13. 串口接收模块的项目应用案例

1. 使用串口来控制LED灯工作状态

使用串口发送指令到FPGA开发板，来控制第7课中第4个实验的开发板上的LED灯的工作状态。

LED灯的工作状态：让LED灯按指定的亮灭模式亮灭，亮灭模式未知，由用户指定，8个变化状态为一个循环，每个变化状态的时间值可以根据不同的应用场景来选择。

1.1 原理如下

1.2 任务简化为：

如何使用串口接收8个字节的数据，判断并输出其中的数据。

2. 写设计代码，仿真代码并仿真

2.1 设计代码（重要）

1.在完成uart_cmd解析数据模块时，要掌握移位寄存器的使用，以及延后一拍判定的方法

2.修改了uart_byte_rx1串口接收模块代码，修改了rx_data八位数据接收条件，原先是发送了在出现tx_done信号后得到输出八位数据，这样会导致我们在后续模块通过tx_done信号接收数据时接收的是前一个八位数据。现在改为了tx_done信号出现时，八位数据已准备输出了。

3.修改了counter_led灯模块代码

module uart_rx_ctrl_led(clk,rstn,uart_rx,blaud_set,led
);input clk;input rstn;input uart_rx;input [2:0]blaud_set;output led;wire [7:0]data;wire rx_done;wire [7:0] ctrl;wire [31:0] times;uart_byte_rx1 uart_byte_rx1_inst(.clk(clk),.rstn(rstn),.blaud_set(blaud_set),.uart_rx(uart_rx),.data(data),.rx_done(rx_done));uart_cmd uart_cmd_inst(.clk(clk),.rstn(rstn),.rx_data(data),.rx_done(rx_done),.ctrl(ctrl),.times(times));counter_led4 counter_led4_inst(.clk(clk),.rstn(rstn),.ctrl(ctrl),.times(times),.led(led));endmodule

module uart_byte_rx1(clk,rstn,blaud_set,uart_rx,data,rx_done
);input clk;input rstn;input [2:0]blaud_set;input uart_rx;output reg [7:0] data;output rx_done;reg [8:0] bps_dr;always@(*)case(blaud_set)0:bps_dr = 1000000000/9600/16/20;1:bps_dr = 1000000000/19200/16/20;2:bps_dr = 1000000000/38400/16/20;3:bps_dr = 1000000000/57600/16/20;4:bps_dr = 1000000000/115200/16/20;default : bps_dr = 1000000000/9600/16/20;endcase//边沿信号检测reg [1:0] uart_rx_r; //用两位寄存器分别存储两个时间沿的uart_rx信号always@(posedge clk) beginuart_rx_r[0] <= uart_rx;uart_rx_r[1] <= uart_rx_r[0];end//将两位寄存器的值直接通过导线输出进行判断（不需要再使用寄存器）wire nedge_uart_rx;  //掌握一下这个方法，之前一直使用的是寄存器//法一：//assign nedge_uart_rx = ((uart_rx_r[0] == 0)&&(uart_rx_r == 1));//法二：assign nedge_uart_rx = (uart_rx_r == 2'b10);reg rx_en;always@(posedge clk or negedge rstn)if(!rstn)rx_en <= 0;else if(nedge_uart_rx)rx_en <= 1;else if(rx_done)rx_en <= 0;//周期计数器reg [8:0] div_cnt;always@(posedge clk or negedge rstn)if(!rstn)div_cnt <= 0;else if(rx_en) beginif(div_cnt == bps_dr - 1)div_cnt <= 0;elsediv_cnt <= div_cnt + 1'd1;endelsediv_cnt <= 0;wire [3:0]bps_clk_16x; //（一定要记得加位宽）采样信号，这种写法很灵活assign bps_clk_16x = bps_dr/2; //采样每一段的中点值，同时也可以用它来计数。//发送一字节的数据有需要十个数据位，每位数据有16个小段供采样,共160reg [7:0]bps_cnt;always@(posedge clk or negedge rstn)if(!rstn)bps_cnt <= 0;else if(rx_en) beginif(bps_cnt == 159)bps_cnt <= 0;else if(div_cnt ==bps_clk_16x)bps_cnt <= bps_cnt + 1'd1; endelse  bps_cnt <= 0;reg[2:0] r_data[7:0];//二维数据，代表八个r_data，每个r_data有3位寄存器存储数值。reg[2:0] sta_data;reg[2:0] sto_data;always@(posedge clk or negedge rstn)if(!rstn)beginsta_data <= 0;sto_data <= 0;r_data[0] <= 0; //语法规定，二维数组赋值要分开赋值r_data[1] <= 0;    r_data[2] <= 0;r_data[3] <= 0;    r_data[4] <= 0;  r_data[5] <= 0;    r_data[6] <= 0; r_data[7] <= 0;        endelse if(div_cnt == bps_clk_16x - 1)case(bps_cnt) //下面合在一起的写法是允许的0:beginr_data[0] <= 0; r_data[1] <= 0;    r_data[2] <= 0;r_data[3] <= 0;    r_data[4] <= 0;  r_data[5] <= 0;    r_data[6] <= 0; r_data[7] <= 0;end   5,6,7,8,9,10,11: sta_data <= sta_data + uart_rx;21,22,23,24,25,26,27: r_data[0] <= r_data[0] + uart_rx;37,38,39,40,41,42,43: r_data[1] <= r_data[1] + uart_rx;53,54,55,56,57,58,59: r_data[2] <= r_data[2] + uart_rx;69,70,71,72,73,74,75: r_data[3] <= r_data[3] + uart_rx;85,86,87,88,89,90,91: r_data[4] <= r_data[4] + uart_rx;101,102,103,104,105,106,107: r_data[5] <= r_data[5] + uart_rx;117,118,119,120,121,122,123: r_data[6] <= r_data[6] + uart_rx;133,134,135,136,137,138,139: r_data[7] <= r_data[7] + uart_rx;149,150,151,152,153,154,155: sto_data <= sto_data + uart_rx;default:;endcase        reg rx_done;always@(posedge clk or negedge rstn)if(!rstn)rx_done <= 0;else if(bps_cnt == 159) beginrx_done <= 1;endelserx_done <= 0;//数据接收完成后赋值给data输出always@(posedge clk or negedge rstn)if(!rstn)data <= 0;else if(bps_cnt == 159)begin //修改了之前的判定条件（重要）data[0] <= (r_data[0] >= 4 ) ? 1 : 0;data[1] <= (r_data[1] >= 4 ) ? 1 : 0;data[2] <= (r_data[2] >= 4 ) ? 1 : 0;data[3] <= (r_data[3] >= 4 ) ? 1 : 0;data[4] <= (r_data[4] >= 4 ) ? 1 : 0;data[5] <= (r_data[5] >= 4 ) ? 1 : 0;data[6] <= (r_data[6] >= 4 ) ? 1 : 0;data[7] <= (r_data[7] >= 4 ) ? 1 : 0;end// data[1] <= r_data[1][2]// 0:3'd000// 1:3'd001// 2:3'd010// 4:3'd100// 5:3'd101// 6:3'd110// 7:3'd111 利用第3位的区别给data赋值endmodule

