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module key_scan
#(
parameter KEY_WIDTH = 2
)
(
input clk, //50MHz
input rst_n,
input [KEY_WIDTH-1:0] key_data,
output key_flag,
output reg [KEY_WIDTH-1:0] key_value
);
//---------------------------------
//escape the jitters
reg [19:0] key_cnt; //scan counter
reg [KEY_WIDTH-1:0] key_data_r;
always @(posedge clk or negedge rst_n)
begin
if(!rst_n)
begin
key_data_r = {KEY_WIDTH{1'b1}};
key_cnt = 0;
end
else
begin
key_data_r = key_data; //lock the key value
if((key_data == key_data_r) (key_data != {KEY_WIDTH{1'b1}})) //20ms escape jitter
begin
if(key_cnt 20'hfffff)
key_cnt = key_cnt + 1'b1;
end
else key_cnt = 0;
end
end
wire cnt_flag = (key_cnt == 20'hffffe) ? 1'b1 : 1'b0;//!!
//-----------------------------------
//sure the key is pressed
reg key_flag_r;
always@(posedge clk or negedge rst_n)
begin
if(!rst_n)
begin
key_flag_r = 0;
key_value = 0;
end
else if(cnt_flag)
begin
key_flag_r = 1;
key_value = key_data; //locked the data
end
else //let go your hand
key_flag_r = 0; //lock the key_value
end
//---------------------------------------
//Capture the rising endge of the key_flag
reg key_flag_r0,key_flag_r1;
always@(posedge clk or negedge rst_n)
begin
if(!rst_n)
begin
key_flag_r0 = 0;
key_flag_r1 = 0;
end
else
begin
key_flag_r0 = key_flag_r;
key_flag_r1 = key_flag_r0;
end
end
assign key_flag = ~key_flag_r1 key_flag_r0;
endmodule
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