UHD C/C++ 编程实例 USRP发送、接收数据

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UHD C/C++ 编程实例 USRP发送、接收数据

原始博客内容http://blog.csdn.net/jxwxg/article/details/53142911

1. UHD库函数简介1.1 发送函数

新建一个usrp设备

1. std::string args = " "; args指定USRP地址，配置USRP参数等
   
2. uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(args);

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设置时钟源和时钟频率

1. std::string ref = "internal"; // internal,external, MIMO.
   
2. usrp->set_clock_source(ref);
   
3. double rate = 40e6;
   
4. usrp->set_master_clock_rate(rate);
   
5. usrp->get_clock_source() //获取当前的时钟源
   
6. usrp->get_clock_sources() //获取所有可用的时钟源
   
7. usrp->get_master_clock_rate(); //获取时钟频率

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设置采样率

1. double samp_rate = 20e6;
   
2. usrp->set_tx_rate(samp_rate);
   
3. usrp->get_tx_rate() //获取当前的采样率
   
4. usrp->get_tx_rates() //获取采样率的采样范围

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设置发射中心频点

1. double freq = 2.412e9;
   
2. usrp->set_tx_freq(freq);
   
3. usrp->get_fe_tx_freq_range();
   
4. usrp->get_tx_freq();
   
5. usrp->get_tx__freq_range();

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设置发射增益

1. double tx_gain = 60;
   
2. usrp->set_tx_gain(tx_gain);

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设置发射天线

默认情况下无需设置发射天线，如需指定特定发射天线时设置。

1. usrp->set_tx_antenna(0);
   
2. usrp->get_tx_antenna();
   
3. usrp->get_tx_antennas();

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创建发送流

新建发送流参数

1. std::string cpu_format = "fc32";
   
2. 目前cpu_format支持的类型有：fc64 - complex fc32 - complex sc16 - complex sc8 - complex
   
3. std::string wire_format = "sc16";
   
4. 目前wire_format支持的类型有：sc16 - Q16 I16 sc8 - Q8_1 I8_1 Q8_0 I8_0
   
5. uhd::stream_args_t stream_args(cpu_format,wire_format);
   
6. uhd::tx_streamer::sptr tx_stream =usrp->get_tx_stream(stream_args);

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中频数据管理

1. uhd::tx_metada_t md; //结构体描述接收到的中频信号
   
2. md.start_of_burst = false; // 设置为真的时候发送第一个数据包
   
3. md.end_of_burst = false; // 设置为真的时候发送最后一个数据包
   
4. md.has_time_spec = false; // 设置为false时立即发送，设置为真的时候在特定时间发送

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1.2 接收函数

创建一个usrp

1. std::string args = " ";
   
2. uhd::usrp::multi_usrp::sptr usrp =uhd::usrp::multi_usrp::make(args);

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设置时钟源和时钟频率

1. std::string ref = "internal"; //internal,external and MIMO
   
2. usrp->set_clock_source(ref);
   
3. double clock_rate = 40e6;
   
4. usrp->set_master_clock_rate(clock_rate);

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设置采样率

1. double rate = 20e6;
   
2. usrp->set_rx_rate(rate);

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设置中心频率

1. double freq = 2.412e9;
   
2. usrp->set_rx_freq(freq);

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设置增益

1. double rx_gain = 50;
   
2. usrp->set_rx_gain(rx_gain);

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创建接收流

1. std::string cpu_format = "fc32";
   
2. std::string wire_format = "sc16";
   
3. uhd::stream_args_t stream_args(cpu_format,wire_format);
   
4. uhd::rx_streamer::sptr rx_stream =usrp->get_rx_stream(stream_args);

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设置接收模式

1. uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
   
2. //UHD_STREAM_MODE_START_CONTINUOUS=97,//UHD_STREAM_MODE_STOP_CONTINUOUS=111,//UHD_STREAM_MODE_NUM_SAMPS_AND_DONE=100,//UHD_STREAM_MODE_NUM_SAMPS_AND_MORE=109
   
