GNU Radio: 自定义 block 实例

综述

本文通过在GNU Radio 中编写一个block的例子，系统介绍创建一个block的过程。该 block 的功能是可以在GRC中通过滑块(WX GUI Slider)来实时改变信号源(Signal Source)的相位偏移。

步骤详解

1. 使用 gr_modtool 工具创建 block 的框架，GNU Radio 会自动帮我们创建所需要的文件及文件夹。

$ gr_modtool newmod myblk
Creating out-of-tree module in ./gr-myblk... Done.
Use 'gr_modtool add' to add a new block to this currently empty module.
$ cd gr-myblk
/gr-myblk$ ls
apps  cmake  CMakeLists.txt  docs  examples  grc  include  lib  python  swig

2. 使用Git版本控制(可选)

在gr-myblock文件夹下执行以下命令，创建一个Git仓库，可用于版本控制。git常用命令速查点这里。

/gr-myblk$ git init

3. 添加block

执行以下命令添加block。参数类型为double，因为我们要传递的角度是0~360度double类型，不填默认没有参数，但后期可以自己添加。根据是否需要Python或者C++测试代码选择Y或者n，如果不填默认为Y。

/gr-myblk$ gr_modtool add -t sync phase_offset
GNU Radio module name identified: myblk
Language: C++
Block/code identifier: phase_offset
Enter valid argument list, including default arguments: double angle
Add Python QA code? [Y/n] n
Add C++ QA code? [Y/n] n
Adding file 'lib/phase_offset_impl.h'...
Adding file 'lib/phase_offset_impl.cc'...
Adding file 'include/myblk/phase_offset.h'...
Editing swig/myblk_swig.i...
Adding file 'grc/myblk_phase_offset.xml'...
Editing grc/CMakeLists.txt...

4. 编辑代码

从上一条命令的输出可以看出，gr_modtood已经为我们自动创建了4个文件，分别是:

• lib/phase_offset_impl.h
• lib/phase_offset_impl.cc
• include/myblk/phase_offset.h
• grc/myblk_phase_offset.xml

分别修改这4个文件如下：

1 /* -*- c++ -*- */
 2 /* 
 3  * Copyright 2016 <+YOU OR YOUR COMPANY+>.
 4  * 
 5  * This is free software; you can redistribute it and/or modify
 6  * it under the terms of the GNU General Public License as published by
 7  * the Free Software Foundation; either version 3, or (at your option)
 8  * any later version.
 9  * 
10  * This software is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  * 
15  * You should have received a copy of the GNU General Public License
16  * along with this software; see the file COPYING.  If not, write to
17  * the Free Software Foundation, Inc., 51 Franklin Street,
18  * Boston, MA 02110-1301, USA.
19  */
20 
21 #ifdef HAVE_CONFIG_H
22 #include "config.h"
23 #endif
24 
25 #include <gnuradio/io_signature.h>
26 #include "phase_offset_impl.h"
27 
28 namespace gr {
29   namespace myblk {
30 
31     phase_offset::sptr
32     phase_offset::make(double angle)
33     {
34       return gnuradio::get_initial_sptr
35         (new phase_offset_impl(angle));
36     }
37 
38     /*
39      * The private constructor
40      */
41     phase_offset_impl::phase_offset_impl(double angle)
42       : gr::sync_block("phase_offset",
43               gr::io_signature::make(1, 1, sizeof(gr_complex)),
44               gr::io_signature::make(1, 1, sizeof(gr_complex)))
45       , d_offset_angle(angle)
46     {}
47 
48     /*
49      * Our virtual destructor.
50      */
51     phase_offset_impl::~phase_offset_impl()
52     {
53     }
54 
55     int
56     phase_offset_impl::work(int noutput_items,
57               gr_vector_const_void_star &input_items,
58               gr_vector_void_star &output_items)
59     {
60         const gr_complex *in = (const gr_complex *) input_items[0];
61         gr_complex *out = (gr_complex *) output_items[0];
62 
63         double rad = d_offset_angle/180*PI;//将角度变成弧度
64         // Do <+signal processing+>
65         for (int i = 0; i < noutput_items; ++i)
66         {
67           out[i] = in[i] * gr_complex(cos(rad), sin(rad));
68         }
69 
70         std::cout << "d_offset_angle = " << d_offset_angle << std::endl;
71 
72         // Tell runtime system how many output items we produced.
73         return noutput_items;
74     }
75 
76   } /* namespace myblk */
77 } /* namespace gr */

