---

前言

环境：
1、Quartus18.0
2、vscode
3、板子型号：EP4CE6F17C8
要求：
按键1按下，流水灯从右开始向左开始流动，按键2按下，流水灯从左开始向右开始流动，按键3按下LED每隔1s进行亮灭，按键4按下LED常亮。

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一、按键

“自锁”是指开关能通过锁定机构保持某种状态（通或断），“轻触”是说明操作开关使用的力量大小。cyclone IV开发板上的按键属于轻触式按键。

二、系统设计

1、模块框图

2、RTL视图

三、源码

module key_led #(parameter  MAX_NUM = 24'd9_999_999)(
    input   clk,
    input   rst_n,
    input   [3:0] key,

    output  reg [3:0] led
);

//parameter  MAX_NUM = 24'd9_999_999;//0.2s
reg [1:0] state;
reg [23:0] cnt;
reg [3:0]  key_r;

always @(posedge clk or negedge rst_n) begin
    if(!rst_n)begin
        cnt <= 24'd0;
    end
    else if (cnt == MAX_NUM) begin
        cnt <= 24'd0;
    end
    else begin
        cnt <= cnt + 1'd1;
    end
end

always @(posedge clk or negedge rst_n) begin
    if(!rst_n)begin
        state <= 24'd0;
    end
    else if (cnt == MAX_NUM) begin
        state <= state + 2'd1;
    end
    else begin
        state <= state;
    end
end

always @(posedge clk or negedge rst_n) begin
    if(!rst_n)begin
        led <= 4'b0000;
    end
    else if (key[0] == 0) begin
            case (state)
                2'd0 : led <= 4'b0001;
                2'd1 : led <= 4'b0010;
                2'd2 : led <= 4'b0100;
                2'd3 : led <= 4'b1000; 
                default: ;
            endcase
        end
    else if (key[1] == 0) begin
            case (state)
                2'd0 : led <= 4'b1000;
                2'd1 : led <= 4'b0100;
                2'd2 : led <= 4'b0010;
                2'd3 : led <= 4'b0001; 
                default: ;
            endcase
        end
    else if (key[2] == 0) begin
            case (state)
                2'd0 : led <= 4'b1111;
                2'd1 : led <= 4'b0000;
                2'd2 : led <= 4'b1111;
                2'd3 : led <= 4'b0000; 
                default: ;
            endcase
        end
    else if (key[3] == 0) begin
            case (state)
                2'd0 : led <= 4'b1111;
                2'd1 : led <= 4'b1111;
                2'd2 : led <= 4'b1111;
                2'd3 : led <= 4'b1111; 
                default: ;
            endcase
        end
    else 
        led <= led;
end

endmodule

四、效果

---

五、总结

这里的实现并不难，加强了按键与LED的互动性，使用了状态控制LED，槽点就是按键没有进行消抖。

六、参考资料

按键控制led灯