VGA协议实践

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前言

VGA的全称是Video Graphics Array,即视频图形阵列，是一个使用模拟信号进行视频传输的标准。早期的
CRT显示器由于设计制造上的原因，只能接收模拟信号输入，因此计算机内部的显卡负责进行数模转换,而
VGA接口就是显卡上输出模拟信号的接口。如今液晶显示器虽然可以直接接收数字信号，但是为了兼容显卡上
的VGA接口，也大都支持VGA标准。

环境：

1、Quartus 18.1
2、EP4CE115F29C7
3、vscode

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一、VGA接口定义与传输原理

1、VGA接口定义

2、传输原理

从上面两幅图中我们可以看到VGA传输过程中的行同步时序和场同步时序非常类似，一行或一场(又称一帧)数据都分为四个部分:低电平同步脉冲、显示后沿、有效数据段以及显示前沿。
行同步信号HSYNC在一个行扫描周期中完成一行图像的显示，其中在a段维持一段时间的低电平用于 数据同
步，其余时间拉高;在有效数据期间(c段) ，红绿蓝三原色数据通道上输出一-行图像信号,其余时间数据无
效。与之类似，场同步信号在在一个场扫描周期中完成一 帧图像的显示， 不同的是行扫描周期的基本单位是像素点时钟，即完成一个像素点显示所需要的时间;而场扫描周期的基本单位是完成一-行图像 显示所需要的时间。

3、不同分辨率对应不同参数

二、Verilog编程

1）屏幕上显示彩色条纹
2）显示自定义的汉字字符（姓名-学号）
3）输出一幅彩色图像
4) 将行、场同步信号中，故意分别加入一定 ms延时（用delay命令），观察会出现什么现象。

1、VGA显示彩色条纹

• 代码：

module vga_dirve (input			wire						clk,            //系统时钟
                  input			wire						rst_n,          //复位
                  input			wire		[ 15:0 ]		rgb_data,       //16位RGB对应值
                  output			wire							vga_clk,    //vga时钟 25M
                  output			reg							h_sync,     //行同步信号
                  output			reg							v_sync,     //场同步信号
                  output			reg		[ 11:0 ]				addr_h, //行地址
                  output			reg		[ 11:0 ]				addr_v,  //列地址
                  output			wire		[ 4:0 ]				rgb_r,  //红基色
                  output			wire		[ 5:0 ]				rgb_g,  //绿基色
                  output			wire		[ 4:0 ]				rgb_b  //蓝基色
);

// 640 * 480 60HZ
localparam	 H_FRONT = 16; // 行同步前沿信号周期长
localparam	 H_SYNC  = 96; // 行同步信号周期长
localparam	 H_BLACK = 48; // 行同步后沿信号周期长
localparam	 H_ACT   = 640; // 行显示周期长
localparam	 V_FRONT = 11; // 场同步前沿信号周期长
localparam	 V_SYNC  = 2; // 场同步信号周期长
localparam	 V_BLACK = 31; // 场同步后沿信号周期长
localparam	 V_ACT   = 480; // 场显示周期长

// 800 * 600 72HZ
// localparam	 H_FRONT = 40; // 行同步前沿信号周期长
// localparam	 H_SYNC  = 120; // 行同步信号周期长
// localparam	 H_BLACK = 88; // 行同步后沿信号周期长
// localparam	 H_ACT   = 800; // 行显示周期长
// localparam	 V_FRONT = 37; // 场同步前沿信号周期长
// localparam	 V_SYNC  = 6; // 场同步信号周期长
// localparam	 V_BLACK = 23; // 场同步后沿信号周期长
// localparam	 V_ACT   = 600; // 场显示周期长


localparam	H_TOTAL = H_FRONT + H_SYNC + H_BLACK + H_ACT; // 行周期
localparam	V_TOTAL = V_FRONT + V_SYNC + V_BLACK + V_ACT; // 列周期

reg			[ 11:0 ]			cnt_h			; // 行计数器
reg			[ 11:0 ]			cnt_v			; // 场计数器
reg			[ 15:0 ]			rgb			; // 对应显示颜色值