3. stream_cmd.num_samps = 1000; // 接收采样点数
   
4. stream_cmd.stream_now = true; //现在开始接收
   
5. rx_stream->issue_stream_cmd(stream_cmd); //配置rx_stream参数

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2. USRP发送数据

　　代码实现USRP发送二进制文件802.11a_BUPT41.seg内的数据。里面的数据为float complex类型，复数的实部和虚部交替存储。即如下图所示。用户可以把要发送的数据生成对应的二进制文件，也可以直接写成数组放在代码中。注意：float类型数据的单位1就是 “1”。

这里写图片描述

源码

1. #include <uhd/usrp/multi_usrp.hpp>
   
2. #include <signal.h>
   
3. #define SAMPLE_PER_BUFF 2000
   
4. int stop_signal_called = 0;
   
5. void sig_int_handle(int)
   
6. {
   
7. stop_signal_called = 1;
   
8. printf("stop tx.........\n");
   
9. exit(0);
   
10. }
    
11. int main()
    
12. {
    
13. std::string addr_args = " ";
    
14. uhd::usrp::multi_usrp::sptr usrp =uhd::usrp::multi_usrp::make(addr_args);
    
15. printf("Create a usrp......\n");
    
16. // set the ref and clock rate
    
17. std::string ref = "internal";
    
18. usrp->set_clock_source(ref);
    
19. float clock_rate = 40e6;
    
20. usrp->set_master_clock_rate(clock_rate);
    
21. printf("set the clock rate %0.2f \n",usrp->get_master_clock_rate() );
    
22. // set the sample rate
    
23. float samp_rate = 20e6;
    
24. usrp->set_tx_rate(samp_rate);
    
25. printf("set the tx sample rate to %0.2f \n",usrp->get_tx_rate());
    
26. // set the center frequency
    
27. float center_freq = 2.412e9;
    
28. usrp->set_tx_freq(center_freq);
    
29. printf("set the tx center freq to %0.2f \n",usrp->get_tx_freq());
    
30. // set the rf gain
    
31. float tx_gain = 90;
    
32. usrp->set_tx_gain(tx_gain);
    
33. printf("set the tx gain to %0.2f \n",usrp->get_tx_gain());
    
34. // create a tx stream
    
35. std::string cpu_format = "fc32";
    
36. std::string wire_format = "sc16";
    
37. uhd::stream_args_t stream_args(cpu_format,wire_format);
    
38. uhd::tx_streamer::sptr tx_stream =usrp->get_tx_stream(stream_args);
    
39. uhd::tx_metadata_t md;
    
40. // catch the INT signal
    
41. signal(SIGINT, sig_int_handle);
    
42. float read_buff[SAMPLE_PER_BUFF * 2] = {0};
    
43. while(!stop_signal_called)
    
44. {
    
45. FILE *fp = fopen("802.11a_BUPT41.seg","rb");
    
46. md.start_of_burst = false;
    
47. md.end_of_burst = false;
    
48. while( (!md.end_of_burst) && (!stop_signal_called))
    
49. {
    
50. int read_length = 0;
    
51. if( (read_length = fread(read_buff, sizeof(uint32_t),SAMPLE_PER_BUFF * 2, fp) ) == (SAMPLE_PER_BUFF * 2) )
    
52. {
    
53. //int index;
    
54. //for(index = 0; index < SAMPLE_PER_BUFF * 2;index++)
    
55. // printf("%0.2f ", read_buff[index]);
    
56. //puts("");
    
57. //md.start_of_burst = true;
    
58. tx_stream->send(read_buff, SAMPLE_PER_BUFF, md);
    
59. //md.start_of_burst = false;
    
60. //sleep(1);
    
61. }
    
62. else if(read_length >= 0)
    
63. {
    
64. md.end_of_burst = true;
    
65. }
    
66. }
    
67. fclose(fp);
    
68. }
    
69. return 0;
    
70. }

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编译

g++ 编译时需要链接uhd库，系统需提前安装UHD驱动。具体过程参见之前博客。Ubuntu14.04 源码安装 UHD3.8.0

1. g++ tx.cpp -o tx -luhd

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3. USRP接收数据

　　启动USRP，并使USRP一直接收数据。

源码

1. #include <uhd/usrp/multi_usrp.hpp>
   
2. #include <csignal>
   
3. #define SAMPLE_PER_BUFF 2000
   
4. int stop_signal_called = false;
   
