05. 基于Verilog的呼吸灯程序设计

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05_led_breath_v0

一个基于Verilog的呼吸灯程序示例，该程序通过PWM（脉冲宽度调制）技术来模拟呼吸灯的效果，逐渐变亮再逐渐变暗的LED灯，给人一种灯光在“呼吸”的感觉。

原理解释：

PWM(脉冲宽度调制)：通过改变输出信号的占空比来模拟不同亮度的LED灯。
呼吸灯周期：呼吸灯的周期由breathing_cnt控制，这里假设周期为1/4秒钟。
呼吸灯亮度变化：呼吸灯的亮度变化通过改变占空比的值来模拟。

当pwm_cnt小于当前pwm_duty时，LED亮；
当pwm_cnt大于pwm_duty时，LED不亮。

知识点：

PWM(脉冲宽度调制)
Duty(占空比)
位宽确定可表达的最大整数值
位拼接语法 assign led = {6{led_breathing}};

module led_breath #(parameter CLK_FREQ = 50000000,parameter LED_ON = 1'b0
)(input wire clk,       input wire rst_n,     output wire [5:0] led      
);// 定义一个计数器用于产生PWM波形
reg [11:0] pwm_cnt;
reg [11:0] pwm_duty;reg [31:0] breath_cnt;// 呼吸灯周期，假设为1秒钟4个周期
localparam CYCLE = CLK_FREQ/4;always @(posedge clk) beginif (!rst_n) breath_cnt <= 0;else beginbreath_cnt <= breath_cnt + 1'b1;if (breath_cnt == CYCLE-1) breath_cnt <= 0;end
endwire breath_done = (breath_cnt == CYCLE-1);//PWM CNT
always @(posedge clk) beginif (!rst_n) pwm_cnt <= 0;else pwm_cnt <= pwm_cnt + 1'b1;
end//PWM Duty
//light to off
always @(posedge clk) beginif (!rst_n) pwm_duty <= 12'hFFF;else if(breath_done) beginif(pwm_duty == 0) pwm_duty <= 12'hFFF;else pwm_duty <= {1'b0,pwm_duty[11:1]};end//else pwm_duty <= pwm_duty;
end/*
//off to light on
always @(posedge clk) beginif (!rst_n) pwm_duty <= 12'b0;else if(breath_done) beginif(pwm_duty == 12'hFFF) pwm_duty <= 12'b0;else pwm_duty <= {pwm_duty[10:0],1'b1};end//else pwm_duty <= pwm_duty;
end
*/// 根据PWM计数器的值和呼吸灯的亮度变化来控制LED的亮度
reg led_breathing;
//parameter LED_ON = 1'b0; //led active low on our board
localparam LED_OFF = ~LED_ON;always @(posedge clk) beginif (!rst_n) led_breathing <= LED_OFF;else if (pwm_cnt < pwm_duty) beginled_breathing <= LED_ON;end else led_breathing <= LED_OFF;
endassign led = {6{led_breathing}};endmodule