/*
    Visualizzare su un display la distanza rilevata tramite un sensore di prossimità, 
    facendo lampeggiare un led se questa diminuisce sotto i 10cm.
*/

#include <LiquidCrystal_I2C.h> //libreria per il display
#define ALLARMLIMIT 10 // distanza mimina sotto cui scatta l'alert
#define LEDPIN 8
#define TRIGGERPIN 3
#define ECHOPIN 2

LiquidCrystal_I2C lcd(0x27,20,4);

float distance = 0;
bool alarmOn = false;

long readUltrasonicDistance()
{
	digitalWrite(TRIGGERPIN, LOW);
	delayMicroseconds(2);
	digitalWrite(TRIGGERPIN, HIGH);
	delayMicroseconds(10);
	digitalWrite(TRIGGERPIN, LOW);

	return pulseIn(ECHOPIN, HIGH) / 58;
}

void checkDistance(){
    if(distance < ALLARMLIMIT && !alarmOn){
        digitalWrite(LEDPIN, HIGH);
        alarmOn = !alarmOn;
    }else if(distance >= ALLARMLIMIT && alarmOn){
        digitalWrite(LEDPIN, LOW);
        alarmOn = !alarmOn;
    }
}

void setup()
{
    Serial.begin(9600);
    pinMode(TRIGGERPIN, OUTPUT);
    pinMode(ECHOPIN, INPUT);
    pinMode(LEDPIN, OUTPUT);
    lcd.init();
    lcd.backlight();
    lcd.print("--> Distance <--");
	delay(2000);
	lcd.clear();
}

void loop()
{
    if(readUltrasonicDistance() != distance){
        distance = readUltrasonicDistance();
        checkDistance();
        lcd.clear();
        lcd.setCursor(0,0);
        lcd.print("Distance");
        lcd.setCursor(0,1);
        lcd.print("cm:");
        lcd.setCursor(11,1);
        lcd.print(distance, 1);
    }
	delay(500);
}