View Code phase_offset_impl.cc

1 /* -*- c++ -*- */
 2 /* 
 3  * Copyright 2016 <+YOU OR YOUR COMPANY+>.
 4  * 
 5  * This is free software; you can redistribute it and/or modify
 6  * it under the terms of the GNU General Public License as published by
 7  * the Free Software Foundation; either version 3, or (at your option)
 8  * any later version.
 9  * 
10  * This software is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  * 
15  * You should have received a copy of the GNU General Public License
16  * along with this software; see the file COPYING.  If not, write to
17  * the Free Software Foundation, Inc., 51 Franklin Street,
18  * Boston, MA 02110-1301, USA.
19  */
20 
21 #ifndef INCLUDED_MYBLK_PHASE_OFFSET_IMPL_H
22 #define INCLUDED_MYBLK_PHASE_OFFSET_IMPL_H
23 
24 #include <myblk/phase_offset.h>
25 
26 namespace gr {
27   namespace myblk {
28 
29     class phase_offset_impl : public phase_offset
30     {
31      private:
32       double d_offset_angle;
33 
34      public:
35       phase_offset_impl(double angle);
36       ~phase_offset_impl();
37 
38       void set_angle_offset(double angle)
39       {
40         d_offset_angle = angle;
41       }
42 
43       // Where all the action really happens
44       int work(int noutput_items,
45            gr_vector_const_void_star &input_items,
46            gr_vector_void_star &output_items);
47     };
48 
49   } // namespace myblk
50 } // namespace gr
51 
52 #endif /* INCLUDED_MYBLK_PHASE_OFFSET_IMPL_H */

View Code phase_offset_impl.h

1 /* -*- c++ -*- */
 2 /* 
 3  * Copyright 2016 <+YOU OR YOUR COMPANY+>.
 4  * 
 5  * This is free software; you can redistribute it and/or modify
 6  * it under the terms of the GNU General Public License as published by
 7  * the Free Software Foundation; either version 3, or (at your option)
 8  * any later version.
 9  * 
10  * This software is distributed in the hope that it will be useful,
11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13  * GNU General Public License for more details.
14  * 
15  * You should have received a copy of the GNU General Public License
16  * along with this software; see the file COPYING.  If not, write to
17  * the Free Software Foundation, Inc., 51 Franklin Street,
18  * Boston, MA 02110-1301, USA.
19  */
20 
21 
22 #ifndef INCLUDED_MYBLK_PHASE_OFFSET_H
23 #define INCLUDED_MYBLK_PHASE_OFFSET_H
24 
25 #include <myblk/api.h>
26 #include <gnuradio/sync_block.h>
27 
28 #define PI 3.14159265358979323846
29 
30 namespace gr {
31   namespace myblk {
32 
33     /*!
34      * brief <+description of block+>
35      * ingroup myblk
36      *
37      */
38     class MYBLK_API phase_offset : virtual public gr::sync_block
39     {
40      public:
41       typedef boost::shared_ptr<phase_offset> sptr;
42 
43       /*!
44        * brief Return a shared_ptr to a new instance of myblk::phase_offset.
45        *
46        * To avoid accidental use of raw pointers, myblk::phase_offset's
47        * constructor is in a private implementation
48        * class. myblk::phase_offset::make is the public interface for
49        * creating new instances.
50        */
51       static sptr make(double angle);
52       virtual void set_angle_offset(double angle) = 0;
53     };
54 
55   } // namespace myblk
56 } // namespace gr
57 
58 #endif /* INCLUDED_MYBLK_PHASE_OFFSET_H */

View Code phase_offset.h

1 <block>
 2   <name>Phase offset</name>
 3   <key>myblk_phase_offset</key>
 4   <category>MYBLK</category>
 5   <import>import myblk</import>
 6   <make>myblk.phase_offset($angle)</make>
 7   <callback>set_angle_offset($angle)</callback>
 8   <param>
 9     <name>Angle</name>
10     <key>angle</key>
11     <value>0</value>
12     <type>real</type>
13   </param>
14   <sink>
15     <name>in</name>
16     <type>complex</type>
17   </sink>
18   <source>
19     <name>out</name>
20     <type>complex</type>
21   </source>
22 </block>

View Code myblk_phase_offset.xml
5. 编译

依次执行下面的命令完成编译工作

/gr-myblk$ mkdir build
/gr-myblk$ cd build
/gr-myblk/build$ cmake ../
/gr-myblk/build$ make
/gr-myblk/build$ sudo make install
/gr-myblk/build$ sudo ldconfig

注意：如果出现类似错误提示AttributeError:'module'objecthas no attribute'xxxx'， 运行sudoldconfig即可解决.

6. 在GRC中测试验证

流图与运行结果如下：

注意事项

一般我们在block设置的参数，只有在C++类的构造函数中初始化一次赋值。也就是说我们设置的参数只能在程序运行的一开始将参数传递到C++中。但是如果要想像上面的 block 那样在程序运行过程中实时改变参数的值，就需要在xml文件中调用<callback>...callback>关键字，调用C++的成员函数，修改成员变量的值。如本程序中xml中的语句：<callback>set_angle_offset($angle)callback>

对应C++中函数如下：

1 void set_angle_offset(double angle)
2 {
3   d_offset_angle = angle;
4 }

除此之外，还要注意参数类型匹配。WX GUI Slider传递的参数类型为real，因此angle的数据类型也应该为real，如果设置为int则会报错，grc不会像C++一样支持数据类型隐式转换，因此要注意类型匹配。

Slider中输入的是角度，C++运算时需要将角度转化成弧度来计算。
原文链接: https://www.cnblogs.com/moon1992/p/5787164.html

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