- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Hi you
I wrote a simple code for a debouncer circuit, and I appreciate if you can have a look and correct what's wrong.
module debouncer (noisy,clk_1KHz,debounced);
input wire clk_1KHz, noisy;
output wire debounced;
reg cnt;
//counter: waits that button is pressed at least 10ms
always @ (posedge clk_1KHz)
begin
if (noisy) cnt <= cnt + 1'b1;
else cnt <= 0;
end
assign debounced = (cnt==4'b1010) ? 1'b1 : 1'b0;
endmodule
what you think about it?:confused: thank you all GP
Link Copied
6 Replies
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
module debouncer (noisy,clk_1KHz,debounced);
input wire clk_1KHz, noisy;
output reg debounced;
reg reg;
//reg: wait for stable
always @ (posedge clk_1KHz)
begin
reg <= {reg,noisy}; //shift register
if(reg == 8'b00000000)
debounced <= 1'b0;
else if(reg == 8'b11111111)
debounced <= 1'b1;
else debounced <= debounced;
end
endmodule
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Thank you for your fast reply!:)
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
dear ARTEM_BOND,
I read your post, and I found their brilliant solution! I'm trying to build a simple and efficient verilog code, to solve the problem of noise... I made the following modification in your code, hoping to get a greater number of shifts:
module debouncer (noisy, clock, debounced);
input wire clock, noisy;
output reg debounced;
parameter M = 8;
reg reg;
//reg: wait for stable
always @ (posedge clock)
begin
reg <= {reg,noisy}; // N shift register
if(reg == (2**M)*0)
debounced <= 1'b0;
else if(reg == (2**M)-1)
debounced <= 1'b1;
else debounced <= debounced;
end
endmodule
I think something is wrong in the code because I can notice any noise, by oscilloscope, even increased the value of M. Could you help me with this?
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
Couple of suggestions:
(1) Instead of doing:(reg == (2**M)*0)
you could do: (~|reg)
And similarly for: (reg == (2**M)-1)
do: (®)
Personally I think it looks cleaner. (2) It is really not a good idea to call a register 'reg'. 'reg' is a reserved keyword and should be used as the name. Perhaps a better name would be: reg shift;
Or something similar.
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
dear TCWORLD,
I would like to clarify that this code is written by the Altera Teacher ARTEM_BOND and "reg" is authored by himself. I left exactly as he wrote, to not cause confusion. Below is my code which coincidentally, was exactly the name I used:
module debounce(
input wire clock,
input wire IN,
output reg OUT
);
parameter M = 8;
reg shift;
//shift: wait for stable
always @ (posedge clock)
begin
shift <= {shift,IN}; // N shift register
// if(shift == (2**M)*0)
if(~|shift)
OUT <= 1'b0;
// else if(shift == (2**M)-1)
else if(&shift)
OUT <= 1'b1;
else OUT <= OUT;
end
endmodule
If I understand correctly what you suggested, their changes are only to make the code cleaner... It really was it, nothing worked to help me, because nothing was fixed!!! As I requested earlier: ..."I think something is wrong in the code because I can notice any noise, by oscilloscope, even increased the value of M. Could you help me with this?" (Excuse me if not expressed myself correctly, my English is not very good.)
- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Report Inappropriate Content
For someone who found this topic looking for a working debouncer.
The correct code:
module debounce(
input wire clock,
input wire IN,
output reg OUT
);
parameter M = 8;
reg [M:0]shift;
//shift: wait for stable
always @ (posedge clock)
begin
shift <= {shift,IN}; // N shift register
if(~|shift)
OUT <= 1'b0;
else if(&shift)
OUT <= 1'b1;
else OUT <= OUT;
end
endmodule

Reply
Topic Options
- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Printer Friendly Page