PWM----调节LED亮度

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--调节两个LED灯亮度

module led_pwm (
    clk, 
    rst, 
//cnt1_pwm, 
    out1,
    out2,
    out3,
    out4
);

    input clk, rst;
    //input [19:0] count_pwm;
    output reg out1, out2;
    output out3, out4;
    
    reg [19:0] cnt;
    reg [19:0] cnt1_pwm = 21'd2, cnt2_pwm = 21'd52_4288;
    reg [25:0] cnt_s;
    
    always @ (posedge clk, negedge rst)
        if (!rst)
            begin 
                cnt_s <= 0;
                cnt1_pwm <= 21'd1;
                cnt2_pwm <= 21'd52_4288;
            end 
        else if (cnt_s == 26'd1000_0000) //计0.2秒
            begin 
                cnt_s <= 0;
                    cnt1_pwm <= {cnt1_pwm[18:0], cnt1_pwm[19]}; //调节脉宽
                    cnt2_pwm <= {cnt2_pwm[0], cnt2_pwm[19:1]};
                        
                    //cnt1_pwm <= (cnt1_pwm >> 2)|(cnt1_pwm << 19);//right
                    //cnt2_pwm <= (cnt2_pwm << 2)|(cnt2_pwm >> 19);//left
            end 
        else 
            cnt_s <= cnt_s + 1;
            
    //
    always @ (posedge clk, negedge rst)
        if (!rst)
            cnt <= 21'h0;
        else if (cnt == 21'd55_0000)  //一个周期
            cnt <= 21'b0;
        else 
            cnt <= cnt + 1'b1;
            
    
    //    pwm生成
    always @ (posedge clk, negedge rst)
        if (!rst)
            out1 <= 1'b0;
        else if (cnt <= cnt1_pwm)
            out1 <= 1'b0;
        else
            out1 <= 1'b1;
            
    always @ (posedge clk, negedge rst)
        if (!rst)
            out2 <= 1'b0;
        else if (cnt <= cnt2_pwm)
            out2 <= 1'b0;
        else
            out2 <= 1'b1;
            
    assign out3 = 1'b0;
    assign out4 = 1'b0;
    
endmodule