5. void sig_int_handle()
   
6. {
   
7. stop_signal_called = true;
   
8. }
   
9. int main()
   
10. {
    
11. std::string addr_args = " ";
    
12. uhd::usrp::multi_usrp::sptr usrp =uhd::usrp::multi_usrp::make(addr_args);
    
13. // set the clock source and clock rate
    
14. std::string ref = "internal";
    
15. usrp->set_clock_source(ref);
    
16. float clock_rate = 40e6;
    
17. usrp->set_master_clock_rate(clock_rate);
    
18. printf("set the clock rate %0.2f \n",usrp->get_master_clock_rate() );
    
19. // set the sample rate
    
20. float samp_rate = 20e6;
    
21. usrp->set_rx_rate(samp_rate);
    
22. printf("set the tx sample rate to %0.2f \n",usrp->get_rx_rate());
    
23. // set the center frequency
    
24. float center_freq = 2.412e9;
    
25. usrp->set_rx_freq(center_freq);
    
26. printf("set the tx center freq to %0.2f \n",usrp->get_rx_freq());
    
27. // set the rf gain
    
28. float rx_gain = 80;
    
29. usrp->set_rx_gain(rx_gain);
    
30. printf("set the tx gain to %0.2f \n",usrp->get_rx_gain());
    
31. std::string cpu_format = "fc32";
    
32. std::string wire_format = "sc16";
    
33. uhd::stream_args_t stream_args(cpu_format,wire_format);
    
34. uhd::rx_streamer::sptr rx_stream =usrp->get_rx_stream(stream_args);
    
35. uhd::rx_metadata_t md;
    
36. //uhd::stream_cmd_tstream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);
    
37. uhd::stream_cmd_tstream_cmd(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
    
38. stream_cmd.num_samps = SAMPLE_PER_BUFF;
    
39. stream_cmd.stream_now = true;
    
40. //stream_cmd.time_spec = uhd::time_spec_t();
    
41. stream_cmd.time_spec = usrp->get_time_now();
    
42. rx_stream->issue_stream_cmd(stream_cmd);
    
43. uint32_t buff[SAMPLE_PER_BUFF*2] = {0};
    
44. unsigned long long num_total_samps = 0;
    
45. while(!stop_signal_called)
    
46. {
    
47. //int num_rx_samps = rx_stream->recv(buff,SAMPLE_PER_BUFF, md);
    
48. memset(buff, 0, SAMPLE_PER_BUFF * sizeof(uint32_t));
    
49. int num_rx_samps = rx_stream->recv(buff,SAMPLE_PER_BUFF, md, 3.0, false);
    
50. if(md.error_code == uhd::rx_metadata_t::ERROR_CODE_TIMEOUT)
    
51. {
    
52. printf("Timeout while streaming......\n");
    
53. break;
    
54. }
    
55. if(md.error_code ==uhd::rx_metadata_t::ERROR_CODE_OVERFLOW)
    
56. {
    
57. printf("Overflowing while stream......\n");
    
58. continue;
    
59. }
    
60. if(md.error_code !=uhd::rx_metadata_t::ERROR_CODE_NONE)
    
61. {
    
62. //printf("Receive error: %s \n",md.strerror());
    
63. continue;
    
64. }
    
65. //rintf("num_rx_samps = %d\n",num_rx_samps);
    
66. num_total_samps += num_rx_samps;
    
67. }
    
68. printf("num_total_samps = %d \n",num_total_samps);
    
69. stream_cmd.stream_mode =uhd::stream_cmd_t::STREAM_MODE_STOP_CONTINUOUS;
    
70. rx_stream->issue_stream_cmd(stream_cmd);
    
71. return 0;
    
72. }

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编译

g++ 编译时需要链接uhd库，系统需提前安装UHD驱动。具体过程参见之前博客。Ubuntu14.04 源码安装 UHD3.8.0

1. g++ rx.cpp -o rx -luhd

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４. 结论

　　以上代码在Ubuntu上采用USRPB200测试通过。

　　掌握UHD库函数的使用、g++链接 UHD库等是基于USRP开发软件无线电项目的基础。之后，我们可以进一步设计发送程序和接收程序，用USRP搭建一套SDR 收发系统。