圖像流AXI-Stream生成BMP文件的實現(xiàn)思路

實現(xiàn)思路

在實現(xiàn)上，由于bmp除去文件頭后也只是把圖像流數(shù)據(jù)按順序放而已，所以這里

1. 先用一個fifo緩存圖像數(shù)據(jù)
2. 寫一個狀態(tài)機控制按順序輸出文件頭和數(shù)據(jù)。
3. 注意fifo的讀寫和AXIS之間的握手和控制邏輯。因為看起來fifo是暫存數(shù)據(jù)的，但可預見fifo應該是有可能周期性空的，因為在每行的結束后tlast都是讓valid拉低一個周期，這一小個周期在行多了之后一點會抵消文件頭的大小。

生成緩存fifo

聲明：

1. 命名并不規(guī)范
2. 可以用原語（xpm）或其他同類型IP生成，這里不多贅述。

在IP catalog的搜索框中寫fifo，選FIFO Generator：

具體按下面設置：

這里注意必須選擇First Word Fall Through

選25位是因為，在數(shù)據(jù)結構上是1tuser + 2*8 data，選擇把幀開始標志也丟進fifo可以避免錯幀。

總體端口

生成的BMP文件依然以AXIS格式輸出，在tb中再以二進制格式寫進文件：

module axis2bmp#(
    parameter PIC_HEIGHT = 1080,
    parameter PIC_WIDTH  = 1920
)(
    // global signal
    input clk_i,    // clock
    input rst_n_i,  // reset

    // axi stream (slave) interface signal - > pixel data
    input  [23:0] s_axis_video_tdata,   // DATA
    input  [0:0] s_axis_video_tvalid,  // VALID
    output [0:0] s_axis_video_tready,  // READY
    input  [0:0] s_axis_video_tuser,   // SOF
    input  [0:0] s_axis_video_tlast,    // EOL

    // axi stream (master) interface signal - > bmp
    output reg [23:0] m_axis_video_tdata,   // DATA
    output [ 0:0] m_axis_video_tvalid,  // VALID
    input  [ 0:0] m_axis_video_tready,  // (meaningless)
    output [ 0:0] m_axis_video_tlast    // end of file stream
);

slave端為圖像數(shù)據(jù),master端為輸出BMP文件流,這里需要注意master流中并不處理反壓問題(即沒有ready信號,懶得加fifo)

fifo接口邏輯

// image pixel fifo dw=24, BRAM cap=512
wire [24:0] bmp_header_din;
wire [0:0] bmp_header_wr;
wire [0:0] bmp_header_full;

wire [0:0] bmp_header_empty;
wire [0:0] bmp_header_rd;
wire [24:0] bmp_header_dout;

bmp_header bmp_header_inst (
    .clk(clk_i),      // input wire clk
    .srst(~rst_n_i),    // input wire srst
    .din(bmp_header_din),      // input wire [23 : 0] din
    .wr_en(bmp_header_wr),  // input wire wr_en
    .rd_en(bmp_header_rd),  // input wire rd_en
    .dout(bmp_header_dout),    // output wire [23 : 0] dout
    .full(bmp_header_full),    // output wire full
    .empty(bmp_header_empty)  // output wire empty
);

// pixel fifo assignment
assign bmp_header_din = {s_axis_video_tuser,s_axis_video_tdata};
assign s_axis_video_tready = ~bmp_header_full;
assign bmp_header_wr = s_axis_video_tready && s_axis_video_tvalid;

fifo的讀使能放到后面再講,這里先處理好數(shù)據(jù)進來就可以了

文件流處理狀態(tài)機

經(jīng)典三板斧，不展開

包頭數(shù)據(jù)準備

需要搬回第一篇中的BMP文件格式,由于是輸出,所以我們就不考慮調(diào)色板了：

這里先用一些localparam存起來，（這里考慮大小不變）

//--------------------------寫B(tài)MP狀態(tài)機------------------------

// local parameter
localparam [15:0] bfType = 16'h4d42;
localparam [31:0] bfReserved = 32'h0000_0000;
localparam [31:0] biSizeImage = PIC_HEIGHT * PIC_WIDTH * 3;
localparam [31:0] biSizeImage_cnt = PIC_HEIGHT * PIC_WIDTH;
localparam [31:0] bfOffset = 32'd54;
localparam [31:0] bfSize = biSizeImage + bfOffset;

localparam [31:0] biSize = 32'h28;
localparam [31:0] biWidth = PIC_WIDTH;
localparam [31:0] biHeight = PIC_HEIGHT;

localparam [15:0] biPlanes = 16'd1;
localparam [15:0] biBitCount = 16'd24;
localparam [31:0] biCompression = 32'd0;
localparam [127:0] biUseless = 128'd0;

localparam   CNT_PIXEL  = $clog2(PIC_HEIGHT*PIC_WIDTH);

