#include <Wire.h>
#include <LiquidCrystal_I2C.h>

LiquidCrystal_I2C lcd(0x27, 16, 2);

#define BUTTON_PIN D2
#define POT_PIN A0

bool powerState = false;
bool lastButton = HIGH;

void setup() {
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  lcd.init();
  lcd.clear();
}

void loop() {

  bool btn = digitalRead(BUTTON_PIN);

  // переключение состояния
  if (btn == LOW && lastButton == HIGH) {
    powerState = !powerState;
    delay(200);
  }

  lastButton = btn;

  if (!powerState) {
    lcd.noBacklight();
    lcd.clear();
    return;
  }

  lcd.backlight();

  int pot = analogRead(POT_PIN);

  String mode;

  if (pot < 340) mode = "Golova";
  else if (pot < 680) mode = "Grud'";
  else mode = "Spina";

  lcd.setCursor(0, 0);
  lcd.print("Rezhim:");

  lcd.setCursor(0, 1);
  lcd.print("                ");
  lcd.setCursor(0, 1);
  lcd.print(mode);

  delay(100);
}