轻量化Verilog学习环境搭建

本文记录基于vscode、iverilog搭建轻量化Verilog学习环境的方法。
ref: VSCode Verilog工具链、linux下搭建轻量易用的verilog仿真环境

环境搭建

（1）安装iverilog，这是一个轻量化的开源verilog编译器，配合gtkwave可进行波形仿真。

sudo apt-get install iverilog
sudo apt-get install gtkwave

（2）安装vscode插件Verilog-HDL为verilog提供语法高亮和静态检查等基本支持。打开扩展设置，设置Verilog格式化插件和Lint插件。其中Lint插件可选iVerilog。Format插件可选Verible( 下载地址)。将Verible二进制文件解压到/usr/local/bin，并在插件设置中填好二进制文件的路径。

（3）添加一个简单的自动化脚本来自动调用iverilog，提高效率。

工程结构（下载）：

verilog_learn/
├── build
│   ├── a.out
│   ├── wave.vcd
├── gtkwave.tcl
├── led_demo_tb.v
├── led_demo.v
├── run.sh
└── .vscode
    └── tasks.json

run.sh：

echo "Handling: $1..." # the verilog file
source="../$1.v"
testbanch="../$1_tb.v"

# 生成波形文件
iverilog -o ./a.out $source $testbanch
vvp -n ./a.out -lxt2

# 使用gtkwave查看仿真波形
# https://blog.csdn.net/yelllowcong/article/details/78424329
isGtkWaveRunning=$(ps -ef |grep gtkwave |grep -v "grep" |wc -l)
if [ $isGtkWaveRunning -eq 0 ]; then
        # echo NOT RUN
        gtkwave wave.vcd --script=../gtkwave.tcl
else
        # echo is RUN
        echo "gtkwave is running"
        # gtkwave wave.vcd
fi
# 综合并可视化网表
# yosys -p 'prep ; show -format pdf -prefix yosys' $source
# code ./yosys.pdf

其中gtkwave.tcl文件是对gtkwave进行自动化配置的脚本，内容如下：

# ref: https://gist.github.com/davidzwa/ef1eafc6cd23e613af612e27eddb054b
# ref: https://ughe.github.io/2018/11/13/gtkwave-automation
# Add all signals
set nfacs [ gtkwave::getNumFacs ]
set all_facs [list]
for {set i 0} {$i < $nfacs } {incr i} {
    set facname [ gtkwave::getFacName $i ]
    lappend all_facs "$facname"
}
set num_added [ gtkwave::addSignalsFromList $all_facs ]
puts "num signals added: $num_added"

# zoom full
gtkwave::/Time/Zoom/Zoom_Full

随后在vscode中新建一个task（存于.vscode/task.json路径）来自动运行run.sh，这样在xxx.v文件下按快捷键ctrl+shift+B即可执行run.sh。

{
    // See https://go.microsoft.com/fwlink/?LinkId=733558
    // for the documentation about the tasks.json format
    "version": "2.0.0",
    "options": {
        // 这里指定tasks 的运行目录，默认是${workspaceRoot}，也就是.vscode/..
        "cwd": "${workspaceRoot}/build"
    },
    "tasks": [
        {
            // 这个task完成编译
            "label": "build",
            "type": "shell",
            "command": "../run.sh",
            "args": [
                "${fileBasenameNoExtension}"
            ]
        },
    ]
}

验证

添加led_demo.v及其测试脚本led_demo_tb.v
led_demo.v:

module led_demo(
        input clk,
        input rst_n,

        output reg led
);

reg [7:0] cnt;

always @ (posedge clk)
begin
        if(!rst_n)
                cnt <= 0;
        else if(cnt >= 10)
                cnt <= 0;
        else
                cnt <= cnt + 1;
end

always @ (posedge clk)
begin
        if(!rst_n)
                led <= 0;
        else if(cnt == 10)
                led <= !led;
end

endmodule

led_demo_tb.v

`timescale 1ns/100ps

module led_demo_tb;

parameter SYSCLK_PERIOD = 10;

reg SYSCLK;
reg NSYSRESET;

initial
begin
    SYSCLK = 1'b0;
    NSYSRESET = 1'b0;
end

/*iverilog */
initial
begin
    $dumpfile("wave.vcd");        //生成的vcd文件名称
    $dumpvars(0, led_demo_tb);    //tb模块名称
end
/*iverilog */

initial
begin
    #(SYSCLK_PERIOD * 10 )
        NSYSRESET = 1'b1;
        #1000
                $stop;
end

always @(SYSCLK)
    #(SYSCLK_PERIOD / 2.0) SYSCLK <= !SYSCLK;

led_demo led_demo_ut0 (
    // Inputs
    .rst_n(NSYSRESET),
    .clk(SYSCLK),

    // Outputs
    .led( led)
);

endmodule

打开led_demo.v，按快捷键ctrl+shift+B，即可自动执行编译，并开启gtkwave显示仿真波形：