Problem with send() function making OOT

Hi all,

I am trying to make 2 TX 1Rx tagged stream block(OOT). For 1Tx 1Rx, it
was
working fine. I am trying to extend it. Now the problem is, I am not
being
able to configure the send() function.

If I try make test, it does not show any problem. However, when I check
after reception I find that 1 transmitter is transmitting, and another
is
not. I checked the every port of my USRP X310, it is working fine.

Here’s the code. I putting a short part where I have problem. Please
let
me if you need the header and grc file as well, to correct the code.


void

usrp_echotimer_cc_impl::send()

{

// Data to USRP

num_tx_samps = d_tx_stream->send(d_in_send1, total_num_samps,
d_metadata_tx, total_num_samps/(float)d_samp_rate+d_timeout_tx);

num_tx_samps = d_tx_stream->send(d_in_send0, total_num_samps,
d_metadata_tx, total_num_samps/(float)d_samp_rate+d_timeout_tx);

}

int

usrp_echotimer_cc_impl::work (int noutput_items,

gr_vector_int &ninput_items,

gr_vector_const_void_star &input_items,

gr_vector_void_star &output_items)

{

gr_complex *in0 = (gr_complex *) input_items[0];

gr_complex *in1 = (gr_complex *) input_items[1];

gr_complex *out = (gr_complex *) output_items[0];

// Set output items on packet length

noutput_items = ninput_items[0]=ninput_items[1];

// Resize output buffer

if(d_out_buffer.size()!=noutput_items)
d_out_buffer.resize(noutput_items);

// Send thread

d_in_send0 = in0;

d_in_send1 = in1;

d_noutput_items_send = noutput_items;

d_thread_send =
gr::thread::thread(boost::bind(&usrp_echotimer_cc_impl::send, this));

// Receive thread

d_out_recv = &d_out_buffer[0];

d_noutput_items_recv = noutput_items;

d_thread_recv =
gr::thread::thread(boost::bind(&usrp_echotimer_cc_impl::receive, this));


My system config is X310, daughterboard SBX-120 and I am using UHD-3.9

I checked the subdev specification, gain and frequency assignment. Those
are fine.

Please let me know how to correct and thanks in advance.

best regards

Sanjoy

Hi Sanjoy,

I am trying to make 2 TX 1Rx tagged stream block(OOT). For 1Tx 1Rx, it
was working fine. I am trying to extend it. Now the problem is, I am
not being able to configure the send() function.
Is there a particular reason you’re creating your own block? Is there a
feature missing on the USRP sink and source that come with gr-uhd?
If I try make test, it does not show any problem.
Since you wrote those tests: what are they covering?

your send() function looks a bit strange; what you’re doing is
transmitting two things on a single channel after each other. Also, what
you should be doing (from a programming style point of view) is pass the
buffers you want to send as references or something, but not save them
to class properties and then call send().
To send two buffers to two different channels, you will need to use a
vector containing the two buffers – have a look at rx_multi_samples;
that of course recv()s rather than sends(), but the semantics are the
same.

noutput_items = ninput_items[0]=ninput_items[1];
That’s wrong.
noutput_items is/given to you/ to let your work now how much it may
produce, that’s why it’s a parameter. overwriting that with the number
of input items in the 1st input stream doesn’t make much sense, and
setting ninput_items[0]=ninput_items[1] makes even less!
d_thread_send =
gr::thread::thread(boost::bind(&usrp_echotimer_cc_impl::send, this));
Uh-oh. This is where things will definitely go wrong. You break every
multithreading rule there is, by not restricting access to your internal
state, especially d_send_*! There’s no reason GNU Radio couldn’t already
call your work function again while usrp_echotimer_cc_impl::send()
hasn’t even started to transmit samples. Then, your d_send variables
will be overwritten. I really doubt this will work reliably, even in a
1TX 1RX configuration, but multithreading makes it really hard to notice
such mistakes.

I think what you’re trying to do is most probably already implemented in
the USRP sink and source blocks:

Since a single X310 is inherently coherent and has the same time, you
can simply use a USRP sink and a source, use set_start_time(…) on both
with the same time spec, and have your flow graph consume and produce
samples in different threads, coherently.

Best regards,
Marcus

Sorry, Sanjoy,

we’ll need some more information before we can give you better feedback.
It’s not clear exactly what you’re trying to achieve, and what exactly
is failing.

Perhaps this helps getting started:
http://gnuradio.org/redmine/projects/gnuradio/wiki/ReportingErrors

Cheers,
Martin

Hi Sanjoy,
Nice project!

With this, I am actually trying to achieve time sync for X310. With
separate UHD source and sink–I could not achieve time sync with
different ports.
That’s absolutely possible! Two channels in the same X310 have the same
clock and time source.

