//variables to be set by po
std::string args, sync, subdev, channel_list,file,file0,file1;
double seconds_in_future, freq;
size_t total_num_samps;
double rate,gain,tx_gain;
std::ofstream outfile,outfile2;

//setup the program options
po::options_description desc("Allowed options");
desc.add_options()
    ("help", "help message")
    ("args", po::value<std::string>(&args)->default_value(""), "single uhd device address args")
    ("file", po::value<std::string>(&file)->default_value("measure0-1"), "name of the file to write binary samples to")
    ("secs", po::value<double>(&seconds_in_future)->default_value(1.0), "number of seconds in the future to receive")
    ("nsamps", po::value<size_t>(&total_num_samps)->default_value(10000), "total number of samples to receive")
    ("rate", po::value<double>(&rate)->default_value(8e6), "rate of incoming samples")
    ("sync", po::value<std::string>(&sync)->default_value("b210"), "synchronization method: now, pps, mimo")
    ("freq", po::value<double>(&freq)->default_value(800e6), "RF center frequency in Hz")
    ("gain", po::value<double>(&gain), "gain for the RF chain")
    ("tx-gain", po::value<double>(&tx_gain), "gain for the TX in calibration Mode")
    ("subdev", po::value<std::string>(&subdev), "subdev spec (homogeneous across motherboards)")
    ("v", "specify to enable inner-loop verbose")
    ("calc","specify to enable transmitting and recording of calibration data")
    ("channels", po::value<std::string>(&channel_list)->default_value("0"), "which channel(s) to use (specify \"0\", \"1\", \"0,1\", etc)")
;
po::variables_map vm;
po::store(po::parse_command_line(argc, argv, desc), vm);
po::notify(vm);

//print the help message
if (vm.count("help")){
    std::cout << boost::format("UHD RX Multi Samples %s") % desc << std::endl;
    std::cout <<
    "    This is a demonstration of how to receive aligned data from multiple channels.\n"
    "    This example can receive from multiple DSPs, multiple motherboards, or both.\n"
    "    The MIMO cable or PPS can be used to synchronize the configuration. See --sync\n"
    "\n"
    "    Specify --subdev to select multiple channels per motherboard.\n"
    "      Ex: --subdev=\"0:A 0:B\" to get 2 channels on a Basic RX.\n"
    "\n"
    "    Specify --args to select multiple motherboards in a configuration.\n"
    "      Ex: --args=\"addr0=192.168.10.2, addr1=192.168.10.3\"\n"
    << std::endl;
    return ~0;
}

bool verbose = vm.count("v") == 1;
bool calibration = vm.count("calc") == 1;



/**************** RX Init *************************************************/
//create a usrp device
std::cout << std::endl;
std::cout << boost::format("Creating the usrp device with: %s...") % args << std::endl;
uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(args);

usrp->set_master_clock_rate(30e6); //less then 30.72e6 //Möglichkeit 1: Variable Clock-Rate
//always select the subdevice first, the channel mapping affects the other settings
if (vm.count("subdev")){
    uhd::usrp::subdev_spec_t subdevClass = subdev;
    std::cout << subdevClass.to_pp_string() << std::endl;
    usrp->set_rx_subdev_spec(subdevClass); //sets across all mboards
}

std::cout << boost::format("Using Device: %s") % usrp->get_pp_string() << std::endl;

//set the rx sample rate (sets across all channels)
std::cout << boost::format("Setting RX Rate: %f Msps... ") % (rate/1e6) << std::endl;
usrp->set_rx_rate(rate);
std::cout << boost::format("Actual RX Rate: %f Msps...") % (usrp->get_rx_rate()/1e6) << std::endl << std::endl;

//set center Frequency
std::cout << boost::format("Setting RX Freq: %f MHz...") % (freq/1e6) << std::endl;
uhd::tune_request_t tune_request(freq);
for(size_t i=0;i<usrp->get_rx_num_channels();i++)
    usrp->set_rx_freq(tune_request,i);
std::cout << boost::format("Actual RX Freq: %f MHz...") % (usrp->get_rx_freq(1)/1e6) << std::endl << std::endl;

