Recommended time length of press debouncing/release debouncing with buttons of Basys3 FPGA

Question

I am doing an algorithmic state machine in VHDL. It models a slot machine. It uses debouncing for the start and end input signals. I need to implement it later on a Basys 3 FPGA. The start and end input signals are modeled with the FPGA buttons. The frequency of the CLK signal of the Basys3 FPGA is 100 MHz. Therefore the period of CLK must be 10^-8 seconds= 10*10^-9 seconds = 10 ns.

• What time length do you recommend for the press debouncing time when pressing the buttons of the Basys3?
• What time length do you recommend for the release debouncing time when releasing the buttons of the Basys3?

Answer 1

There are two buttons. One of them for starting the slot machine and another one to stop it.

So, if the start button activates immediately and then bounces for several ms who cares - it's not until the stop button is pressed that you need to take any subsequent action and, that can happen immediately as well. Of course, if some fool is pressing both (and that's a problem) then you need to do some thinking about the situation but, I don't see that de-bouncing will help you in that scenario either.

De-bouncing is only really necessary in applications like telephone keypads where multiple false presses will cause a number to be mis-dialled.