轉(zhuǎn)移狀態(tài)

//轉(zhuǎn)移狀態(tài)
localparam S_WAIT               = 3'b001 ;  // 等待SOF標記
localparam S_WRITE_HEADER       = 3'b010 ;  // 寫B(tài)MP包頭
localparam S_WRITE_DATA         = 3'b100 ;  // 寫B(tài)MP數(shù)據(jù)

狀態(tài)轉(zhuǎn)移變量

//狀態(tài)轉(zhuǎn)移變量
reg [2:0] state, n_state;       // 狀態(tài)寄存器
reg [4:0] header_cnt;           // 包頭計數(shù)器
reg [CNT_PIXEL-1:0] pixel_cnt;  // 像素計數(shù)器

wire frame_start = bmp_header_dout[24];    // SOF flag
wire write_header_done = (header_cnt == 5'd17);     // 18 -1 - > 18*3
wire write_pixel_done = (pixel_cnt == biSizeImage_cnt -1'b1);

這里需要注意 : 兩個狀態(tài)只由計數(shù)器指定跳轉(zhuǎn)

狀態(tài)轉(zhuǎn)移

//狀態(tài)機初始化
always @ (posedge clk_i) begin
    if(~rst_n_i)
        state <= S_WAIT;
    else
        state <= n_state;
end

狀態(tài)機 狀態(tài)轉(zhuǎn)移

always @ (*) begin
    case(state)
        S_WAIT :
            if(frame_start)
                n_state = S_WRITE_HEADER;
        else
            n_state = S_WAIT;
        S_WRITE_HEADER:
            if(write_header_done)
                n_state = S_WRITE_DATA;
        else
            n_state = S_WRITE_HEADER;
        S_WRITE_DATA:
            if(write_pixel_done)
                n_state = S_WAIT;
        else
            n_state = S_WRITE_DATA;
        default:
            n_state = S_WAIT;
    endcase
end

寫B(tài)MP包頭 處理邏輯

這里直接按照文件格式,用計數(shù)器懟進去進行:

always @(posedge clk_i or negedge  rst_n_i) begin
    if (~rst_n_i)
        header_cnt <= 5'd0;
    else if(state == S_WRITE_HEADER && header_cnt < 5'd17)
        header_cnt <= header_cnt + 1'd1;
    else
        header_cnt <= 5'd0;
end

在數(shù)據(jù)上,可參考(注意數(shù)據(jù)以小端輸出):

case (header_cnt)
    5'd0 :
        m_axis_video_tdata = {bfSize[0+:8], bfType};
    5'd1 :
        m_axis_video_tdata = bfSize[8+:24];
    5'd2 :
        m_axis_video_tdata = bfReserved[0 +:24];
    5'd3 :
        m_axis_video_tdata = {bfOffset[0+:16],bfReserved[24+:8]};
    5'd4 :
        m_axis_video_tdata = {biSize[0+:8], bfOffset[16+:16]};
    5'd5 :
        m_axis_video_tdata = biSize[8+:24];
    5'd6 :
        m_axis_video_tdata = biWidth[0+:24];
    5'd7 :
        m_axis_video_tdata = {biHeight[0+:16],biWidth[24+:8]};
    5'd8 :
        m_axis_video_tdata = {biPlanes[0+:8],biHeight[16+:16]};
    5'd9 :
        m_axis_video_tdata = {biBitCount[0+:16],biPlanes[8+:8]};
    5'd10 :
        m_axis_video_tdata = biCompression[0+:24];
    5'd11 :
        m_axis_video_tdata = {biSizeImage[0+:16],biCompression[24+:8]};
    5'd12 :
        m_axis_video_tdata = {biUseless[0+:8], biSizeImage[16+:16]};
    5'd13 :
        m_axis_video_tdata = biUseless[8+:24];
    5'd14 :
        m_axis_video_tdata = biUseless[32+:24];
    5'd15 :
        m_axis_video_tdata = biUseless[56+:24];
    5'd16 :
        m_axis_video_tdata = biUseless[80+:24];
    5'd17 :
        m_axis_video_tdata = biUseless[104+:24];
    default:
        m_axis_video_tdata = 24'heeeeee;
endcase

