#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27,16,2); // 若LCD 無法啟用，請將0X3F 改為0X27
int x ;
unsigned long dt;
void setup() {
Serial.begin(9600);
lcd.init();
lcd.backlight();
lcd.clear();
pinMode(13,OUTPUT);
}
void loop() {
digitalWrite(13,0);
do{
x = analogRead(A0) ;
lcd.setCursor(0,1);
lcd.print("Ready...");
}while(x>5);
int y= random(2,9);
delay(y*1000);
digitalWrite(13,1);
long t1 = millis();
do{
x = analogRead(A0);
}while(x<500);
long t2 = millis();
dt = t2-t1 ;
lcd.clear();
lcd.setCursor(0,0);
lcd.print(dt);
}