// 对应计数器开始、结束、计数信号
wire							flag_enable_cnt_h			;
wire							flag_clear_cnt_h			;
wire							flag_enable_cnt_v			;
wire							flag_clear_cnt_v			;
wire							flag_add_cnt_v  			;
wire							valid_area      			;


// 25M时钟 行周期*场周期*刷新率 = 800 * 525* 60
wire							clk_25			;
// 50M时钟 1040 * 666 * 72
wire							clk_50			;
//PLL
pll	pll_inst (
	.areset ( ~rst_n ),
	.inclk0 ( clk ),
	.c0 ( clk_50 ), //50M
	.c1 ( clk_25 ) //25M
	);
//根据不同分配率选择不同频率时钟
assign vga_clk = clk_25;


// 行计数
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        cnt_h <= 0;
    end
    else if ( flag_enable_cnt_h ) begin
        if ( flag_clear_cnt_h ) begin
            cnt_h <= 0;
        end
        else begin
            cnt_h <= cnt_h + 1;
        end
    end
    else begin
        cnt_h <= 0;
    end
end
assign flag_enable_cnt_h = 1;
assign flag_clear_cnt_h  = cnt_h == H_TOTAL - 1;

// 行同步信号
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        h_sync <= 0;
    end
    else if ( cnt_h == H_SYNC - 1 ) begin // 同步周期时为1
        h_sync <= 1;
    end
        else if ( flag_clear_cnt_h ) begin // 其余为0
        h_sync <= 0;
        end
    else begin
        h_sync <= h_sync;
    end
end

// 场计数
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        cnt_v <= 0;
    end
    else if ( flag_enable_cnt_v ) begin
        if ( flag_clear_cnt_v ) begin
            cnt_v <= 0;
        end
        else if ( flag_add_cnt_v ) begin
            cnt_v <= cnt_v + 1;
        end
        else begin
            cnt_v <= cnt_v;
        end
    end
    else begin
        cnt_v <= 0;
    end
end
assign flag_enable_cnt_v = flag_enable_cnt_h;
assign flag_clear_cnt_v  = cnt_v == V_TOTAL - 1;
assign flag_add_cnt_v    = flag_clear_cnt_h;

// 场同步信号
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        v_sync <= 0;
    end
    else if ( cnt_v == V_SYNC - 1 ) begin
        v_sync <= 1;
    end
        else if ( flag_clear_cnt_v ) begin
        v_sync <= 0;
        end
    else begin
        v_sync <= v_sync;
    end
end

// 对应有效区域行地址 1-640
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        addr_h <= 0;
    end
    else if ( valid_area ) begin
        addr_h <= cnt_h - H_SYNC - H_BLACK + 1;
    end
    else begin
        addr_h <= 0;
    end
end
// 对应有效区域列地址 1-480
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        addr_v <= 0;
    end
    else if ( valid_area ) begin
        addr_v <= cnt_v -V_SYNC - V_BLACK + 1;
    end
    else begin
        addr_v <= 0;
    end
end
// 有效显示区域
assign valid_area = cnt_h >= H_SYNC + H_BLACK && cnt_h <= H_SYNC + H_BLACK + H_ACT && cnt_v >= V_SYNC + V_BLACK && cnt_v <= V_SYNC + V_BLACK + V_ACT;


// 显示颜色
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        rgb <= 16'h0;
    end
    else if ( valid_area ) begin
        rgb <= rgb_data;
    end
    else begin
        rgb <= 16'b0;
    end
end
assign rgb_r = rgb[ 15:11 ];
assign rgb_g = rgb[ 10:5 ];
assign rgb_b = rgb[ 4:0 ];

endmodule // vga_dirve

• 效果：
  

2、VGA显示字符

• 取字模：
  打开字模选项，选择格式：
  
  注意，这里的学号和名字分开取：
  
  

