UHD C/C++ 程式設計例項 USRP傳送、接收資料
UHD C/C++ 程式設計例項 USRP傳送、接收資料
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1. UHD庫函式簡介
1.1 傳送函式
新建一個usrp裝置std::string args = " "; args指定USRP地址，配置USRP引數等uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(args);
設定時鐘源和時鐘頻率std::string ref = "internal"; // internal, external, MIMO.
usrp->set_clock_source(ref);double rate = 40e6;usrp->set_master_clock_rate(rate);
usrp->get_clock_source() //獲取當前的時鐘源usrp->get_clock_sources() //獲取所有可用的時鐘源usrp->get_master_clock_rate(); //獲取時鐘頻率
設定取樣率double samp_rate = 20e6;usrp->set_tx_rate(samp_rate);
usrp->get_tx_rate() //獲取當前的取樣率usrp->get_tx_rates() //獲取取樣率的取樣範圍
設定發射中心頻點double freq = 2.412e9;usrp->set_tx_freq(freq);
usrp->get_fe_tx_freq_range();usrp->get_tx_freq();usrp->get_tx__freq_range();
設定發射增益double tx_gain = 60;usrp->set_tx_gain(tx_gain);
設定發射天線
預設情況下無需設定發射天線，如需指定特定發射天線時設定。usrp->set_tx_antenna(0);usrp->get_tx_antenna();usrp->get_tx_antennas();
建立傳送流
新建傳送流引數std::string cpu_format = "fc32";
目前cpu_format支援的型別有：fc64 - complex fc32 - complex sc16 - complex sc8 - complexstd::string wire_format = "sc16";
目前wire_format支援的型別有：sc16 - Q16 I16 sc8 - Q8_1 I8_1 Q8_0 I8_0
uhd::stream_args_t stream_args(cpu_format, wire_format);uhd::tx_streamer::sptr tx_stream = usrp->get_tx_stream(stream_args);
中頻資料管理uhd::tx_metada_t md; //結構體描述接收到的中頻訊號md.start_of_burst = false; // 設定為真的時候傳送第一個資料包md.end_of_burst = false; // 設定為真的時候傳送最後一個數據包md.has_time_spec = false; // 設定為false時立即傳送，設定為真的時候在特定時間傳送
1.2 接收函式
建立一個usrpstd::string args = " ";uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(args);
設定時鐘源和時鐘頻率std::string ref = "internal"; //internal, external and MIMOusrp->set_clock_source(ref);
double clock_rate = 40e6;usrp->set_master_clock_rate(clock_rate);
設定取樣率double rate = 20e6;usrp->set_rx_rate(rate);
設定中心頻率double freq = 2.412e9;usrp->set_rx_freq(freq);
設定增益double rx_gain = 50;usrp->set_rx_gain(rx_gain);
建立接收流std::string cpu_format = "fc32";std::string wire_format = "sc16";uhd::stream_args_t stream_args(cpu_format, wire_format);uhd::rx_streamer::sptr rx_stream = usrp->get_rx_stream(stream_args);
設定接收模式uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
//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
stream_cmd.num_samps = 1000; // 接收取樣點數stream_cmd.stream_now = true; //現在開始接收rx_stream->issue_stream_cmd(stream_cmd); //配置rx_stream引數
2. USRP傳送資料
程式碼實現USRP傳送二進位制檔案802.11a_BUPT41.seg內的資料。裡面的資料為float complex型別，複數的實部和虛部交替儲存。即如下圖所示。使用者可以把要傳送的資料生成對應的二進位制檔案，也可以直接寫成陣列放在程式碼中。注意：float型別資料的單位1就是 “1”。
原始碼
#include <uhd/usrp/multi_usrp.hpp>
#include <signal.h>
#define SAMPLE_PER_BUFF 2000
int stop_signal_called = 0;
void sig_int_handle(int)
{
stop_signal_called = 1;
printf("stop tx.........\n");
exit(0);
}
int main()
{
std::string addr_args = " ";
uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(addr_args);
printf("Create a usrp......\n");
// set the ref and clock rate
std::string ref = "internal";
usrp->set_clock_source(ref);
float clock_rate = 40e6;
usrp->set_master_clock_rate(clock_rate);
printf("set the clock rate %0.2f \n", usrp->get_master_clock_rate() );
// set the sample rate
float samp_rate = 20e6;
usrp->set_tx_rate(samp_rate);
printf("set the tx sample rate to %0.2f \n", usrp->get_tx_rate());
// set the center frequency
float center_freq = 2.412e9;
usrp->set_tx_freq(center_freq);
printf("set the tx center freq to %0.2f \n", usrp->get_tx_freq());
// set the rf gain
float tx_gain = 90;
usrp->set_tx_gain(tx_gain);
printf("set the tx gain to %0.2f \n", usrp->get_tx_gain());
// create a tx stream
std::string cpu_format = "fc32";
std::string wire_format = "sc16";
