keypad Library
#include "U8glib.h"  // U8glib for Nokia LCD

// Variables to hold entered number on Keypad
volatile int firstnumber=99;  // used to tell how many numbers were entered on keypad
volatile int secondnumber=99;
volatile int thirdnumber=99;

// Variables to hold Distance and CurrentPosition
int keyfullnumber=0;  // used to store the final calculated distance value
String currentposition = "";  // Used for display on Nokia LCD


// Keypad Setup
const byte ROWS = 4; // Four Rows
const byte COLS = 3; // Four Columns
char keys[ROWS][COLS] = {
  {'1','2','3'},
  {'4','5','6'},
  {'7','8','9'},
  {'*','0','#'}
};
byte rowPins[ROWS] = {22, 24, 26, 28}; // Arduino pins connected to the row pins of the keypad
byte colPins[COLS] = {31, 33, 35}; // Arduino pins connected to the column pins of the keypad
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );  // Keypad Library definition


// U8glib Setup for Nokia LCD
#define backlight_pin 11
U8GLIB_PCD8544 u8g(3, 4, 6, 5, 7);  // Arduino pins connected to Nokia pins:
                                    // CLK=3, DIN=4, CE=6, DC=5, RST=7
                                    
                                    
// AccelStepper Setup
AccelStepper stepper(1, A0, A1);  // 1 = Easy Driver interface
                                  // Arduino A0 connected to STEP pin of Easy Driver
                                  // Arduino A1 connected to DIR pin of Easy Driver
                                  


void setup(void) {
  
  //  Light up the LCD backlight LEDS
  analogWrite(backlight_pin, 0);  // Set the Backlight intensity (0=Bright, 255=Dim)
    
  //  AccelStepper speed and acceleration setup
  stepper.setMaxSpeed(1500);  // Not to fast or you will have missed steps
  stepper.setAcceleration(400);  //  Same here
  
  // Draw starting screen on Nokia LCD
  u8g.firstPage();
  do {
  u8g.drawHLine(0, 15, 84);
  u8g.drawVLine(50, 16, 38);
  u8g.drawHLine(0, 35, 84); 
  u8g.setFont(u8g_font_profont11);
  u8g.drawStr(0, 10, "ENTER DISTANCE");
  u8g.drawStr(62, 29, "MM");
  u8g.drawStr(4, 46, "cur-pos");
  }
  while( u8g.nextPage() );
  
}


void loop(){
  
  char keypressed = keypad.getKey();  // Get value of keypad button if pressed
  if (keypressed != NO_KEY){  // If keypad button pressed check which key it was
    switch (keypressed) {
      
      case '1':
        checknumber(1);
      break;
        
      case '2':
        checknumber(2);
      break;

      case '3':
        checknumber(3);
      break;

      case '4':
        checknumber(4);
      break;

      case '5':
        checknumber(5);
      break;

      case '6':
        checknumber(6);
      break;

      case '7':
        checknumber(7);
      break;

      case '8':
        checknumber(8);
      break;

      case '9':
        checknumber(9);
      break;

      case '0':
        checknumber(0);
      break;

      case '*':
        deletenumber();
      break;

      case '#':
        calculatedistance();
      break;
    }
  }

}

void checknumber(int x){
  if (firstnumber == 99) { // Check if this is the first number entered
    firstnumber=x;
    String displayvalue = String(firstnumber);  //  Transform int to a string for display
    drawnokiascreen(displayvalue); // Redraw Nokia lcd
    
  } else {
    if (secondnumber == 99) {  // Check if it's the second number entered
      secondnumber=x;
      String displayvalue = (String(firstnumber) + String(secondnumber));
      drawnokiascreen(displayvalue);

    } else {  // It must be the 3rd number entered
      thirdnumber=x;
      String displayvalue = (String(firstnumber) + String(secondnumber) + String(thirdnumber));
      drawnokiascreen(displayvalue);

    }
  }
}

 
void deletenumber() {  // Used to backspace entered numbers
  if (thirdnumber !=99) {
      String displayvalue = (String(firstnumber) + String(secondnumber));
      drawnokiascreen(displayvalue);

    thirdnumber=99;
  } 
  else {
    if (secondnumber !=99) {
      String displayvalue = String(firstnumber);
      drawnokiascreen(displayvalue);

      secondnumber=99;
   } 
   else {
     if (firstnumber !=99) {
       String displayvalue = "";
       drawnokiascreen(displayvalue);

       firstnumber=99;
      }
    }
  }
}
  
void calculatedistance() {  // Used to create a full number from entered numbers

    if (thirdnumber == 99 && secondnumber == 99 && firstnumber != 99) {
      keyfullnumber=firstnumber;
      movestepper(keyfullnumber);
    }
    
    if (secondnumber != 99 && thirdnumber == 99) {
      keyfullnumber=(firstnumber*10)+secondnumber;
      movestepper(keyfullnumber);
    }
    
    if (thirdnumber != 99) {
      keyfullnumber=(firstnumber*100)+(secondnumber*10)+thirdnumber;
      movestepper(keyfullnumber);
    }
    
    resetnumbers(); // Reset numbers to get ready for new entry
  } 


void movestepper(int z) {  //  Move the stepper

  int calculatedmove=((z*1600)/80);  //  Calculate number of steps needed in mm
  stepper.runToNewPosition(calculatedmove);
  currentposition = String(z);
  u8g.firstPage();
  do {
    u8g.drawHLine(0, 15, 84);
    u8g.drawVLine(50, 16, 38);
    u8g.drawHLine(0, 35, 84); 
    u8g.setFont(u8g_font_profont11);
    u8g.drawStr(0, 10, "ENTER DISTANCE");
    u8g.drawStr(62, 29, "MM");
    u8g.drawStr(4, 46, "cur-pos");
    u8g.setPrintPos(57,47);
    u8g.print(currentposition);       
  }
  while( u8g.nextPage() ); 
}
                
void resetnumbers() {  // Reset numbers for next entry
  firstnumber=99;
  secondnumber=99;
  thirdnumber=99;
} 
  

void drawnokiascreen(String y) {

    u8g.firstPage();
    do {
      u8g.drawHLine(0, 15, 84);
      u8g.drawVLine(50, 16, 38);
      u8g.drawHLine(0, 35, 84); 
      u8g.setFont(u8g_font_profont11);
      u8g.drawStr(0, 10, "ENTER DISTANCE");
      u8g.setPrintPos(0,29);
      u8g.print(y);  // Put entered number on Nokia lcd    
      u8g.drawStr(62, 29, "MM");
      u8g.drawStr(4, 46, "cur-pos");
      u8g.setPrintPos(57,47); 
      u8g.print(currentposition);  //  Display current position of stepper
    }
      while( u8g.nextPage() );

}

Make a test sketch for the display only. I suggest to use the "hd44780" library. Here is an example to start with: hd44780/HelloWorld.ino at master · duinoWitchery/hd44780 · GitHub
It is in the Library Manager with the name "hd44780". Just try a few things to get to know the library.

Then draw the layout that you want to use for the display. There are 8 character patterns that you can create to draw lines or the 'degrees' symbol.

I write my layout in the sketch:

// Layout display
//
//     01234567890123456789
//    +--------------------
//  0 |Temperature -12.3 °C
//  1 |Humidity    99%
//  2 |
//  3 |                Idle

Then make a test sketch for the keypad, another test sketch to check if you can control the stepper motors.

When that is all looking good, then you can combine them.

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