For example, generate a Flow graph with GRC with a USRP Source,
configure it to have 2 channels. This will automatically make sure that
these two channels are time-aligned.
If you have a sink in your flow graph, you can do exactly the same:
do the followin in your python file, just before tb.start() gets called:

now = usrp_source0.get_time_now() #or however your source is called
starttime = now + uhd.time_spec(1.5) #1.5 seconds in the future
usrp_source0.set_start_time(starttime)
usrp_sink0.set_start_time(starttime).

The multiple sample streams that now come out of the USRP source and go
into the USRP sink will now start exactly at the same time; that means,
there is (for a single sampling rate/master clock rate/frequency
combination) a static offset between RX and TX, due to the fact that the
TX timestamp applies to the point in time where a sample enters the DSP
chain on the X310, and the RX timestamp to the time it exits the DSP
chain.

If you have more than one X310, you will need to synchronize these by
means of hardware (e.g. external PPS) and use multiple addresses as the
USRP block’s address.

The code is from CEL,KIT --Echotimer. I tried it over X310, after using
the subdev_spec, it worked nicely for SISO. I am trying to use it for
MIMO. I am not really much good at this coding. I just started learning
it this month.
Echotimer was originally a tool used to calibrate out the static RX/TX
delay you get for the direct path between the radar TX antenna and RX
antenna. That offset was typically empirically observed and then used as
a parameter.
Now, for MIMO, the situation would be much more complex, because you
wouldn’t only have an offset between TX and RX, but also between
different TXes and RXes, if not the USRPs had the ability to be
coherent, based on timed commands (which you use by setting the start
time).
You can get the same behaviour for your MIMO case (that is, delay one
stream by a N samples) by just starting the USRP sink N/f_sample later,
using the set_start_time method.

Stefan’s Wunsch’s adaptation of echotimer in gr-radar has the advantage
that it is a tagged stream block, which is really handy for “bursty”
applications like radar. I don’t know if only getting bursts of data is
what you want, or if you’d prefer continuous sample streams like the UHD
sink and source give you.

There’s one thing that could use improvement in the echotimer code: If
the set_?x_freq() were done after the time and clock sources had been
set as a timed command (i.e. after calling set_command_time()), then the
SBX daughterboards would always have the same phase relationship after
tuning to the same frequency, which might be really handy in MIMO.

In its wholeness, your block looks a lot better! I’m especially relieved
by seeing the thread.join() methods being used to ensure that the block
waits long enough until samples have been sent and received.

Overall, I think you might want to try using the normal USRP sink and
USRP source, synchronizing them via timed commands (set_start_time) :slight_smile:
If they give you what you want, then you’re better off without
echotimer. If you really want to integrate echotimer into your own OOT
(instead of just relying on installing gr-radar, which would probably be
totally OK), you should make the “namespace … {” directive match your
OOT’s other blocks.

Best regards,
Marcus

Hi Marcus,
Thanks for the response. I did not get any notification in my inbox. So
I put it there.

I am trying to implement MIMO OFDM radar with X310.
With this, I am actually trying to achieve time sync for X310. With
separate UHD source and sink–I could not achieve time sync with
different ports.

The code is from CEL,KIT --Echotimer. I tried it over X310, after using
the subdev_spec, it worked nicely for SISO. I am trying to use it for
MIMO. I am not really much good at this coding. I just started learning
it this month.

I will try to correct the code with the points you mentioned.
I am putting the the impl.cc code, which is a bit large. But it would be
really kind if you can go through and find any further problem to
correct.

best regards
Sanjoy Basak
thesis student, IHE, KIT

The subdev spec and others I hardcoded those to check whether works or
not.

/* -- c++ -- /
/

  • Copyright 2014 Communications Engineering Lab, KIT.
  • This 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, or (at your option)
  • any later version.
  • This software 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 software; see the file COPYING. If not, write to
  • the Free Software Foundation, Inc., 51 Franklin Street,
  • Boston, MA 02110-1301, USA.
    */

#ifdef HAVE_CONFIG_H
#include “config.h”
#endif

#include <gnuradio/io_signature.h>
#include “usrp_echotimer_cc_impl.h”
#include

namespace gr {
namespace radar {

usrp_echotimer_cc::sptr
usrp_echotimer_cc::make(int samp_rate, float center_freq, int

num_delay_samps, std::string args_tx, std::string wire_tx, std::string
clock_source_tx, std::string time_source_tx, std::string antenna_tx1,
std::string antenna_tx2, float gain_tx, float timeout_tx, float wait_tx,
float lo_offset_tx, std::string wire_rx, std::string antenna_rx, float
gain_rx, float timeout_rx, float wait_rx, float lo_offset_rx,
std::string spec_tx, std::string spec_tx2, std::string spec_rx, const
std::string& len_key)
{
return gnuradio::get_initial_sptr
(new usrp_echotimer_cc_impl(samp_rate, center_freq,
num_delay_samps, args_tx, wire_tx, clock_source_tx, time_source_tx,
antenna_tx1, antenna_tx2, gain_tx, timeout_tx, wait_tx, lo_offset_tx,
wire_rx, antenna_rx, gain_rx, timeout_rx, wait_rx, lo_offset_rx,
spec_tx, spec_tx2, spec_rx, len_key));
}