//set the rf gain
if (vm.count("gain")){
    for(size_t i=0;i<usrp->get_rx_num_channels();i++){
        std::cout << boost::format("Setting RX Gain for Channel %d: %f dB...") % i % gain << std::endl;
        usrp->set_rx_gain(gain,i);
        std::cout << boost::format("Actual RX Gain: %f dB...") % usrp->get_rx_gain() << std::endl << std::endl;
    }
}

//open files to write
if(calibration) file+=".calc"; //Kalibrierdaten mit Endung .calc
else    file+=".dat";   //Messdaten mit Endung.dat
file0 = file;
file1 = file;
file0 += "0";
file1 += "1";

outfile.open(file0.c_str(), std::ofstream::binary);
if(usrp->get_rx_num_channels()>1){
    outfile2.open(file1.c_str(),std::ofstream::binary);
}



/**************** Recieve Start ******************************************/
//create a receive streamer
//linearly map channels (index0 = channel0, index1 = channel1, ...)
uhd::stream_args_t stream_args("sc16"); //complex short

//stream_args.channels = channel_nums;
for (size_t i = 0; i < usrp->get_rx_num_channels(); i++)
    stream_args.channels.push_back(i);
uhd::rx_streamer::sptr rx_stream = usrp->get_rx_stream(stream_args);

//setup streaming
std::cout << std::endl;
std::cout << boost::format(
    "Begin receiving of %u samples. Start in %f seconds in the future..."
) % total_num_samps % seconds_in_future << std::endl;
uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE);
stream_cmd.num_samps = total_num_samps;
stream_cmd.stream_now = false;
stream_cmd.time_spec = uhd::time_spec_t(seconds_in_future) + usrp->get_time_now();
rx_stream->issue_stream_cmd(stream_cmd); //tells all channels to stream

//meta-data will be filled in by recv()
uhd::rx_metadata_t md;

//allocate buffers to receive with samples (one buffer per channel)
const size_t samps_per_buff = rx_stream->get_max_num_samps();
std::vector<std::vector<std::complex<short> > > buffs(
    usrp->get_rx_num_channels(), std::vector<std::complex<short> >(samps_per_buff)
);

//create a vector of pointers to point to each of the channel buffers
std::vector<std::complex<short> *> buff_ptrs;
for (size_t i = 0; i < buffs.size(); i++) buff_ptrs.push_back(&buffs[i].front());

//the first call to recv() will block this many seconds before receiving
double timeout = seconds_in_future + 1; //timeout (delay before receive + padding)

size_t num_acc_samps = 0; //number of accumulated samples
while(num_acc_samps < total_num_samps){
    //receive a single packet
    size_t num_rx_samps = rx_stream->recv(
        buff_ptrs, samps_per_buff, md, timeout
    );

    //use a small timeout for subsequent packets
    timeout = 0.1;

    //handle the error code
    if (md.error_code == uhd::rx_metadata_t::ERROR_CODE_TIMEOUT) break;
    if (md.error_code != uhd::rx_metadata_t::ERROR_CODE_NONE){
        throw std::runtime_error(str(boost::format(
            "Receiver error %s"
        ) % md.strerror()));
    }

    if(verbose) std::cout << boost::format(
        "Received packet: %u samples, %u full secs, %f frac secs"
    ) % num_rx_samps % md.time_spec.get_full_secs() % md.time_spec.get_frac_secs() << std::endl;

    //Schreiben der gelesenen Werte in die Dateien
    if(outfile.is_open())
        outfile.write((const char *)&buffs[0].front(),num_rx_samps*sizeof(buffs[0].front()));
    if(outfile2.is_open())
        outfile2.write((const char *)&buffs[1].front(),num_rx_samps*sizeof(buffs[1][0]));

    num_acc_samps += num_rx_samps;
}

if (num_acc_samps < total_num_samps) std::cerr << "Receive timeout before all samples received..." << std::endl;
/**************************** Recieve End *******************************************************/
if(outfile.is_open())
    outfile.close();
if(outfile2.is_open())
    outfile2.close();

