A (very) simple clock with alarm written in C for training purposes.
The code is written for the purpose of acquaintance with timers, interrupts, buttons. Seconds are counted in the interrupt timer. The time setting is done using two buttons. The alarm is set using the external interrupt buttons. The display is on the shift register. As a siren there is a light-emitting diode. When the alarm goes on, the LED blinks. Part of code written by @thodnev. Thanks for helping Timofei Hodnev.
More information you can get here