Rotary Encoder LCD Menu

// Rotary Encoder LCD Menu - turn the knob to scroll a menu on a classic
// 16x2 character LCD, push the shaft to run the highlighted action.
// The ESP32Encoder library counts KY-040 quadrature pulses with the
// ESP32's hardware pulse counter (PCNT), so no polling races:
// encoder.getCount() always has the truth, 2 counts per detent here.
// In the Lab, hover the encoder knob and scroll to rotate it; click to press.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>
#include <ESP32Encoder.h>

#define CLK_PIN 26
#define DT_PIN  27
#define SW_PIN  14   // encoder push switch, active LOW
#define LED_PIN 4
#define ITEMS   5

LiquidCrystal_I2C lcd(0x27, 16, 2);
ESP32Encoder encoder;

int sel = 0;
long lastCount = 0;
bool inItem = false;
bool swWas = true;
unsigned long lastPress = 0;
const char* itemName = "LED ON";

void updateName(int n) {
  itemName = "ABOUT";
  if (n == 0) itemName = "LED ON";
  else if (n == 1) itemName = "LED OFF";
  else if (n == 2) itemName = "BLINK 3X";
  else if (n == 3) itemName = "COUNT";
}

void drawMenu() {
  updateName(sel);
  lcd.clear();
  lcd.print(">");
  lcd.print(itemName);
  lcd.setCursor(13, 0);
  lcd.print(sel + 1);
  lcd.print("/5");
  lcd.setCursor(0, 1);
  lcd.print("turn+push knob");
}

void runItem() {
  lcd.clear();
  lcd.setCursor(0, 0);
  if (sel == 0) {
    digitalWrite(LED_PIN, HIGH);
    lcd.print("LED is ON");
    Serial.println("ACTION: LED ON");
  } else if (sel == 1) {
    digitalWrite(LED_PIN, LOW);
    lcd.print("LED is OFF");
    Serial.println("ACTION: LED OFF");
  } else if (sel == 2) {
    lcd.print("Blinking...");
    Serial.println("ACTION: BLINK 3X");
    for (int k = 0; k < 3; k++) {
      digitalWrite(LED_PIN, HIGH);
      delay(120);
      digitalWrite(LED_PIN, LOW);
      delay(120);
    }
  } else if (sel == 3) {
    lcd.print("Count ");
    lcd.print(encoder.getCount());
    Serial.print("ACTION: COUNT ");
    Serial.println(encoder.getCount());
  } else {
    lcd.print("FluxBench demo");
    Serial.println("ACTION: ABOUT");
  }
  lcd.setCursor(0, 1);
  lcd.print("push = back");
}

void setup() {
  Serial.begin(115200);
  pinMode(SW_PIN, INPUT_PULLUP);
  pinMode(LED_PIN, OUTPUT);
  ESP32Encoder::useInternalWeakPullResistors = puType::up;
  encoder.attachHalfQuad(DT_PIN, CLK_PIN);  // 2 counts per detent
  encoder.setCount(0);
  lcd.init();
  lcd.backlight();
  Serial.println("Rotary menu ready - turn to scroll, push to select");
  drawMenu();
}

void loop() {
  long c = encoder.getCount();
  long diff = c - lastCount;
  if (!inItem && diff >= 2) {          // one detent clockwise
    sel = (sel + 1) % ITEMS;
    lastCount = lastCount + 2;
    updateName(sel);
    Serial.print("MENU: ");
    Serial.println(itemName);
    drawMenu();
  } else if (!inItem && diff <= -2) {  // one detent counter-clockwise
    sel = (sel + ITEMS - 1) % ITEMS;
    lastCount = lastCount - 2;
    updateName(sel);
    Serial.print("MENU: ");
    Serial.println(itemName);
    drawMenu();
  } else if (inItem) {
    lastCount = c;                     // ignore turns inside an item screen
  }

  bool sw = digitalRead(SW_PIN);
  if (swWas && !sw && millis() - lastPress > 200) {
    lastPress = millis();
    if (inItem) {
      inItem = false;
      Serial.println("BACK to menu");
      drawMenu();
    } else {
      inItem = true;
      runItem();
    }
  }
  swWas = sw;
  delay(5);
}