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 [:] cnt;
     reg [:] cnt1_pwm = 'd2, cnt2_pwm = 21'd52_4288;
     reg [:] cnt_s;

     always @ (posedge clk, negedge rst)
         if (!rst)
             begin
                 cnt_s <= ;
                 cnt1_pwm <= 'd1;
                 cnt2_pwm <= 'd52_4288;
             end
         else if (cnt_s == 'd1000_0000) //计0.2秒
             begin
                 cnt_s <= ;
                     cnt1_pwm <= {cnt1_pwm[:], cnt1_pwm[]}; //调节脉宽
                     cnt2_pwm <= {cnt2_pwm[], cnt2_pwm[:]};

                     //cnt1_pwm <= (cnt1_pwm >> 2)|(cnt1_pwm << 19);//right
                     //cnt2_pwm <= (cnt2_pwm << 2)|(cnt2_pwm >> 19);//left
             end
         else
             cnt_s <= cnt_s + ;

     //
     always @ (posedge clk, negedge rst)
         if (!rst)
             cnt <= 'h0;
         else if (cnt == 'd55_0000)  //一个周期
             cnt <= 'b0;
         else
             cnt <= cnt + 'b1;

     //    pwm生成
     always @ (posedge clk, negedge rst)
         if (!rst)
             out1 <= 'b0;
         else if (cnt <= cnt1_pwm)
             out1 <= 'b0;
         else
             out1 <= 'b1;

     always @ (posedge clk, negedge rst)
         if (!rst)
             out2 <= 'b0;
         else if (cnt <= cnt2_pwm)
             out2 <= 'b0;
         else
             out2 <= 'b1;

     assign out3 = 'b0;
     assign out4 = 'b0;

 endmodule