uhd::stream_args_t stream_args(cpu_format, wire_format);
uhd::tx_streamer::sptr tx_stream = usrp->get_tx_stream(stream_args);
uhd::tx_metadata_t md;
// catch the INT signal
signal(SIGINT, sig_int_handle);
float read_buff[SAMPLE_PER_BUFF * 2] = {0};
while(!stop_signal_called)
{
FILE *fp = fopen("802.11a_BUPT41.seg", "rb");
md.start_of_burst = false;
md.end_of_burst = false;
while( (!md.end_of_burst) && (!stop_signal_called) )
{
int read_length = 0;
if( (read_length = fread(read_buff, sizeof(uint32_t), SAMPLE_PER_BUFF * 2, fp) ) == (SAMPLE_PER_BUFF * 2) )
{
//int index;
//for(index = 0; index < SAMPLE_PER_BUFF * 2; index++)
// printf("%0.2f ", read_buff[index]);
//puts("");
//md.start_of_burst = true;
tx_stream->send(read_buff, SAMPLE_PER_BUFF, md);
//md.start_of_burst = false;
//sleep(1);
}
else if(read_length >= 0)
{
md.end_of_burst = true;
}
}
fclose(fp);
}
return 0;
}
編譯
g++ 編譯時需要連結uhd庫，系統需提前安裝UHD驅動。具體過程參見之前部落格。Ubuntu14.04 原始碼安裝 UHD3.8.0g++ tx.cpp -o tx -luhd
3. USRP接收資料
啟動USRP，並使USRP一直接收資料。
原始碼
#include <uhd/usrp/multi_usrp.hpp>
#include <csignal>
#define SAMPLE_PER_BUFF 2000
int stop_signal_called = false;
void sig_int_handle()
{
stop_signal_called = true;
}
int main()
{
std::string addr_args = " ";
uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(addr_args);
// set the clock source and clock rate
std::string ref = "internal";
usrp->set_clock_source(ref);
float clock_rate = 40e6;
usrp->set_master_clock_rate(clock_rate);
printf("set the clock rate %0.2f \n", usrp->get_master_clock_rate() );
// set the sample rate
float samp_rate = 20e6;
usrp->set_rx_rate(samp_rate);
printf("set the tx sample rate to %0.2f \n", usrp->get_rx_rate());
// set the center frequency
float center_freq = 2.412e9;
usrp->set_rx_freq(center_freq);
printf("set the tx center freq to %0.2f \n", usrp->get_rx_freq());
// set the rf gain
float rx_gain = 80;
usrp->set_rx_gain(rx_gain);
printf("set the tx gain to %0.2f \n", usrp->get_rx_gain());
std::string cpu_format = "fc32";
std::string wire_format = "sc16";
uhd::stream_args_t stream_args(cpu_format, wire_format);
uhd::rx_streamer::sptr rx_stream = usrp->get_rx_stream(stream_args);
uhd::rx_metadata_t md;
//uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);
uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_START_CONTINUOUS);
stream_cmd.num_samps = SAMPLE_PER_BUFF;
stream_cmd.stream_now = true;
//stream_cmd.time_spec = uhd::time_spec_t();
stream_cmd.time_spec = usrp->get_time_now();
rx_stream->issue_stream_cmd(stream_cmd);
uint32_t buff[SAMPLE_PER_BUFF*2] = {0};
unsigned long long num_total_samps = 0;
while(!stop_signal_called)
{
//int num_rx_samps = rx_stream->recv(buff, SAMPLE_PER_BUFF, md);
memset(buff, 0, SAMPLE_PER_BUFF * sizeof(uint32_t));
int num_rx_samps = rx_stream->recv(buff, SAMPLE_PER_BUFF, md, 3.0, false);
if(md.error_code == uhd::rx_metadata_t::ERROR_CODE_TIMEOUT)
{
printf("Timeout while streaming......\n");
break;
}
if(md.error_code == uhd::rx_metadata_t::ERROR_CODE_OVERFLOW)
{
printf("Overflowing while stream......\n");
continue;
}
if(md.error_code != uhd::rx_metadata_t::ERROR_CODE_NONE)
{
//printf("Receive error: %s \n", md.strerror());
continue;
}
//printf("num_rx_samps = %d \n",num_rx_samps);
num_total_samps += num_rx_samps;
}
printf("num_total_samps = %d \n", num_total_samps);
stream_cmd.stream_mode = uhd::stream_cmd_t::STREAM_MODE_STOP_CONTINUOUS;
rx_stream->issue_stream_cmd(stream_cmd);
return 0;
}編譯
g++ 編譯時需要連結uhd庫，系統需提前安裝UHD驅動。具體過程參見之前部落格。Ubuntu14.04 原始碼安裝 UHD3.8.0g++ rx.cpp -o rx -luhd
４. 結論
以上程式碼在Ubuntu上採用USRP B200測試通過。
掌握UHD庫函式的使用、g++ 連結 UHD庫等是基於USRP開發軟體無線電專案的基礎。之後，我們可以進一步設計傳送程式和接收程式，用USRP搭建一套SDR 收發系統。