注意：这里的汉字取的是16x16的点阵，数字取的是32x16的点阵。

• 代码：

module data_drive (input			wire						vga_clk,
                   input			wire						rst_n,
                   input			wire		[ 11:0 ]		addr_h,
                   input			wire		[ 11:0 ]		addr_v,
                   input			wire		[ 2:0 ]		 key,
                   output			reg		[ 15:0 ]				rgb_data);

localparam	red    = 16'd63488;
localparam	orange = 16'd64384;
localparam	yellow = 16'd65472;
localparam	green  = 16'd1024;
localparam	blue   = 16'd31;
localparam	indigo = 16'd18448;
localparam	purple = 16'd32784;
localparam	white  = 16'd65503;
localparam	black  = 16'd0;
reg [ 383:0 ] char_line[ 64:0 ];

localparam	states_1 = 1; // 彩条
localparam	states_2 = 2; // 字符
localparam	states_3 = 3; // 图片

parameter	height = 78; // 图片高度
parameter	width  = 128; // 图片宽度
reg			[ 1:0 ]			states_current			; // 当前状态
reg			[ 1:0 ]			states_next			    ; // 下个状态
reg			[ 13:0 ]		rom_address				; // ROM地址
wire			[ 15:0 ]		rom_data				; // 图片数据

wire							flag_enable_out1			; // 文字有效区域
wire							flag_enable_out2			; // 图片有效区域
wire							flag_clear_rom_address		; // 地址清零
wire							flag_begin_h			    ; // 图片显示行
wire							flag_begin_v			    ; // 图片显示列

//状态转移
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        states_current <= states_1;
    end
    else begin
        states_current <= states_next;
    end
end

//状态判断
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        states_next <= states_1;
    end
    else if ( key[ 0 ] ) begin
        states_next <= states_1;
    end
        else if ( key[ 1 ] ) begin
        states_next <= states_2;
        end
        else if ( key[ 2 ] ) begin
        states_next <= states_3;
        end
    else begin
        states_next <= states_next;
    end
end

//状态输出
always @( * ) begin
    case ( states_current )
        states_1 : begin
            if ( addr_h == 0 ) begin
                rgb_data = black;
            end
            else if ( addr_h >0 && addr_h <81 ) begin
                rgb_data = red;
            end
            else if ( addr_h >80 && addr_h <161 ) begin
                rgb_data = orange;
            end
            else if ( addr_h >160 && addr_h <241 ) begin
                rgb_data = yellow;
            end
            else if ( addr_h >240 && addr_h <321 ) begin
                rgb_data = green;
            end
            else if ( addr_h >320 && addr_h <401 ) begin
                rgb_data = blue;
            end
            else if ( addr_h >400 && addr_h <481 ) begin
                rgb_data = indigo;
            end
            else if ( addr_h >480 && addr_h <561 ) begin
                rgb_data = purple;
            end
            else if ( addr_h >560 && addr_h <641 ) begin
                rgb_data = white;
            end
            else begin
                rgb_data = black;
            end
            
        end
        states_2 : begin
            if ( flag_enable_out1 ) begin
                rgb_data = char_line[ addr_v-208 ][ 532 - addr_h ]? white:black;
            end
            else begin
                rgb_data = black;
            end
        end
        states_3 : begin
            if ( flag_enable_out2 ) begin
                rgb_data = rom_data;
            end
            else begin
                rgb_data = black;
            end
            
        end
        default: begin
            case ( addr_h )
                0 : rgb_data      = black;
                1 : rgb_data      = red;
                81 : rgb_data     = orange;
                161: rgb_data     = yellow;
                241: rgb_data     = green;
                321: rgb_data     = blue;
                401: rgb_data     = indigo;
                481: rgb_data     = purple;
                561: rgb_data     = white;
                default: rgb_data = rgb_data;
            endcase
        end
    endcase
end

assign flag_enable_out1 = states_current == states_2 && addr_h > 148 && addr_h < 533 && addr_v > 208  && addr_v < 273 ;
assign flag_begin_h     = addr_h > ( ( 640 - width ) / 2 ) && addr_h < ( ( 640 - width ) / 2 ) + width + 1;
assign flag_begin_v     = addr_v > ( ( 480 - height )/2 ) && addr_v <( ( 480 - height )/2 ) + height + 1;
assign flag_enable_out2 = states_current == states_3 && flag_begin_h && flag_begin_v;

