Two Atmega328p used to implement clock with temperature and humidity sensor using HUB75 16x32 RGB LED Matrix as display.
DS1307 RTC with battery backup used for time keeping.
Originally I planned to use HTU21D as temperature and humidity sensor. But I think I will replace it with SHT21 5V module.
I still need to create enclosure.
(It is four buttons that are not connected in the picture.)
Eagle schematic and PCB design attached. Also attached sketches for both MCUs. The clock currently fully functional, but I am going to make improvements.