A program for clock using IN-18 indicators.
Unlike many schemes, this uses a static display. The Atmega microcontroller controls the indicators via the 74hc595 IC connected to the SPI. In addition to the IN-18, the clock has eight lights to show the day of the week and an alarm clock, and four lights to separate digits.
The microcontroller clocks from quartz at a frequency of 16 MHz. This is caused by the presence of software PWM to adjust the brightness of the indicators. The PWM frequency is selected at about 100 Hz to reduce the visibility of flicker. The same mechanism of the program PWM allows you to make the effect of a smooth change of indication indications.
A slightly modified Chan player is used as an alarm signal.