//finished
std::cout << std::endl << "Done! Mine" << std::endl << std::endl;

return EXIT_SUCCESS;

Hi, thank you for your notes. Today I had the chance to test them. Marcus Leech: > What are you passing in for the subdev argument? I pass "A:A A:B" > What does usrp->get_rx_num_channels() Return in this example? it returns "2" > Have you confirmed that your splitter is 0deg across all the frequencies you care about? I confirmed my Test Setup with an oscilloscope. The phase shift after splitter and cabel is only a few degrees and not more than 180 degrees. Sivan: > make calibration procedure on the USRP I'm not sure which calibration you mean. The function "uhd_cal_rx_iq_balance" returns Error: This board does not have the CAL antenna option, cannot self-calibrate. Rob Kossler: >check for LO locked: I've implemented your sensor test function. The b210-board has only one sensor. It's for the external refrence clock. I apply an externel 10 MHz Source and get a refrence Lock out of the PLL, but with out any improvment. >Regarding the phase offset, is it just a calibration issue? If you measure a phase offset with a ref signal and then later measure a real signal and apply the cal offset, does that fix your issue? I thought about this solution too. But the problem is, the phase offset differs after retuning. So I need to calibrate after each retune. Do you have any futher ideas. Regards, Stefan Ereth ----- Ursprüngliche Mail ----- Von: "Robert Kossler" <Robert.D.Kossler.3@nd.edu> An: "Stefan Ereth" <ErethSt42913@th-nuernberg.de> CC: "usrp-users@lists.ettus.com" <usrp-users@lists.ettus.com> Gesendet: Freitag, 2. Mai 2014 18:01:31 GMT +01:00 Amsterdam/Berlin/Bern/Rom/Stockholm/Wien Betreff: RE: [USRP-users] Phase Offset between USRP-B210 Channels Hi Stefan, Regarding your code, I noticed that it is streaming the 2 RX channels to file. I have also modified some Ettus examples to do this same task (see attached). It is based on rx_samples_to_file and benchmark_rate rather than rx_multi_samples. One reason I chose to modify the rx_samples_to_file example was that it included an LO Locked verification. Not sure if that could affect your results by not doing this check... Regarding the phase offset, is it just a calibration issue? If you measure a phase offset with a ref signal and then later measure a real signal and apply the cal offset, does that fix your issue? Rob Kossler -----Original Message----- From: USRP-users [mailto:usrp-users-bounces@lists.ettus.com] On Behalf Of Stefan Ereth via USRP-users Sent: Friday, May 02, 2014 2:30 AM To: usrp-users@lists.ettus.com Subject: [USRP-users] Phase Offset between USRP-B210 Channels Hi all, I'm saving IQ-Samples from both Channels of an USRP B210 for Direction of Arrival Estimation with Music. My source Code is based on the rx_multi_samples.cpp example. For tests I connected a sine-generator with a splitter to both channels. With a pulse sine a verified that the measured data is time aligned. (picture abs_pulse_sine in appendix) But the problem is, that there is a phase offset between the two channels of more than 180 degree. (picture real_sine and phase_diff) This offset varies by retuning. I don't understand where this phase offset come from, because the LO of both channels is in the same Chip and should be phase aligned. Is this a known problem of the B210? Or is there an error in my source code? Regards, Stefan Ereth // // Copyright 2011 Ettus Research LLC // // This program is free software: you can redistribute it and/or modify // it under the terms of the GNU General Public License as published by // the Free Software Foundation, either version 3 of the License, or // (at your option) any later version. // // This program is distributed in the hope that it will be useful, // but WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the // GNU General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program. If not, see <http://www.gnu.org/licenses/>. // #define use_short #include <uhd/utils/thread_priority.hpp> #include <uhd/utils/safe_main.hpp> #include <uhd/usrp/multi_usrp.hpp> #include <boost/program_options.hpp> #include <boost/format.hpp> #include <boost/thread.hpp> #include <boost/lexical_cast.hpp> #include <boost/algorithm/string.hpp> #include <iostream> #include <fstream> #include <complex> namespace po = boost::program_options; int UHD_SAFE_MAIN(int argc, char *argv[]){ uhd::set_thread_priority_safe(); //variables to be set by po std::string args, sync, subdev, channel_list,file,file0,file1; double seconds_in_future, freq; size_t total_num_samps; double rate,gain,tx_gain; std::ofstream outfile,outfile2; //setup the program options po::options_description desc("Allowed options"); desc.add_options() ("help", "help message") ("args", po::value<std::string>(&args)->default_value(""), "single uhd device address args") ("file", po::value<std::string>(&file)->default_value("measure0-1"), "name of the file to write binary samples to") ("secs", po::value<double>(&seconds_in_future)->default_value(1.0), "number of seconds in the future to receive") ("nsamps", po::value<size_t>(&total_num_samps)->default_value(10000), "total number of samples to receive") ("rate", po::value<double>(&rate)->default_value(8e6), "rate of incoming samples") ("sync", po::value<std::string>(&sync)->default_value("b210"), "synchronization method: now, pps, mimo") ("freq", po::value<double>(&freq)->default_value(800e6), "RF center frequency in Hz") ("gain", po::value<double>(&gain), "gain for the RF chain") ("tx-gain", po::value<double>(&tx_gain), "gain for the TX in calibration Mode") ("subdev", po::value<std::string>(&subdev), "subdev spec (homogeneous across motherboards)") ("v", "specify to enable inner-loop verbose") ("calc","specify to enable transmitting and recording of calibration data") ("channels", po::value<std::string>(&channel_list)->default_value("0"), "which channel(s) to use (specify \"0\", \"1\", \"0,1\", etc)") ; po::variables_map vm; po::store(po::parse_command_line(argc, argv, desc), vm); po::notify(vm); //print the help message if (vm.count("help")){ std::cout << boost::format("UHD RX Multi Samples %s") % desc << std::endl; std::cout << " This is a demonstration of how to receive aligned data from multiple channels.\n" " This example can receive from multiple DSPs, multiple motherboards, or both.\n" " The MIMO cable or PPS can be used to synchronize the configuration. See --sync\n" "\n" " Specify --subdev to select multiple channels per motherboard.\n" " Ex: --subdev=\"0:A 0:B\" to get 2 channels on a Basic RX.\n" "\n" " Specify --args to select multiple motherboards in a configuration.\n" " Ex: --args=\"addr0=192.168.10.2, addr1=192.168.10.3\"\n" << std::endl; return ~0; } bool verbose = vm.count("v") == 1; bool calibration = vm.count("calc") == 1; /**************** RX Init *************************************************/ //create a usrp device std::cout << std::endl; std::cout << boost::format("Creating the usrp device with: %s...") % args << std::endl; uhd::usrp::multi_usrp::sptr usrp = uhd::usrp::multi_usrp::make(args); usrp->set_master_clock_rate(30e6); //less then 30.72e6 //Möglichkeit 1: Variable Clock-Rate //always select the subdevice first, the channel mapping affects the other settings if (vm.count("subdev")){ uhd::usrp::subdev_spec_t subdevClass = subdev; std::cout << subdevClass.to_pp_string() << std::endl; usrp->set_rx_subdev_spec(subdevClass); //sets across all mboards } std::cout << boost::format("Using Device: %s") % usrp->get_pp_string() << std::endl; //set the rx sample rate (sets across all channels) std::cout << boost::format("Setting RX Rate: %f Msps... ") % (rate/1e6) << std::endl; usrp->set_rx_rate(rate); std::cout << boost::format("Actual RX Rate: %f Msps...") % (usrp->get_rx_rate()/1e6) << std::endl << std::endl; //set center Frequency std::cout << boost::format("Setting