mini LCD + button tester v.02

/*
  Reddit menu example - May 8, 2019
  Displays a multi-level menu on a 20x4 LCD screen, with 5-button navigation.
  Board = Uno
  Other hardware: 20x4 I2C LCD
                  5 series-resistive buttons


  Button 1 should be left, button 2 down, button 3 up, button 4 right. 5 = select.
  buttons, resistors, pin levels:
  1   220Ω  394
  2   470Ω  329
  3   1KΩ   264
  4   2.2KΩ   194
  5   4.7KΩ   114

*/

#include "Wire.h" // For I2C (standard Arduino IDE library)
#include "LiquidCrystal_I2C.h" // Library location --- https://www.arduinolibraries.info/libraries/liquid-crystal-i2-c
LiquidCrystal_I2C lcd(0x27, 20, 4); // 0x27 is -usually- the default I2C bus address of the backpack

int buttonInput_pin = A0; // The physical input pin for buttons.
int buttonInput_pinValue = 0; // This is used for storing the actual pin value.
int button_pressed_current_value = 0;
int button_pressed_previous_value = 0;


// The variables below are used to debounce button presses.
// The buttons are going to be checked ten times a second.
// Only one button press will be detected for each time the button is pressed. Holding the button down should not result in additional 'presses' being detected.
bool buttons_enabled = true; // Used for debouncing buttons.
int button_debounce_time = 100; // A time in milliseconds to debounce the buttons.
unsigned long button_press_begin_time = 0;
unsigned long button_press_current_time = 0;



void setup() {
  Serial.begin(9600);
  lcd.init();
  // buttonInput_pin is analogRead(), doesn't require declaration
  // I2C pins A4, A5 are fixed and don't require declaration
  lcd_clear_all_lines();
  button_pressed__no_button();
  Serial.println("Exiting setup()");
}




void loop() {

  if (buttons_enabled == true) {
    check_buttons();
    start_button_timer();
  }
  else {
    check_button_timer();
  }

} // end of main loop





void check_buttons() {

  button_pressed_current_value = analogRead(buttonInput_pin);
  if (button_pressed_previous_value < 50 && button_pressed_current_value > 50) {
    lcd_print_blank_line(1);
    if (button_pressed_current_value > 50 && button_pressed_current_value < 130) {
      button_pressed__select();
    }
    if (button_pressed_current_value > 180 && button_pressed_current_value < 220) {
      button_pressed__right();
    }
    if (button_pressed_current_value > 230 && button_pressed_current_value < 290) {
      button_pressed__up();
    }
    if (button_pressed_current_value > 300 && button_pressed_current_value < 360) {
      button_pressed__down();
    }
    if (button_pressed_current_value > 370 && button_pressed_current_value < 430) {
      // left button
      button_pressed__left();
    }
  }
  button_pressed_previous_value = button_pressed_current_value;
}


void button_pressed__select() {
  lcd.setCursor(0, 0);
  lcd.print("button = select");
  Serial.println("button = select");
  delay(2000);
  button_pressed__no_button();
}

void button_pressed__right() {
  lcd.setCursor(0, 0);
  lcd.print("button = right");
  Serial.println("button = right");
  delay(2000);
  button_pressed__no_button();
}

void button_pressed__up() {
  lcd.setCursor(0, 0);
  lcd.print("button = up");
  Serial.println("button = up");
  delay(2000);
  button_pressed__no_button();
}

void button_pressed__down() {
  lcd.setCursor(0, 0);
  lcd.print("button = down");
  Serial.println("button = down");
  delay(2000);
  button_pressed__no_button();
}

void button_pressed__left() {
  lcd.setCursor(0, 0);
  lcd.print("button = left");
  Serial.println("button = left");
  delay(2000);
  button_pressed__no_button();
}

void button_pressed__no_button() {
  lcd_print_blank_line(1);
  lcd.setCursor(0, 1);
  lcd.print("button = none");
  Serial.println("button = none");
}


void start_button_timer() {
  // This is for starting the button timer. This is done every time the button input is checked.
  buttons_enabled = false;
  button_press_begin_time = millis();
}


void check_button_timer() {
  // This function re-enables the button input if button_debounce_time has passed.
  button_press_current_time = millis();
  if (button_press_current_time >= button_press_begin_time) {
    if (button_press_current_time >= (button_press_begin_time + button_debounce_time)) {
      buttons_enabled = true;
    }
  }
  else {
    button_press_begin_time = millis();
  }
}


void lcd_clear_all_lines() {
  lcd_print_blank_line(1);
  lcd_print_blank_line(2);
  lcd_print_blank_line(3);
  lcd_print_blank_line(4);
}

void lcd_print_blank_line(int lineNumber) {
  // This function 'erases' a given line by printing 20 spaces in it.
  int sLine = lineNumber - 1;
  lcd.setCursor(0, sLine);
  lcd.print("                    ");
}