ESP32 - pH sensor

esp32.ino

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

LiquidCrystal_I2C lcd(0x27, 16, 2);

float calibration_value = 21.34 + 1.5;
unsigned long int avgval;
int buffer_arr[10], temp;
float ph_act;

#define PH_SENSOR_PIN 34   

void setup() {
  Wire.begin();
  Serial.begin(115200);  
  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("pH Sensor Ready");
  delay(2000);
  lcd.clear();
}

void loop() {
  for (int i = 0; i < 10; i++) {
    buffer_arr[i] = analogRead(PH_SENSOR_PIN);
    delay(30);
  }

  for (int i = 0; i < 9; i++) {
    for (int j = i + 1; j < 10; j++) {
      if (buffer_arr[i] > buffer_arr[j]) {
        temp = buffer_arr[i];
        buffer_arr[i] = buffer_arr[j];
        buffer_arr[j] = temp;
      }
    }
  }

  avgval = 0;
  for (int i = 2; i < 8; i++)
    avgval += buffer_arr[i];

  float volt = (float)avgval * 3.3 / 4095.0 / 6;
  ph_act = -5.70 * volt + calibration_value;

  Serial.print("pH Value: ");
  Serial.println(ph_act);

  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("pH Value:");
  lcd.setCursor(0, 1);
  lcd.print(ph_act, 2);    

  delay(1000); 
}