// LCD1602 to Arduino Uno connection example


#include <LiquidCrystal.h>



// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 10, 9, 8, 7);

//pin numbers
const int trigger=5,echo=6;


//variables:
float distance,duration;
int percent,prevPercent=0;
unsigned long startTime,currentTime=0;

//parameters:
//fullThreshold is percentage at which bin should be emptied
//delayTime is the delay between each loop in milliseconds
//maxDuration is the maximum time the bin can be left without being emptied
//binHeight is the height of the bin
//emptyThreshold is thepercent at which bin is considered empty 
const int fullThreshold=75,delayTime=100,maxDuration=3000,binHeight=300,emptyThreshold=5;

void setup() {
  Serial.begin(9600);
  pinMode(trigger,OUTPUT);
  pinMode(echo,INPUT);
  
  // set up the LCD's number of columns and rows:
  lcd.begin(16, 2);
  // start timer to empty bin even if it doesn't exceed fullThreshold
  startTime=millis();
  Serial.begin(115200);
  
  
  delay(10);
  Serial.println();
 
}

void loop() {
  digitalWrite(trigger,LOW);
  delayMicroseconds(5);        
  digitalWrite(trigger,HIGH);  
  delayMicroseconds(10);      
  digitalWrite(trigger,LOW); 
  duration=pulseIn(echo,HIGH);
  //distance in cm = (speed in cm/s) * (duration in seconds divided by 2 for the back and forth trip)
  distance = 34300 * (duration*0.000001/2);
  percent = ((binHeight-distance)/binHeight)*100;

  //for debugging purposes, distance can be displayed on serial monitor
  /*
  Serial.println (percent);
  Serial.print ("Distance = ");
  Serial.print (distance);         
  Serial.println (" cm"); 
  */      
    
  
  if (percent>100 || percent<0) {
    lcd.setCursor(0, 0);
    lcd.print("!!!ERROR!!!                  ");
    lcd.setCursor(0, 1);
    lcd.print("                        ");
    
    startTime=millis();
  }
  else if (percent>fullThreshold){
    empty();
    startTime=millis();
  }else{
  	currentTime=millis();
    if (currentTime - startTime > maxDuration){
      empty();
    }else{
    display();
    }
  }
  
  if(prevPercent>emptyThreshold && percent<=emptyThreshold){
    startTime=millis();
  }
  
  prevPercent=percent;
  delay(delayTime);
  
  
}
      
void empty(){
    lcd.setCursor(0, 0);
    lcd.print(percent);
    lcd.print("% FULL!!!              ");
    lcd.setCursor(0, 1);
    lcd.print("Please empty.");
    
}

void display(){
    lcd.setCursor(0, 0);
    lcd.print(percent);
    lcd.print("% full              ");
    lcd.setCursor(0, 1);
    lcd.print("                        ");
    
}