Module: Debouncer

Problem Statement

When a button is pressed, mechanical contacts may cause the signal to "bounce" (i.e., generate multiple transitions or glitches) before settling into a stable state. The task is to implement a debouncing circuit that filters out these glitches and provides a clean signal indicating a valid button press.

Module Name: debouncer

Parameters

Parameter	Comment
CLK_FREQ_MHZ	Frequency of the clk_i signal in MHz.
GLITCH_TIME_NS	Maximum expected duration for which bounce (glitches) can be observed, in nanoseconds.

Signal Descriptions

Signal Name	Direction	Width	Comment
clk_i	input	1	Clock signal.
key_i	input	1	Button signal (0 - pressed, 1 - not pressed).
key_pressed_stb_o	output	1	Strobe (pulse) for one clock cycle, indicating a valid button press.

Explanation of the Code

1. Debouncing Logic:

   • The button input key_i is synchronized using two flip-flops (key1 and key2) to mitigate metastability issues that arise due to asynchronous input signals.
   • The signal key2 represents the debounced signal, which is delayed by two clock cycles.

2. Glitch Filtering:

   • The GLITCH_CLKS parameter is calculated by multiplying the glitch time (GLITCH_TIME_NS) in nanoseconds by the clock frequency (CLK_FREQ_MHZ) in MHz, and dividing by 1000 to convert nanoseconds into clock cycles.
   • The counter cnt increments each clock cycle when the button is pressed (~key2). If the button is released or the strobe signal (key_pressed_stb_o) is asserted, the counter resets to zero.