module PS2Receiver(
    input clk,
    input kclk,
    input kdata,
    output reg [15:0] keycodeout,
    output keycode_valid
    );

    reg flag;
    reg [3:0] flag_shift;
    wire kclkf, kdataf;
    reg [3:0]cnt;

    assign keycode_valid = flag_shift[0] && !flag_shift[2];

    initial begin //for tb
      cnt = 0;
      keycodeout = 0;
      flag_shift = 0;
      flag = 0;
    end

debouncer debounce(
    .clk(clk),
    .I0(kclk),
    .I1(kdata),
    .O0(kclkf),
    .O1(kdataf)
);
always@(posedge clk) begin
    flag_shift <= (flag_shift << 1) + flag;
end

always@(negedge(kclkf))begin
    case(cnt)
    0:if(keycodeout != 16'hE000)keycodeout <= 0;//Start bit
    1:keycodeout[0]<=kdataf;
    2:keycodeout[1]<=kdataf;
    3:keycodeout[2]<=kdataf;
    4:keycodeout[3]<=kdataf;
    5:keycodeout[4]<=kdataf;
    6:keycodeout[5]<=kdataf;
    7:keycodeout[6]<=kdataf;
    8:keycodeout[7]<=kdataf;
    //TODO ADD PARITY CHECK
    9:begin
        flag<=1'b1;
        if(keycodeout[7:0] == 8'hE0) begin
            keycodeout <= {keycodeout[7:0], 8'd0};
        end
    end
    10:flag<=1'b0;
    default: cnt <= 0;
    endcase
        if(cnt<=9) cnt<=cnt+1;
        else if(cnt==10) cnt<=0;
end

endmodule


module debouncer(
    input clk,
    input I0,
    input I1,
    output reg O0,
    output reg O1
    );
    
    reg [4:0]cnt0, cnt1;
    reg Iv0=0,Iv1=0;
    reg out0, out1;
    
always@(posedge(clk))begin
    if (I0==Iv0)begin
        if (cnt0==19)O0<=I0;
        else cnt0<=cnt0+1;
      end
    else begin
        cnt0<="00000";
        Iv0<=I0;
    end
    if (I1==Iv1)begin
            if (cnt1==19)O1<=I1;
            else cnt1<=cnt1+1;
          end
        else begin
            cnt1<="00000";
            Iv1<=I1;
        end
    end
    
endmodule