//ROM地址计数器
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        rom_address <= 0;
    end
    else if ( flag_clear_rom_address ) begin //计数满清零
        rom_address <= 0;
    end
        else if ( flag_enable_out2 ) begin  //在有效区域内+1
        rom_address <= rom_address + 1;
        end
    else begin  //无效区域保持
        rom_address <= rom_address;
    end
end
assign flag_clear_rom_address = rom_address == height * width - 1;

//初始化显示文字
always@( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
       char_line[ 0 ]  = 256'h0000010000000000000000000000000000000000000000000000000000000000;
       char_line[ 1 ]  = 256'h1ff0210020000000000000000000000000000000000000000000000000000000;
       char_line[ 2 ]  = 256'h101011dc17fc0000000000000000000000000000000000000000000000000000;
       char_line[ 3 ]  = 256'h101011141040000018003c003c00180018007e001800180018003c003c000400;
       char_line[ 4 ]  = 256'h1ff0811480400000240042004200240024004200240024002400420042000c00;
       char_line[ 5 ]  = 256'h0000411440400000400042004200420042000400420040004200420042000c00;
       char_line[ 6 ]  = 256'h000047d448400000400002004200420042000400420040004200420042001400;
       char_line[ 7 ]  = 256'h3ff81014084000005c000400020042004200080042005c004200020002002400;
       char_line[ 8 ]  = 256'h0100111410407e00620018000400420042000800420062004200040004002400;
       char_line[ 9 ]  = 256'h0100211410400000420004000800420042001000420042004200080008004400;
       char_line[ 10 ] = 256'hfffee588e0400000420002001000420042001000420042004200100010007f00;
       char_line[ 11 ] = 256'h0280254820400000420042002000420042001000420042004200200020000400;
       char_line[ 12 ] = 256'h0440294820400000220042004200240024001000240022002400420042000400;
       char_line[ 13 ] = 256'h082021142ffe00001c003c007e0018001800100018001c0018007e007e001f00;
       char_line[ 14 ] = 256'h3018251420000000000000000000000000000000000000000000000000000000;
       char_line[ 15 ] = 256'hc006022200000000000000000000000000000000000000000000000000000000;

    end
end

//实例化ROM
rom	rom_inst (
.address ( rom_address ),
.clock ( vga_clk ),
.q ( rom_data )
);
endmodule // data_drive

• 效果：
  

3、输出一幅彩色图像

• 使用软件将图片进行转换：

• 生成的hex文件：

这里没能成功显示

4、Quartus操作

先是新建工程引入.V文件即可，下面是添加两个IP核的操作，一个用于时钟分频，一个用于存储图片。

分别使用640×480 60HZ和800×600 72HZ,对应时钟分别为25M和50M,需要使用PLL进行分频 时钟频率 = 行帧长 × 列帧长 * 刷新率,640 ×480 60HZ对应时钟频率= 800 ×525 × 60 = 25.2M。

1、添加PLL核

• 选择基础时钟：
  
  取消勾选输出使能：
  
• 设置时钟，clk0默认50M即可，c1设为25M.
  
• 勾选下面的选项最后点击finish即可添加pll核
  

2、添加ROM核

• 搜索RO核：
  
• 把宽度设为16位，然后根据图片的大小填写160x154=24640,根据自己的图片来填写。
  
• 取消下面的勾选：
  
• 引入前面生成的hex文件：
  
• 勾选下面选项然后点击finish:
  

三、全部代码

• data_drive文件：

module data_drive (input			wire						vga_clk,
                   input			wire						rst_n,
                   input			wire		[ 11:0 ]		addr_h,
                   input			wire		[ 11:0 ]		addr_v,
                   input			wire		[ 2:0 ]		 key,
                   output			reg		[ 15:0 ]				rgb_data);

localparam	red    = 16'd63488;
localparam	orange = 16'd64384;
localparam	yellow = 16'd65472;
localparam	green  = 16'd1024;
localparam	blue   = 16'd31;
localparam	indigo = 16'd18448;
localparam	purple = 16'd32784;
localparam	white  = 16'd65503;
localparam	black  = 16'd0;
reg [ 383:0 ] char_line[ 64:0 ];

localparam	states_1 = 1; // 彩条
localparam	states_2 = 2; // 字符
localparam	states_3 = 3; // 图片