RX Freq: %f MHz...") % (freq/1e6) << std::endl; uhd::tune_request_t tune_request(freq); for(size_t i=0;i<usrp->get_rx_num_channels();i++) usrp->set_rx_freq(tune_request,i); std::cout << boost::format("Actual RX Freq: %f MHz...") % (usrp->get_rx_freq(1)/1e6) << std::endl << std::endl; //set the rf gain if (vm.count("gain")){ for(size_t i=0;i<usrp->get_rx_num_channels();i++){ std::cout << boost::format("Setting RX Gain for Channel %d: %f dB...") % i % gain << std::endl; usrp->set_rx_gain(gain,i); std::cout << boost::format("Actual RX Gain: %f dB...") % usrp->get_rx_gain() << std::endl << std::endl; } } //open files to write if(calibration) file+=".calc"; //Kalibrierdaten mit Endung .calc else file+=".dat"; //Messdaten mit Endung.dat file0 = file; file1 = file; file0 += "0"; file1 += "1"; outfile.open(file0.c_str(), std::ofstream::binary); if(usrp->get_rx_num_channels()>1){ outfile2.open(file1.c_str(),std::ofstream::binary); } /**************** Recieve Start ******************************************/ //create a receive streamer //linearly map channels (index0 = channel0, index1 = channel1, ...) uhd::stream_args_t stream_args("sc16"); //complex short //stream_args.channels = channel_nums; for (size_t i = 0; i < usrp->get_rx_num_channels(); i++) stream_args.channels.push_back(i); uhd::rx_streamer::sptr rx_stream = usrp->get_rx_stream(stream_args); //setup streaming std::cout << std::endl; std::cout << boost::format( "Begin receiving of %u samples. Start in %f seconds in the future..." ) % total_num_samps % seconds_in_future << std::endl; uhd::stream_cmd_t stream_cmd(uhd::stream_cmd_t::STREAM_MODE_NUM_SAMPS_AND_DONE); stream_cmd.num_samps = total_num_samps; stream_cmd.stream_now = false; stream_cmd.time_spec = uhd::time_spec_t(seconds_in_future) + usrp->get_time_now(); rx_stream->issue_stream_cmd(stream_cmd); //tells all channels to stream //meta-data will be filled in by recv() uhd::rx_metadata_t md; //allocate buffers to receive with samples (one buffer per channel) const size_t samps_per_buff = rx_stream->get_max_num_samps(); std::vector<std::vector<std::complex<short> > > buffs( usrp->get_rx_num_channels(), std::vector<std::complex<short> >(samps_per_buff) ); //create a vector of pointers to point to each of the channel buffers std::vector<std::complex<short> *> buff_ptrs; for (size_t i = 0; i < buffs.size(); i++) buff_ptrs.push_back(&buffs[i].front()); //the first call to recv() will block this many seconds before receiving double timeout = seconds_in_future + 1; //timeout (delay before receive + padding) size_t num_acc_samps = 0; //number of accumulated samples while(num_acc_samps < total_num_samps){ //receive a single packet size_t num_rx_samps = rx_stream->recv( buff_ptrs, samps_per_buff, md, timeout ); //use a small timeout for subsequent packets timeout = 0.1; //handle the error code if (md.error_code == uhd::rx_metadata_t::ERROR_CODE_TIMEOUT) break; if (md.error_code != uhd::rx_metadata_t::ERROR_CODE_NONE){ throw std::runtime_error(str(boost::format( "Receiver error %s" ) % md.strerror())); } if(verbose) std::cout << boost::format( "Received packet: %u samples, %u full secs, %f frac secs" ) % num_rx_samps % md.time_spec.get_full_secs() % md.time_spec.get_frac_secs() << std::endl; //Schreiben der gelesenen Werte in die Dateien if(outfile.is_open()) outfile.write((const char *)&buffs[0].front(),num_rx_samps*sizeof(buffs[0].front())); if(outfile2.is_open()) outfile2.write((const char *)&buffs[1].front(),num_rx_samps*sizeof(buffs[1][0])); num_acc_samps += num_rx_samps; } if (num_acc_samps < total_num_samps) std::cerr << "Receive timeout before all samples received..." << std::endl; /**************************** Recieve End *******************************************************/ if(outfile.is_open()) outfile.close(); if(outfile2.is_open()) outfile2.close(); //finished std::cout << std::endl << "Done! Mine" << std::endl << std::endl; return EXIT_SUCCESS; }