模拟波形

• FPGA中使用数字滤波器时，可通过观察模拟波形更好地查看滤波效果。可以通过ModelSim中的波形格式设置来实现更直观的波形显示。
• 右键波形->Format-> Analog
  
• 效果
  

数值格式显示

• 不同的数值格式显示：右键波形->Radix-> Decimal
  
• 效果
  

临时设置格式

• 这个格式可在当前项目的中所有仿真中保持(不关闭窗口的每次重新仿真)，不用向上面一样没测设置https://ww1.microchip.com/downloads/aemDocuments/documents/FPGA/swdocs/modelsim/modelsim_user_2024_2.pdf
  

设置默认值

• 编辑modelsim.ini的DefaultRadix
  

示例代码

verilog

/*
- 输出 是否找到同步头

- 找正峰
    - 尝试找到超过正阈值的点作为潜在的正峰。
    - 对每个可能的正峰，进一步检查它是否是局部最大值（通过比较接下来的12个样本），并记录峰值的位置。

- 验证正峰后的负峰 :
   - 一旦找到一个正峰，检查其后大约18或24个样本处是否存在低于负阈值的负峰。
   - 如果找到了符合条件的负峰，则认为找到了一个同步信号的开始，
*/  

module MySyncDetect (
	input wire reset,
    input wire CLK_for_FIFO,            // 同步FIFO控制信号
    input wire [15:0] DATA_FIR_from_DFIFO, // 来自FIFO的数据流
    input wire full_from_DFIFO,         // FIFO满标志
    input wire [11:0] usedw_from_DFIFO, // FIFO已用深度
    output reg sync_detected,           // 是否找到同步头
	 output reg[2:0] state               // 状态机状态
);

parameter SYNCLEN = 64;               // 同步长度参数，可以根据实际情况调整
parameter POS_THRESHOLD = 100;        // 正阈值
parameter NEG_THRESHOLD = -100;       // 负阈值
localparam DEPTH = 32;                // 数据缓冲区深度
localparam FIND_RANGE = 20;           // 数据缓冲区深度

// 状态机定义
localparam IDLE = 3'b000;
localparam FIND_PEAK = 3'b001;
localparam CHECK_NEGATIVE_PEAK = 3'b010;
localparam SYNC_FOUND = 3'b011;
// reg [2:0] state;
reg [2:0] next_state;

reg [15:0] data_buffer[0:DEPTH-1];    // 数据缓冲区
reg [4:0] buffer_index;               // 缓冲区索引
reg [4:0] peak_index;                 // 峰值索引
reg bPeak;                            // 是否找到峰值
reg bFirstTag;                        // 第一个标签标记

integer i=0;
integer j;
integer k;

// 初始化状态
 always @(posedge reset) begin
        if (reset) begin
            state = IDLE;
	 		next_state = IDLE;
	 		buffer_index = 5'b0;
        end
end


// 控制信号
wire valid_data = (usedw_from_DFIFO > 0);// && !full_from_DFIFO;
wire [15:0] current_data = DATA_FIR_from_DFIFO;

// 时钟边沿触发过程
always @(posedge CLK_for_FIFO) begin
    if (valid_data) begin
        // 更新数据缓冲区
        data_buffer[buffer_index] <= current_data;
        buffer_index <= (buffer_index == DEPTH-1) ? 0 : buffer_index + 1;
    end
    
    // 状态机转换
    state <= next_state;
end

// 下一状态逻辑
always @(posedge CLK_for_FIFO) begin
    // next_state = state;
    case (state)
        IDLE: begin
            if (valid_data)
                next_state = FIND_PEAK;
        end
        
        FIND_PEAK: begin
            // 查找正峰
				if(buffer_index>= 12)begin
					i = buffer_index-12;
				end 
				else begin 
					i = buffer_index + DEPTH - 12;
				end
					
				 if (data_buffer[i] > POS_THRESHOLD) begin
					  // 确认是否为局部最大值
					  bPeak = 1;
					  for (j = 1; j < 12; j = j + 1) begin
							if (data_buffer[(i+j) % DEPTH] > data_buffer[i]) begin
								 bPeak = 0;
							end
					  end