parameter	height = 78; // 图片高度
parameter	width  = 128; // 图片宽度
reg			[ 1:0 ]			states_current			; // 当前状态
reg			[ 1:0 ]			states_next			    ; // 下个状态
reg			[ 13:0 ]		rom_address				; // ROM地址
wire			[ 15:0 ]		rom_data				; // 图片数据

wire							flag_enable_out1			; // 文字有效区域
wire							flag_enable_out2			; // 图片有效区域
wire							flag_clear_rom_address		; // 地址清零
wire							flag_begin_h			    ; // 图片显示行
wire							flag_begin_v			    ; // 图片显示列

//状态转移
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        states_current <= states_1;
    end
    else begin
        states_current <= states_next;
    end
end

//状态判断
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        states_next <= states_1;
    end
    else if ( key[ 0 ] ) begin
        states_next <= states_1;
    end
        else if ( key[ 1 ] ) begin
        states_next <= states_2;
        end
        else if ( key[ 2 ] ) begin
        states_next <= states_3;
        end
    else begin
        states_next <= states_next;
    end
end

//状态输出
always @( * ) begin
    case ( states_current )
        states_1 : begin
            if ( addr_h == 0 ) begin
                rgb_data = black;
            end
            else if ( addr_h >0 && addr_h <81 ) begin
                rgb_data = red;
            end
            else if ( addr_h >80 && addr_h <161 ) begin
                rgb_data = orange;
            end
            else if ( addr_h >160 && addr_h <241 ) begin
                rgb_data = yellow;
            end
            else if ( addr_h >240 && addr_h <321 ) begin
                rgb_data = green;
            end
            else if ( addr_h >320 && addr_h <401 ) begin
                rgb_data = blue;
            end
            else if ( addr_h >400 && addr_h <481 ) begin
                rgb_data = indigo;
            end
            else if ( addr_h >480 && addr_h <561 ) begin
                rgb_data = purple;
            end
            else if ( addr_h >560 && addr_h <641 ) begin
                rgb_data = white;
            end
            else begin
                rgb_data = black;
            end
            
        end
        states_2 : begin
            if ( flag_enable_out1 ) begin
                rgb_data = char_line[ addr_v-208 ][ 532 - addr_h ]? white:black;
            end
            else begin
                rgb_data = black;
            end
        end
        states_3 : begin
            if ( flag_enable_out2 ) begin
                rgb_data = rom_data;
            end
            else begin
                rgb_data = black;
            end
            
        end
        default: begin
            case ( addr_h )
                0 : rgb_data      = black;
                1 : rgb_data      = red;
                81 : rgb_data     = orange;
                161: rgb_data     = yellow;
                241: rgb_data     = green;
                321: rgb_data     = blue;
                401: rgb_data     = indigo;
                481: rgb_data     = purple;
                561: rgb_data     = white;
                default: rgb_data = rgb_data;
            endcase
        end
    endcase
end

assign flag_enable_out1 = states_current == states_2 && addr_h > 148 && addr_h < 533 && addr_v > 208  && addr_v < 273 ;
assign flag_begin_h     = addr_h > ( ( 640 - width ) / 2 ) && addr_h < ( ( 640 - width ) / 2 ) + width + 1;
assign flag_begin_v     = addr_v > ( ( 480 - height )/2 ) && addr_v <( ( 480 - height )/2 ) + height + 1;
assign flag_enable_out2 = states_current == states_3 && flag_begin_h && flag_begin_v;

//ROM地址计数器
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        rom_address <= 0;
    end
    else if ( flag_clear_rom_address ) begin //计数满清零
        rom_address <= 0;
    end
        else if ( flag_enable_out2 ) begin  //在有效区域内+1
        rom_address <= rom_address + 1;
        end
    else begin  //无效区域保持
        rom_address <= rom_address;
    end
end
assign flag_clear_rom_address = rom_address == height * width - 1;

