#include <LiquidCrystal_I2C.h>
#define trigPin 5
#define echoPin 4
#define ledRed 8
#define ledYellow 7
#define ledGreen 6
#define sensorPos 400 //posisi ketinggian sensor dari dasar sungai

LiquidCrystal_I2C lcd(0x27,20,4);

float readDist() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  int duration = pulseIn(echoPin,HIGH);
  return duration * 0.034 / 2;
}

void allOff(){
  digitalWrite(ledRed, LOW);
  digitalWrite(ledYellow, LOW);
  digitalWrite(ledGreen, LOW);
}

void setup() {
  lcd.init();                     
  lcd.backlight();
  lcd.setCursor(1,0);
  lcd.print("Ketinggian Air");
  lcd.setCursor(9,1);
  lcd.print("cm");
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(ledRed, OUTPUT);
  pinMode(ledYellow, OUTPUT);
  pinMode(ledGreen, OUTPUT);
}

void loop() {
  float distance = readDist();
  float level = sensorPos - distance;
  lcd.setCursor(1,1);
  lcd.print(level);

  if(level<101) {
    allOff();
    digitalWrite(ledRed, HIGH);
  }else if(level<151) {
    allOff();
    digitalWrite(ledYellow, HIGH);
  } else {
    allOff();
    digitalWrite(ledGreen,HIGH);
  }
}