StopWatch

I want to thank PCBWAY to sponsor this project. Without them, this would have been impossible.

https://www.pcbway.com/

Components are placed, trying to use the fewer space possible in a 4-layer PCB. https://www.pcbway.com/ was the sponsor of the project:

and finally:

Before designing the PCB, I simulated the complete project so I really know that everything will work like a charm:

This also has helped me to achieve the code even before having a PCB

The design is simple: The pic18LF14k50 drives some NPN transistors, which allow the display to light. Same for the buzzer&LED indicator. In this case, we also use a boolean inverter (74LVC1G06GW,125 from Nexperia) so only one of the two displays is on at every moment. we did that because we are using 100% of the pins in the PIC.

As you may know, the display has two pairs of four displays in parallel (A total of eight displays!), so we will need to have a high-frequency blink in order to "trick" the human eye to see them all light at the same time. 

For the buttons, an RC filter made of a 10K resistor and 100nF will filter any bouncing effect, having a great counting experience. An additional diode here avoids messing with the programming signals.