module pmodenc(
clk,
rst_n,
A,
B,
BTN,
// A_Debounce,
// B_Debounce,
// BTN_Debounce,
// Rotary_right,
// Rotary_left
LED
);

input wire clk,rst_n;
input wire A,B,BTN;
// output wire A_Debounce,B_Debounce,BTN_Debounce;
// output wire Rotary_right,Rotary_left;
output wire [5:0]LED;

reg clk_10ms;
reg [31:0]count;

reg A_reg,A_reg0;
reg B_reg,B_reg0;
reg BTN_reg,BTN_reg0;
wire A_Debounce;
wire B_Debounce;
wire BTN_Debounce;

reg A_Debounce_reg;
reg B_Debounce_reg;
wire A_pos,A_neg;
wire B_pos,B_neg;

reg rotary_right;
reg rotary_left;

reg rotary_right_reg,rotary_left_reg;
wire rotary_right_pos,rotary_left_pos;
wire rotary_event;

reg [5:0]shift_d;

always@(posedge clk,negedge rst_n)begin
if(!rst_n)begin
count <= 0;
clk_10ms <= 1'b0;
end
else begin
if(count < 32'd24_999)begin//10ms消抖，25MCLK
count <= count + 1'b1;
clk_10ms <= 1'b0;
end
else begin
count <= 0;
clk_10ms <= 1'b1;
end
end
end

always@(posedge clk,negedge rst_n)begin
if(!rst_n)begin
A_reg <= 1'b1;
A_reg0 <= 1'b1;
B_reg <= 1'b1;
B_reg0 <= 1'b1;
BTN_reg <= 1'b0;
BTN_reg0 <= 1'b0;
end
else begin
if(clk_10ms)begin
A_reg <= A;
A_reg0 <= A_reg;
B_reg <= B;
B_reg0 <= B_reg;
BTN_reg <= BTN;
BTN_reg0 <= BTN_reg;
end
end
end

assign A_Debounce = A_reg0 && A_reg && A;
assign B_Debounce = B_reg0 && B_reg && B;
assign BTN_Debounce = BTN_reg0 && BTN_reg && BTN;//消抖后制作脉冲上升沿

always@(posedge clk,negedge rst_n)begin
if(!rst_n)begin
A_Debounce_reg <= 1'b1;
// B_Debounce_reg <= 1'b1;
end
else begin
A_Debounce_reg <= A_Debounce;
// B_Debounce_reg <= B_Debounce;
end
end

assign A_pos = !A_Debounce_reg && A_Debounce;
// assign B_pos = !B_Debounce_reg && B_Debounce;

assign A_neg = A_Debounce_reg && !A_Debounce;
// assign B_neg = B_Debounce_reg && !B_Debounce;

always@(posedge clk,negedge rst_n)begin
if(!rst_n)begin
rotary_right <= 1'b1;
rotary_left <= 1'b1;
end
else begin
if(A_pos && !B_Debounce)begin//A的上升沿时候如果B为低电平，则旋转编码器是向右转
rotary_right <= 1'b1;
end

if(A_pos && B_Debounce)begin//A上升沿时候如果B为低电平，则旋转编码器是向左转
rotary_left <= 1'b1;
end

if(A_neg && B_Debounce)begin//A的下降沿B为高电平，则向右转结束
rotary_right <= 1'b0;
end

if(A_neg && !B_Debounce)begin//A的下降沿B为低电平，则向左转结束
rotary_left <= 1'b0;
end
end
end

// assign Rotary_left = rotary_left;
// assign Rotary_right = rotary_right;
always@(posedge clk,negedge rst_n)begin
if(!rst_n)begin
rotary_right_reg <= 1'b1;
rotary_left_reg <= 1'b1;
end
else begin
rotary_right_reg <= rotary_right;
rotary_left_reg <= rotary_left;
end
end

assign rotary_right_pos = !rotary_right_reg && rotary_right;
assign rotary_left_pos = !rotary_left_reg && rotary_left;//消抖

assign rotary_event = rotary_right_pos || rotary_left_pos;//转动标志位

always@(posedge clk,negedge rst_n)begin
if(!rst_n)
shift_d <= 6'b111_110;
else if(rotary_event)begin
if(rotary_right_pos)
shift_d <= {shift_d[0],shift_d[5:1]};
if(rotary_left_pos)
shift_d <= {shift_d[4:0],shift_d[5]};
end
end

assign LED = shift_d;//灯的向左向右的测试模块

endmodule

原理的话可以参考下这位大神讲的http://www.eeboard.com/bbs/forum.php?mod=viewthread&tid=45184&highlight=%E5%B0%8F%E8%84%9A%E4%B8%AB