其中+:和-:語法簡介可以翻看筆者之前的文章或自行百度。這里這樣寫是為了看位寬方便一點

寫圖像數(shù)據(jù)

這里直接放開fifo數(shù)據(jù)就可以了,注意握手邏輯:

計數(shù)器邏輯:

always @(posedge clk_i or negedge  rst_n_i) begin
    if (~rst_n_i)
        pixel_cnt <= 'd0;
    else if(state == S_WRITE_DATA && pixel_cnt < biSizeImage_cnt-1) begin
        if(bmp_header_empty)
            pixel_cnt <= pixel_cnt;
        else
            pixel_cnt <= pixel_cnt + 1'd1;
    end
    else
        pixel_cnt <= 'd0;
end

數(shù)據(jù)放行:

assign bmp_header_rd = ((state == S_WRITE_DATA) && ~bmp_header_empty) 
           || ((state == S_WAIT) && ~frame_start);

………………
else if(state == S_WRITE_DATA) begin
    m_axis_video_tdata = bmp_header_dout;
end
………………

這里上下兩塊合成一個組合邏輯就變成m_axis_video_tdata的完整控制邏輯了

仿真tb編寫

這里由前面的積累就比較簡單,直接將上一節(jié)生成的AXIS輸入例化即可:

定義localparam

// Parameters
localparam  data_out = "./a_ch.txt";
localparam  bmp_path = "./test.bmp";
localparam  bmp_path_out = "./test_out.bmp";
localparam  height = 1080;
localparam  width = 1920;

這里如果輸入輸出不一樣可以在tb中分開定義

簡單引個線

// AXI-Stream Ports
wire [0:0] m_axis_tvalid;
wire [0:0] m_axis_tready;
wire [23:0] m_axis_tdata;
wire [0:0] m_axis_tlast;
wire [0:0] m_axis_tuser;

bmp_tb
#(
    .data_out(data_out ),
    .bmp_path(bmp_path ),
    .height(height ),
    .width (width )
)
bmp_tb_dut (
    .clk_i (clk_i ),
    .rst_n_i (rst_n_i ),
    .m_axis_tvalid (m_axis_tvalid ),
    .m_axis_tready (m_axis_tready ),
    .m_axis_tdata (m_axis_tdata ),
    .m_axis_tlast (m_axis_tlast ),
    .m_axis_tuser  ( m_axis_tuser)
);


wire [23:0] m_axis_video_tdata;  //這才是想要的信號
wire [ 0:0] m_axis_video_tvalid;
wire [ 0:0] m_axis_video_tlast;

axis2bmp
#(
    .PIC_HEIGHT(height ),
    .PIC_WIDTH (width )
)
axis2bmp_dut (
    .clk_i (clk_i ),
    .rst_n_i (rst_n_i ),
    .s_axis_video_tdata (m_axis_tdata ),
    .s_axis_video_tvalid (m_axis_tvalid ),
    .s_axis_video_tready (m_axis_tready ),
    .s_axis_video_tuser (m_axis_tuser ),
    .s_axis_video_tlast (m_axis_tlast ),
    .m_axis_video_tdata (m_axis_video_tdata ),
    .m_axis_video_tvalid (m_axis_video_tvalid ),
    .m_axis_video_tready (1'b1 ),
    .m_axis_video_tlast  ( m_axis_video_tlast)
);

文件流寫入

這里直接用$fwrite一個一個字節(jié)寫進去就可以了:

integer iBmpFileId;
initial begin
    begin
        iBmpFileId = $fopen(bmp_path_out,"wb");
        #10 rst_n_i = 1'b0;
        #200 rst_n_i = 1'b1;

        while (!m_axis_video_tlast) begin
            @(negedge clk_i) ;
            if(m_axis_video_tvalid==1'b1)begin
                $fwrite(iBmpFileId, "%c", m_axis_video_tdata[7-:8]) ;
                $fwrite(iBmpFileId, "%c", m_axis_video_tdata[15-:8]) ;
                $fwrite(iBmpFileId, "%c", m_axis_video_tdata[23-:8]);
            end
        end
        $fclose(iBmpFileId);
        #2000;
        $finish;
    end
end

然后在sim_x-> behav -> xsim下面放好圖像就可以了。