//初始化显示文字
always@( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
       char_line[ 0 ]  = 256'h0000010000000000000000000000000000000000000000000000000000000000;
       char_line[ 1 ]  = 256'h1ff0210020000000000000000000000000000000000000000000000000000000;
       char_line[ 2 ]  = 256'h101011dc17fc0000000000000000000000000000000000000000000000000000;
       char_line[ 3 ]  = 256'h101011141040000018003c003c00180018007e001800180018003c003c000400;
       char_line[ 4 ]  = 256'h1ff0811480400000240042004200240024004200240024002400420042000c00;
       char_line[ 5 ]  = 256'h0000411440400000400042004200420042000400420040004200420042000c00;
       char_line[ 6 ]  = 256'h000047d448400000400002004200420042000400420040004200420042001400;
       char_line[ 7 ]  = 256'h3ff81014084000005c000400020042004200080042005c004200020002002400;
       char_line[ 8 ]  = 256'h0100111410407e00620018000400420042000800420062004200040004002400;
       char_line[ 9 ]  = 256'h0100211410400000420004000800420042001000420042004200080008004400;
       char_line[ 10 ] = 256'hfffee588e0400000420002001000420042001000420042004200100010007f00;
       char_line[ 11 ] = 256'h0280254820400000420042002000420042001000420042004200200020000400;
       char_line[ 12 ] = 256'h0440294820400000220042004200240024001000240022002400420042000400;
       char_line[ 13 ] = 256'h082021142ffe00001c003c007e0018001800100018001c0018007e007e001f00;
       char_line[ 14 ] = 256'h3018251420000000000000000000000000000000000000000000000000000000;
       char_line[ 15 ] = 256'hc006022200000000000000000000000000000000000000000000000000000000;

    end
end

//实例化ROM
rom	rom_inst (
.address ( rom_address ),
.clock ( vga_clk ),
.q ( rom_data )
);
endmodule // data_drive

• key_debounce文件：

module key_debounce(
	input 	wire	clk,
	input 	wire 	rst_n,
	input 	wire 	key,
	
	output 	reg 	flag,// 0抖动, 1抖动结束
	output 	reg	key_value//key抖动结束后的值
);

parameter MAX_NUM = 20'd1_000_000;

reg [19:0] delay_cnt;//1_000_000

reg key_reg;//key上一次的值

always @(posedge clk or negedge rst_n) begin
	if(!rst_n) begin
		key_reg <= 1;
		delay_cnt <= 0;
	end
	
	else begin
		key_reg <= key;
		//当key为1 key 为0 表示按下抖动,开始计时
		if(key_reg  != key  ) begin 
		   delay_cnt <= MAX_NUM ;
		end
		else begin
		    if(delay_cnt > 0)
				delay_cnt <= delay_cnt -1;
			else
				delay_cnt <= 0;
		end
	end
end


//当计时完成,获取key的值
always @(posedge clk or negedge rst_n) begin
	if(!rst_n) begin
		flag <= 0;
		key_value <= 1;
	end

	else begin
		
		// 计时完成 处于稳定状态,进行赋值
		if(delay_cnt == 1) begin
			flag <= 1;
			key_value <= key;
		end
		else begin
			flag <= 0;
			key_value <= key_value;
		end
	end
end

endmodule

• vga_dirve文件：

module vga_dirve (input			wire						clk,            //系统时钟
                  input			wire						rst_n,          //复位
                  input			wire		[ 15:0 ]		rgb_data,       //16位RGB对应值
                  output			wire							vga_clk,    //vga时钟 25M
                  output			reg							h_sync,     //行同步信号
                  output			reg							v_sync,     //场同步信号
                  output			reg		[ 11:0 ]				addr_h, //行地址
                  output			reg		[ 11:0 ]				addr_v,  //列地址
                  output			wire		[ 4:0 ]				rgb_r,  //红基色
                  output			wire		[ 5:0 ]				rgb_g,  //绿基色
                  output			wire		[ 4:0 ]				rgb_b  //蓝基色
);

// 640 * 480 60HZ
localparam	 H_FRONT = 16; // 行同步前沿信号周期长
localparam	 H_SYNC  = 96; // 行同步信号周期长
localparam	 H_BLACK = 48; // 行同步后沿信号周期长
localparam	 H_ACT   = 640; // 行显示周期长
localparam	 V_FRONT = 11; // 场同步前沿信号周期长
localparam	 V_SYNC  = 2; // 场同步信号周期长
localparam	 V_BLACK = 31; // 场同步后沿信号周期长
localparam	 V_ACT   = 480; // 场显示周期长

