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//loop until the entire file has been read

    infile.read((char*)&buff.front(), buff.size()*sizeof(samp_type));
    size_t num_tx_samps = infile.gcount()/sizeof(samp_type);

    md.end_of_burst = infile.eof();

 //loop until the entire file has been read

     infile.read((char*)&buff.front(), buff.size()*sizeof(samp_type));
     size_t num_tx_samps = infile.gcount()/sizeof(samp_type);

     md.end_of_burst = infile.eof();

 //loop until the entire file has been read

     infile.read((char*)&buff.front(), buff.size()*sizeof(samp_type));
     size_t num_tx_samps = infile.gcount()/sizeof(samp_type);

     md.end_of_burst = infile.eof();

 //loop until the entire file has been read

     infile.read((char*)&buff.front(), buff.size()*sizeof(samp_type));
     size_t num_tx_samps = infile.gcount()/sizeof(samp_type);

     md.end_of_burst = infile.eof();

 Hi Rob,

 Yes, it includes "--ref external". Here's the complete line:
 tx_samples_from_file.exe --args addr=192.168.140.2 --file
 noise_10msps.bin --rate 10000000 --freq 1000000000 --gain 0 --ref
 external --repeat

 Here's the complete output of the execution. We really see that
 the external reference is used.

 Creating the usrp device with: addr=192.168.140.2...
 -- X300 initialization sequence...
 -- Determining maximum frame size... 8000 bytes.
 -- Setup basic communication...
 -- Loading values from EEPROM...
 -- Setup RF frontend clocking...
 -- Radio 1x clock:200
 -- Initialize Radio control...
 -- Creating WSA UDP transport for 192.168.140.2:49153
 <http://192.168.140.2:49153>
 -- Performing register loopback test... pass
 -- Creating WSA UDP transport for 192.168.140.2:49153
 <http://192.168.140.2:49153>
 -- Performing register loopback test... pass
 -- Initializing clock and time using internal sources... done
 Setting Clock Source to: external
 Setting Time Source to: external
 Using Device: Single USRP:
   Device: X-Series Device
   Mboard 0: X300
   RX Channel: 0
     RX DSP: 0
     RX Dboard: A
     RX Subdev: WBX-120 RX+GDB
   RX Channel: 1
     RX DSP: 1
     RX Dboard: B
     RX Subdev: WBX-120 RX+GDB
   TX Channel: 0
     TX DSP: 0
     TX Dboard: A
     TX Subdev: WBX-120 TX+GDB
   TX Channel: 1
     TX DSP: 1
     TX Dboard: B
     TX Subdev: WBX-120 TX+GDB

 Setting TX Rate: 10.000000 Msps...
 Actual TX Rate: 10.000000 Msps...

 Setting TX Freq: 1000.000000 MHz...
 -- Successfully tuned to 1000.000000 MHz
 --
 -- Successfully tuned to 1000.000000 MHz
 --
 Actual TX Freq: 1000.000000 MHz...

 Setting TX Gain: 0.000000 dB...
 Actual TX Gain: 0.000000 dB...

 Checking TX: LO: locked ...
 Checking TX: Ref: locked ...
 Press Ctrl + C to stop streaming...
 --> create a transmit streamer
 -- Creating WSA UDP transport for 192.168.140.2:49153
 <http://192.168.140.2:49153>
 -- Creating WSA UDP transport for 192.168.140.2:49153
 <http://192.168.140.2:49153>
 --     1) catch time transition at pps edge
 --     2) set times next pps (synchronously)
 --> loop until the entire file has been read

 2015-02-19 10:33 GMT-05:00 Robert Kossler
 <Robert.D.Kossler.3@nd.edu <mailto:Robert.D.Kossler.3@nd.edu>>:

     Hi Serge,
     What is your command line?  I assume it includes "--ref=external"?
     Rob

     On Wed, Feb 18, 2015 at 2:50 PM, Serge Malo via USRP-users
     <usrp-users@lists.ettus.com
     <mailto:usrp-users@lists.ettus.com>> wrote:

         Hi all,

         I'm developing an application where I need to transmit 2
         signals on the 2 channels of a x300.
         The beginning of the Tx streaming of the 2 signals need to
         be tightly synchronized (less than 5ns time offset between
         them).

         Now, I'm only trying to verify that the time offset
         between the 2 channels can be less than 5ns,  with a
         modified UHD example (tx_samples_from_file).
         I'm simply streaming the same file to both channels, and
         verifying the time offset between the 2 channels with an
         external instrument.
         So far, I'm not getting good results: 
         I'm getting time offsets in the order of 6000-22000 ns.
         The value is quite stable from one run to another (~50ns),
         but it varies by more than 1us when I change the central
         frequency.

         I attach my modified example source code.
         I'm using UHD 3.8.2, but I had the same results with UHD
         3.8.1.
         I'm running under Windows 7, but I also had the same
         results under Linux.
         My x300 has 2 WBX-120 D/B.
         Its using a 10MHz external Reference Clock (Wenzel) and an
         external PPS signal coming out of UBlox GPS receiver.

         Below, I show how I "prepare" the file streaming to
         synchronize the 2 channels.
         Please, let me know if you see something wrong in this
         sequence.

         Best Regards,
         Serge

         std::vector<const void *> buffs;
         buffs.push_back(&buff.front());
         buffs.push_back(&buff.front());

         uhd::tx_metadata_t md;
         md.start_of_burst = false;
         md.end_of_burst = false;
         md.has_time_spec = true;

         usrp->set_time_unknown_pps(uhd::time_spec_t(0.0));
         boost::this_thread::sleep(boost::posix_time::seconds(2));
         //allow for some setup time

         uhd::time_spec_t futureTime(2.0);
         futureTime += usrp->get_time_now();
         md.time_spec = futureTime;

             //loop until the entire file has been read
         std::cout << "--> loop until the entire file has been
         read" << std::endl;
             while(not md.end_of_burst and not stop_signal_called){

                 infile.read((char*)&buff.front(),
         buff.size()*sizeof(samp_type));
                 size_t num_tx_samps =
         infile.gcount()/sizeof(samp_type);

                 md.end_of_burst = infile.eof();
         md.has_time_spec = false;

         //tx_stream->send(&buff.front(), num_tx_samps, md);
         tx_stream->send(buffs, num_tx_samps, md);
         }

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 -- 
 *Serge Malo *
 CDO & Co-founder, Skydel Solutions
 Cell: 1-514-294-4017 <tel:1-514-294-4017>
 Skype: sergemalo2000
 Serge.Malo@SkydelSolutions.com <mailto:Serge.Malo@SkydelSolutions.com>

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  //loop until the entire file has been read

      infile.read((char*)&buff.front(),

      md.end_of_burst = infile.eof();

usrp-users@lists.ettus.com

x300: Unable to get Tight Syncrhonization between 2 Tx channels

Setting TX Freq: 1000.000000 MHz... -- Successfully tuned to 1000.000000 MHz

-- Successfully tuned to 1000.000000 MHz

Setting TX Freq: 1000.000000 MHz... -- Successfully tuned to 1000.000000 MHz

-- Successfully tuned to 1000.000000 MHz

Setting TX Freq: 1000.000000 MHz... -- Successfully tuned to 1000.000000 MHz

-- Successfully tuned to 1000.000000 MHz

Setting TX Freq: 1000.000000 MHz...
-- Successfully tuned to 1000.000000 MHz

Setting TX Freq: 1000.000000 MHz...
-- Successfully tuned to 1000.000000 MHz

Setting TX Freq: 1000.000000 MHz...
-- Successfully tuned to 1000.000000 MHz