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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。
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:
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 // Do <+signal processing+> 64 for (int i = 0; i < noutput_items; ++i) 65 { 66 out[i] = in[i] * gr_complex(sin(d_offset_angle), cos(d_offset_angle)); 67 } 68 69 std::cout << "d_offset_angle = " << d_offset_angle << std::endl; 70 71 // Tell runtime system how many output items we produced. 72 return noutput_items; 73 } 74 75 } /* namespace myblk */ 76 } /* namespace gr */
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 */
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 namespace gr { 29 namespace myblk { 30 31 /*! 32 * \brief <+description of block+> 33 * \ingroup myblk 34 * 35 */ 36 class MYBLK_API phase_offset : virtual public gr::sync_block 37 { 38 public: 39 typedef boost::shared_ptr<phase_offset> sptr; 40 41 /*! 42 * \brief Return a shared_ptr to a new instance of myblk::phase_offset. 43 * 44 * To avoid accidental use of raw pointers, myblk::phase_offset‘s 45 * constructor is in a private implementation 46 * class. myblk::phase_offset::make is the public interface for 47 * creating new instances. 48 */ 49 static sptr make(double angle); 50 virtual void set_angle_offset(double angle) = 0; 51 }; 52 53 } // namespace myblk 54 } // namespace gr 55 56 #endif /* INCLUDED_MYBLK_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>
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
6. 在GRC中测试验证
流图与运行结果如下：
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。
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原文地址：http://www.cnblogs.com/moon1992/p/5787164.html
