The software was entirely written from scratch in Bascom. Basic language for the AVR micro controller, the Attiny2313 in this case. The code I wrote just fitted in the memory (2k), but I'm sure it could be optimised some more..

 

With the current firmware it's possible to program a certain time in minutes and seconds, start the countdown (light up the lamps), pause and stopt the countdown. You can still change the count down time, by pressing 'pause', then increase the counter, and press 'play' again. During 'pause' the lamps will go out.

 

The start / stop buttons and the min / sec up and down buttons are all connnected to their own pins on the AVR and to the interrupt pins. When a button is pressed, an interrupt is generated and the AVR reads the input pins to see which button was pressed.

 

During count down, only  the start / stop buttons can generate interrupts, in pause or stop mode, all buttons can generate interrupts. The LCD is connected in 4 bit mode and the standard Bascom LCD library is used to display text on the LCD.

 

The LCD will show the current status (running, paused, stopped) and the current time (minutes and seconds).