module sr04( input clk , input rst_n , input echo , output wire trig , output echo_d, output [7:0] distance ); parameter INTERVAL = 5_000_000; //100ms reg [22:0] cnt ; reg [24:0] echo_cnt_reg[3:0], echo_cnt; wire [21:0] echo_mean; reg [1:0] addr; reg echo_1,echo_2; wire echo_flag; wire echo_h; assign echo_h = (~echo_2) & echo_1; assign echo_d = (~echo_1) & echo_2; assign trig = (cnt < 500) ? 1 : 0; assign distance = echo_mean * 78 / 1_000_000; assign echo_mean = (echo_cnt_reg[0]+echo_cnt_reg[1]+echo_cnt_reg[2]+echo_cnt_reg[3]) >> 2; always @(posedge clk or negedge rst_n) begin if(!rst_n)begin addr <= 0; echo_cnt_reg[0] <= 0; echo_cnt_reg[1] <= 0; echo_cnt_reg[2] <= 0; echo_cnt_reg[3] <= 0; end else if(echo_d)begin echo_cnt_reg[addr] <= echo_cnt; if(addr == 3) addr <= 0; else addr <= addr + 1; end else begin addr <= addr; echo_cnt_reg[addr] <= echo_cnt_reg[addr]; end end always @(posedge clk or negedge rst_n) begin if(!rst_n)begin cnt <= 0; end else if(cnt == INTERVAL) cnt <= 0; else cnt <= cnt + 1'b1; end always @(posedge clk or negedge rst_n) begin if(!rst_n)begin echo_1 <= 0; echo_2 <= 0; end else begin echo_1 <= echo ; echo_2 <= echo_1; end end always @(posedge clk or negedge rst_n) begin if(!rst_n) echo_cnt <= 0; else if(!cnt) echo_cnt <= 0; else if(echo) echo_cnt <= echo_cnt + 1; else echo_cnt <= echo_cnt; end endmodule 分析其中的核心代码及其功能
时间: 2024-02-14 15:10:47 浏览: 169
这是一个用于超声波测距的模块,其中的核心代码是:
```
assign trig = (cnt < 500) ? 1 : 0;
assign distance = echo_mean * 78 / 1_000_000;
assign echo_mean = (echo_cnt_reg[0]+echo_cnt_reg[1]+echo_cnt_reg[2]+echo_cnt_reg[3]) >> 2;
always @(posedge clk or negedge rst_n) begin
if(!rst_n)begin
addr <= 0;
echo_cnt_reg[0] <= 0;
echo_cnt_reg[1] <= 0;
echo_cnt_reg[2] <= 0;
echo_cnt_reg[3] <= 0;
end
else if(echo_d)begin
echo_cnt_reg[addr] <= echo_cnt;
if(addr == 3)
addr <= 0;
else
addr <= addr + 1;
end
else begin
addr <= addr;
echo_cnt_reg[addr] <= echo_cnt_reg[addr];
end
end
```
其中,`trig`是控制超声波发射的信号,当`cnt`小于500时,`trig`为1,否则为0。`distance`是计算出的距离值,通过将`echo_mean`乘以78再除以1,000,000得到。`echo_mean`是计算出的4个回波信号的平均值,通过将4个寄存器中的值相加除以4得到。
在`always`块中,首先根据`rst_n`信号来进行复位操作;然后根据`echo_d`信号来将当前的回波信号计数值存入对应的寄存器中,同时更新`addr`的值,以便下一次存入另一个寄存器;最后,如果没有回波信号,则不进行操作。
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