This project was a rapid work. The firmware based on the Usb4All, so I did not need write it from the begining.
The firmware has an accuracy compensator, so the prototype board has a delay of less than 2 seconds in half a year. And there is also a DS18B20 interface on the board for measuring the temperature.
I got these 7 segment displays from an old stock, so I have limited amount only from them. I made two types board, one of them use pre-biased transistors for control the common anodes of the displays, another one use dual packeged mos-fet transistors
I put an eastern egg into the firmware. If you see the third image, you can recognize an inpossible minute and second value, but the truth is that both clock shows same time, because the upper shows it in number system 8
To set the clock, it possible from the uart port only at the moment. If youi'd like to show the firmware sources you can see it here.