// 800 * 600 72HZ
// localparam	 H_FRONT = 40; // 行同步前沿信号周期长
// localparam	 H_SYNC  = 120; // 行同步信号周期长
// localparam	 H_BLACK = 88; // 行同步后沿信号周期长
// localparam	 H_ACT   = 800; // 行显示周期长
// localparam	 V_FRONT = 37; // 场同步前沿信号周期长
// localparam	 V_SYNC  = 6; // 场同步信号周期长
// localparam	 V_BLACK = 23; // 场同步后沿信号周期长
// localparam	 V_ACT   = 600; // 场显示周期长


localparam	H_TOTAL = H_FRONT + H_SYNC + H_BLACK + H_ACT; // 行周期
localparam	V_TOTAL = V_FRONT + V_SYNC + V_BLACK + V_ACT; // 列周期

reg			[ 11:0 ]			cnt_h			; // 行计数器
reg			[ 11:0 ]			cnt_v			; // 场计数器
reg			[ 15:0 ]			rgb			; // 对应显示颜色值

// 对应计数器开始、结束、计数信号
wire							flag_enable_cnt_h			;
wire							flag_clear_cnt_h			;
wire							flag_enable_cnt_v			;
wire							flag_clear_cnt_v			;
wire							flag_add_cnt_v  			;
wire							valid_area      			;


// 25M时钟 行周期*场周期*刷新率 = 800 * 525* 60
wire							clk_25			;
// 50M时钟 1040 * 666 * 72
wire							clk_50			;
//PLL
pll	pll_inst (
	.areset ( ~rst_n ),
	.inclk0 ( clk ),
	.c0 ( clk_50 ), //50M
	.c1 ( clk_25 ) //25M
	);
//根据不同分配率选择不同频率时钟
assign vga_clk = clk_25;


// 行计数
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        cnt_h <= 0;
    end
    else if ( flag_enable_cnt_h ) begin
        if ( flag_clear_cnt_h ) begin
            cnt_h <= 0;
        end
        else begin
            cnt_h <= cnt_h + 1;
        end
    end
    else begin
        cnt_h <= 0;
    end
end
assign flag_enable_cnt_h = 1;
assign flag_clear_cnt_h  = cnt_h == H_TOTAL - 1;

// 行同步信号
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        h_sync <= 0;
    end
    else if ( cnt_h == H_SYNC - 1 ) begin // 同步周期时为1
        h_sync <= 1;
    end
        else if ( flag_clear_cnt_h ) begin // 其余为0
        h_sync <= 0;
        end
    else begin
        h_sync <= h_sync;
    end
end

// 场计数
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        cnt_v <= 0;
    end
    else if ( flag_enable_cnt_v ) begin
        if ( flag_clear_cnt_v ) begin
            cnt_v <= 0;
        end
        else if ( flag_add_cnt_v ) begin
            cnt_v <= cnt_v + 1;
        end
        else begin
            cnt_v <= cnt_v;
        end
    end
    else begin
        cnt_v <= 0;
    end
end
assign flag_enable_cnt_v = flag_enable_cnt_h;
assign flag_clear_cnt_v  = cnt_v == V_TOTAL - 1;
assign flag_add_cnt_v    = flag_clear_cnt_h;

// 场同步信号
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        v_sync <= 0;
    end
    else if ( cnt_v == V_SYNC - 1 ) begin
        v_sync <= 1;
    end
        else if ( flag_clear_cnt_v ) begin
        v_sync <= 0;
        end
    else begin
        v_sync <= v_sync;
    end
end

// 对应有效区域行地址 1-640
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        addr_h <= 0;
    end
    else if ( valid_area ) begin
        addr_h <= cnt_h - H_SYNC - H_BLACK + 1;
    end
    else begin
        addr_h <= 0;
    end
end
// 对应有效区域列地址 1-480
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        addr_v <= 0;
    end
    else if ( valid_area ) begin
        addr_v <= cnt_v -V_SYNC - V_BLACK + 1;
    end
    else begin
        addr_v <= 0;
    end
end
// 有效显示区域
assign valid_area = cnt_h >= H_SYNC + H_BLACK && cnt_h <= H_SYNC + H_BLACK + H_ACT && cnt_v >= V_SYNC + V_BLACK && cnt_v <= V_SYNC + V_BLACK + V_ACT;


