I want to make a countdown timer.I have no idea to program it.Can any one help me? The time number display on the 1602 LCD,and there have 4 button.The first button is begin countdown of time.The second is exchange the unit of time( hour minute second).The third button is add the number,such as if you press the second button there are have a logo display on the hour or minute or second one of them,if the loge in the minute position the minute number add 1 when you press the first button.The fourth button is subtraction the function that is the same thing as the third button.
One here but you will need to read all of the instructions.