module uart_cmd(clk,rstn,rx_data,rx_done,ctrl,times
);input clk;input rstn;input [7:0]rx_data;input rx_done;output reg[7:0]ctrl;output reg[31:0]times;reg [7:0] data_str[7:0];always@(posedge clk)if(rx_done)begindata_str[7] <= rx_data;data_str[6] <= data_str[7];data_str[5] <= data_str[6];data_str[4] <= data_str[5];data_str[3] <= data_str[4];data_str[2] <= data_str[3];data_str[1] <= data_str[2];data_str[0] <= data_str[1];end//  使判断并取数据的触发条件在存数据的后一拍
//    reg r_rx_done;
//    always@(posedge clk)
//    if(rx_done)
//        r_rx_done <= rx_done;reg r_rx_done;always@(posedge clk)if(rx_done)r_rx_done <= 1;else r_rx_done <= 0;always@(posedge clk or negedge rstn)if(!rstn)begintimes <= 0;ctrl <= 0;endelse if(r_rx_done)if((data_str[0] == 8'h55) && (data_str[1] == 8'hA5) && (data_str[7] == 8'hF0))begintimes[7:0] <= data_str[2];times[15:8] <= data_str[3];times[23:16] <= data_str[4];times[31:24] <= data_str[5];ctrl[7:0] <= data_str[6];endelse beginctrl <= ctrl;times <= times;end
endmodule

module counter_led4(clk,rstn,ctrl,times,led
);input clk;input rstn;input [7:0] ctrl; input [31:0] times; output reg led;reg[31:0] counter;always@(posedge clk or negedge rstn)if(!rstn)counter <= 0;
//为了防止times为0时减1会得到非常到的数值导致归0时间很长（重要）else if(counter >= times - 1'd1) counter <= 0;elsecounter <= counter + 1'd1;reg [2:0]counter2;always@(posedge clk or negedge rstn)if(!rstn)counter2 <= 0;else if(counter == times - 1'd1)counter2 <= counter2 + 1'd1;always@(posedge clk or negedge rstn)if(!rstn)  led <= 0;else case(counter2)0 : led <= ctrl[0];1 : led <= ctrl[1];2 : led <= ctrl[2];3 : led <= ctrl[3];4 : led <= ctrl[4];5 : led <= ctrl[5];6 : led <= ctrl[6];7 : led <= ctrl[7];default : led <= led;endcaseendmodule

2.2 仿真代码

`timescale 1ns / 1psmodule uart_rx_ctrl_led_tb();reg clk;reg rstn;reg uart_rx;wire led;wire [2:0]blaud_set;assign blaud_set = 3'd4;uart_rx_ctrl_led uart_rx_ctrl_led_inst(.clk(clk),.rstn(rstn),.uart_rx(uart_rx),.blaud_set(blaud_set),.led(led));initial clk = 1;always #10 clk = ~clk;initial beginrstn = 0;uart_rx = 1;#201;rstn = 1;#200;uart_tx_byte(8'h55);#90000;uart_tx_byte(8'ha5);#90000;uart_tx_byte(8'h9a);#90000;uart_tx_byte(8'h78);#90000;uart_tx_byte(8'h56);#90000;uart_tx_byte(8'h34);#90000;uart_tx_byte(8'h21);#90000;uart_tx_byte(8'hf0);#90000;$stop;endtask uart_tx_byte;input [7:0] tx_data;beginuart_rx = 1;#20;uart_rx = 0;#8680;uart_rx = tx_data[0];#8680;uart_rx = tx_data[1];#8680;uart_rx = tx_data[2];#8680;uart_rx = tx_data[3];#8680;uart_rx = tx_data[4];#8680;uart_rx = tx_data[5];#8680;uart_rx = tx_data[6];#8680;uart_rx = tx_data[7];endendtaskendmodule

仿真波形