https://purengom.com/2010/09/26/%eb%a7%a5%eb%b6%81-%ed%94%84%eb%a1%9c-lcd%ec%99%b8%ec%9e%a5-%ed%81%b4%eb%a6%ac%eb%8b%9d%ec%9d%98-%eb%b9%84%ea%b8%b0/