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

LiquidCrystal_I2C lcd(0x27,16,2);  // set the LCD address to 0x27 for a 16 chars and 2 line display

// Anschlüsse:
// GND - GND
// VCC - 5V
// SDA - ANALOG Pin 4
// SCL - ANALOG pin 5

#include <HX711.h>                       

HX711 scale(A2, A1);  


long sensorValue;     // Einlesewert vom Potentiometer
long Rohwert;         // vom HX711 gelieferter Rohwert

int h;                // Fallhöhe

float g;

long time_start, time_end;

const int buttonPin = 8;     // the number of the pushbutton pin
int triggerPin = 2;          // the number of the trigger pin for the solenoid
int sensorPin = A0;          // pin for reading the potentiometer


// =====================
// ======= SETUP =======
// =====================

void setup()
   { 
    Serial.begin(115200); 
    
    scale.set_gain(128);   // A-Kanal: gain = 64 oder 128; B-Kanal: fix 32
    
    pinMode(buttonPin, INPUT);
    pinMode(triggerPin, OUTPUT);

    digitalWrite(triggerPin, LOW);

    Rohwert = scale.read();
    
    lcd.begin();                      // initialize the lcd

    // Print a message to the LCD.
    lcd.backlight();
    lcd.setCursor(0,0);
    lcd.print("Erd-");
    lcd.setCursor(0,1);
    lcd.print("beschleunigung");
    
    delay(3000);

    lcd.setCursor(0,0);
    lcd.print("      ");
    lcd.setCursor(0,1);
    lcd.print("               ");    
   }


// ============================
// ======= HAUPTSCHLEIFE ======
// ============================

void loop()
   {
    lcd.setCursor(0,0);
    lcd.print("Eingabe Hoehe:");
    lcd.setCursor(0,1);
    lcd.print("h = ");
    lcd.setCursor(8,1);
    lcd.print("mm");
        
    while(digitalRead(buttonPin) == LOW)
       {
        sensorValue = analogRead(sensorPin);
    
        sensorValue = map(sensorValue,0,1023,0,9);

        lcd.setCursor(6,1);
        lcd.print(sensorValue);        
       }
    
    delay(300);
    
    h = sensorValue * 1;

    while(digitalRead(buttonPin) == LOW)
       {
        sensorValue = analogRead(sensorPin);
    
        sensorValue = map(sensorValue,0,1023,0,9);

        lcd.setCursor(5,1);
        lcd.print(sensorValue);        
       }

    delay(300);
    
    h = h + sensorValue * 10;

    while(digitalRead(buttonPin) == LOW)
       {
        sensorValue = analogRead(sensorPin);
    
        sensorValue = map(sensorValue,0,1023,0,9);

        lcd.setCursor(4,1);
        lcd.print(sensorValue);        
       }

    delay(300);
    
    h = h + sensorValue * 100;

    Serial.print("h = ");
    Serial.print(h);
    Serial.println(" mm");

    lcd.setCursor(0,0);
    lcd.print("h = ");
    lcd.print(h);
    lcd.print(" mm       ");
    lcd.setCursor(0,1);
    lcd.print("press button    ");
   
    while(digitalRead(buttonPin) == LOW)
       {
       }

    delay(300);

    // Start the experiment
    // ====================

    digitalWrite(triggerPin, HIGH);
    
    lcd.setCursor(0,0);
    lcd.print("ball in position ");
    lcd.setCursor(0,1);
    lcd.print("press button     ");

    while(digitalRead(buttonPin) == LOW)
       {
       }
    
    delay(1000);

    digitalWrite(triggerPin, LOW);
    
    time_start = millis();

    while(scale.read() > 1.05 * Rohwert)    // wait for the ball colliding with the scale
       {
        
       }
        
    time_end = millis();
    
    g = 2 * h * 1000.0 /((time_end - time_start) * (time_end - time_start));
    
    lcd.setCursor(0,0);
    lcd.print("g = ");
    lcd.print(g);
    lcd.print(" m/s2       ");
    lcd.setCursor(0,1);
    lcd.print("press button       ");
    
    while(digitalRead(buttonPin) == LOW)
       {           
       }

    delay(300);

    lcd.setCursor(0,0);
    lcd.print("                ");
    lcd.print(g);
    lcd.setCursor(0,1);
    lcd.print("                ");
        
   }