					  // 是局部最大值
					  if (bPeak) begin
							peak_index = i;
							next_state = CHECK_NEGATIVE_PEAK;
					  end
              end
        end
        
        CHECK_NEGATIVE_PEAK: begin
            // 验证正峰后的负峰
            for (k = 18; k <= 24; k = k + 1) begin
                if (data_buffer[(peak_index+k) % DEPTH] < NEG_THRESHOLD) begin
                    // 找到符合条件的负峰
                    next_state = SYNC_FOUND;
                end
            end
        end
        
        SYNC_FOUND: begin
            // 已经找到同步头
            next_state = IDLE;
        end
    endcase
end

// 输出逻辑
always @(posedge CLK_for_FIFO) begin
    sync_detected <= 0;
    case (state)
        SYNC_FOUND: begin
            sync_detected <= 1;
        end
        default: begin
            sync_detected <= 0;
        end
    endcase
end

endmodule

tb

// Testbench for SyncDetect

`timescale 1ns/1ps

module MySyncDetect_tb;
    // Inputs
    reg CLK_for_FIFO;
    reg [15:0] DATA_from_DFIFO;
    reg full_from_DFIFO;
    reg [11:0] usedw_from_DFIFO;
	 integer i;
    // Output
    wire sync_detected;
	 wire[2:0] state;

    // Instantiate the Unit Under Test (UUT)
    M2SyncDetect uut (
        .CLK_for_FIFO(CLK_for_FIFO),
        .DATA_FIR_from_DFIFO(DATA_from_DFIFO),
        .full_from_DFIFO(full_from_DFIFO),
        .usedw_from_DFIFO(usedw_from_DFIFO),
        .sync_detected(sync_detected),
		  .state(state)
    );

    // Clock generation
    initial begin
        CLK_for_FIFO = 0;
        forever #5 CLK_for_FIFO = ~CLK_for_FIFO; // 10 ns clock period
    end

    // Stimulus
	 initial begin
        // Initialize inputs
        DATA_from_DFIFO = -16'd23000;
        full_from_DFIFO = 0;
        usedw_from_DFIFO = 12'd0;
		  
		  // Apply test cases
        #100;
        DATA_from_DFIFO = -16'd23000; // Example data
        usedw_from_DFIFO = 12'd1;

        #20;
        DATA_from_DFIFO = -16'd1; // Example data
        usedw_from_DFIFO = 12'd2;

        #30;
        DATA_from_DFIFO = 16'h1234; // Example data
        usedw_from_DFIFO = 12'd3;

        #50;
        DATA_from_DFIFO = 16'hDEAD; // Example data
        usedw_from_DFIFO = 12'd4;

        // Apply test cases
        #10;
        for (i = 0; i < 5; i = i + 1) begin
            DATA_from_DFIFO = -16'd23000 + i; // Example data with variation
            full_from_DFIFO = (i % 2 == 0) ? 1 : 0;
            usedw_from_DFIFO = 12'd100 + i * 10;
            #20;
        end
		  
		  for (i = 0; i < 20; i = i + 1) begin
            DATA_from_DFIFO = -16'd23000 + i*10; // Example data with variation
            #20;
        end

        #50;
        $stop; // End simulation
		  
		  
		  		  // Apply test cases
        #100;
        DATA_from_DFIFO = -16'd23000; // Example data
        usedw_from_DFIFO = 12'd1;

        #20;
        DATA_from_DFIFO = -16'd1; // Example data
        usedw_from_DFIFO = 12'd2;

        #30;
        DATA_from_DFIFO = 16'h1234; // Example data
        usedw_from_DFIFO = 12'd3;

        #50;
        DATA_from_DFIFO = 16'hDEAD; // Example data
        usedw_from_DFIFO = 12'd4;

        // Apply test cases
        #10;
        for (i = 0; i < 5; i = i + 1) begin
            DATA_from_DFIFO = -16'd23000 + i; // Example data with variation
            full_from_DFIFO = (i % 2 == 0) ? 1 : 0;
            usedw_from_DFIFO = 12'd100 + i * 10;
            #20;
        end
		  
		  for (i = 0; i < 20; i = i + 1) begin
            DATA_from_DFIFO = -16'd23000 + i*10; // Example data with variation
            #20;
        end
    end

endmodule