// 显示颜色
always @( posedge vga_clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        rgb <= 16'h0;
    end
    else if ( valid_area ) begin
        rgb <= rgb_data;
    end
    else begin
        rgb <= 16'b0;
    end
end
assign rgb_r = rgb[ 15:11 ];
assign rgb_g = rgb[ 10:5 ];
assign rgb_b = rgb[ 4:0 ];

endmodule // vga_dirve

• vga_top顶层文件：

module vga_top (input			wire						clk,
                input			wire						rst_n,
                input			wire		[ 2:0 ]		    key,
                output			wire						vga_clk,
                output			wire						h_sync,
                output			wire						v_sync,
                output			wire		[ 4:0 ]			rgb_r,
                output			wire		[ 5:0 ]			rgb_g,
                output			wire		[ 4:0 ]			rgb_b,
                output			reg		    [ 3:0 ]			led);

reg			[ 27:0 ]			cnt			        ;
wire		[ 11:0 ]		    addr_h              ;
wire		[ 11:0 ]		    addr_v              ;
wire		[ 15:0 ]			rgb_data			;
wire		[ 2:0 ]			    key_flag			;
wire		[ 2:0 ]			    key_value			;

//vga模块
vga_dirve u_vga_dirve(
.clk      ( clk ),
.rst_n    ( rst_n ),
.rgb_data ( rgb_data ),
.vga_clk  ( vga_clk ),
.h_sync   ( h_sync ),
.v_sync   ( v_sync ),
.rgb_r    ( rgb_r ),
.rgb_g    ( rgb_g ),
.rgb_b    ( rgb_b ),
.addr_h   ( addr_h ),
.addr_v   ( addr_v )
);

//数据模块
data_drive u_data_drive(
.vga_clk ( vga_clk ),
.rst_n   ( rst_n ),
.addr_h  ( addr_h ),
.addr_v  ( addr_v ),
.key     ( {
    
    key_value[ 2 ] && key_flag[ 2 ], key_value[ 1 ] && key_flag[ 1 ], key_value[ 0 ] && key_flag[ 0 ] } ),
.rgb_data  ( rgb_data )
);


//按键消抖
key_debounce u_key_debounce0(
.clk   ( vga_clk ),
.rst_n ( rst_n ),
.key   ( key[ 0 ] ),
.flag  ( key_flag[ 0 ] ),
.key_value  ( key_value[ 0 ] )
);

key_debounce u_key_debounce1(
.clk   ( vga_clk ),
.rst_n ( rst_n ),
.key   ( key[ 1 ] ),
.flag  ( key_flag[ 1 ] ),
.key_value  ( key_value[ 1 ] )
);

key_debounce u_key_debounce2(
.clk   ( vga_clk ),
.rst_n ( rst_n ),
.key   ( key[ 2 ] ),
.flag  ( key_flag[ 2 ] ),
.key_value  ( key_value[ 2 ] )
);

// led
always @( posedge clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        cnt <= 0;
    end
    else if ( cnt == 50_000_000 - 1 ) begin
        cnt <= 0;
    end
    else begin
        cnt <= cnt + 1;
    end
end
always @( posedge clk or negedge rst_n ) begin
    if ( !rst_n ) begin
        led <= 4'b0000;
    end
    else if ( cnt == 50_000_000 -1 )begin
        led <= ~led;
    end
    else begin
        led <= led;
    end
end
endmodule // vga_top

---

四、总结

了解了VGA显示的原理，其实就是为每个坐标分配一个RGB三通道的值，就是每个像素，场信号扫描得很快就能连成一幅图像。掌握了两种IP核的使用，就是图片没能成功显示。

五、参考资料

https://blog.csdn.net/qq_45659777/article/details/124834294
https://blog.csdn.net/qq_47281915/article/details/125134764