/*
 * The private constructor
 */
usrp_echotimer_cc_impl::usrp_echotimer_cc_impl(int samp_rate, float

center_freq, int num_delay_samps, std::string args_tx, std::string
wire_tx, std::string clock_source_tx, std::string time_source_tx,
std::string antenna_tx1, std::string antenna_tx2, float gain_tx, float
timeout_tx, float wait_tx, float lo_offset_tx, std::string wire_rx,
std::string antenna_rx, float gain_rx, float timeout_rx, float wait_rx,
float lo_offset_rx, std::string spec_tx, std::string spec_tx2,
std::string spec_rx, const std::string& len_key)
: gr::tagged_stream_block(“usrp_echotimer_cc”,
gr::io_signature::make(2, 2, sizeof(gr_complex)),
gr::io_signature::make(1, 1, sizeof(gr_complex)), len_key)
{
d_samp_rate = samp_rate;
d_center_freq = center_freq;
d_num_delay_samps = num_delay_samps;
d_out_buffer.resize(0);

//***** Setup USRP TX *****//

d_spec_tx=spec_tx;
d_spec_tx2=spec_tx2;
d_args_tx = args_tx;
d_wire_tx = wire_tx;
d_clock_source_tx = clock_source_tx;
d_time_source_tx = time_source_tx;
d_antenna_tx1 = antenna_tx1;
d_antenna_tx2 = antenna_tx2;
d_lo_offset_tx = lo_offset_tx;
d_gain_tx = gain_tx;
d_timeout_tx = timeout_tx; // timeout for sending
d_wait_tx = wait_tx; // secs to wait befor sending

// Setup USRP TX: args (addr,...)
d_usrp_tx = uhd::usrp::multi_usrp::make(d_args_tx);
std::cout << "Using USRP Device (TX): " << std::endl <<

d_usrp_tx->get_pp_string() << std::endl;

//setup subdev spec
d_usrp_tx -> set_tx_subdev_spec ( uhd::usrp::subdev_spec_t ("B:0

A:0"));
//set_subdev_spec(const std::string &spec_tx, size_t mboard);

//setup subdev spec for tx2--same usrp
//d_usrp_tx -> set_tx_subdev_spec ( uhd::usrp::subdev_spec_t

(d_spec_tx2),0);

// Setup USRP TX: sample rate
std::cout << "Setting TX Rate: " << d_samp_rate << std::endl;
d_usrp_tx->set_tx_rate(d_samp_rate);
std::cout << "Actual TX Rate: " << d_usrp_tx->get_tx_rate() <<

std::endl;

// Setup USRP TX: gain
set_tx_gain(d_gain_tx);

// Setup USRP TX: tune request
d_tune_request_tx = uhd::tune_request_t(d_center_freq); // FIXME:

add alternative tune requests
d_usrp_tx->set_tx_freq(d_tune_request_tx);
//d_usrp_tx->set_tx_freq(d_tune_request_tx,1);

// Setup USRP TX: antenna
d_usrp_tx->set_tx_antenna(d_antenna_tx1,0);
d_usrp_tx->set_tx_antenna(d_antenna_tx2,1);

// Setup USRP TX: clock source
d_usrp_tx->set_clock_source(d_clock_source_tx); // Set TX clock, TX

is master

// Setup USRP TX: time source
d_usrp_tx->set_time_source(d_time_source_tx); // Set TX time, TX is

master
//d_usrp_tx->set_time_source(d_time_source_tx,1); // Set
TX time, TX is mast
// Setup USRP TX: timestamp
if(d_time_source_tx!=“gpsdo”){
d_usrp_tx->set_time_now(uhd::time_spec_t(0.0)); // Do set time on
startup if not gpsdo is activated.
}

// Setup transmit streamer
uhd::stream_args_t stream_args_tx("fc32", d_wire_tx); // complex

floats
d_tx_stream = d_usrp_tx->get_tx_stream(stream_args_tx);

//***** Setup USRP RX *****//

d_spec_rx=spec_rx;

d_args_rx = args_tx;
d_wire_rx = wire_rx;
d_clock_source_rx = clock_source_tx;
d_time_source_rx = time_source_tx;
d_antenna_rx = antenna_rx;
d_lo_offset_rx = lo_offset_rx;
d_gain_rx = gain_rx;
d_timeout_rx = timeout_rx; // timeout for receiving
d_wait_rx = wait_rx; // secs to wait befor receiving

// Setup USRP RX: args (addr,...)
d_usrp_rx = uhd::usrp::multi_usrp::make(d_args_rx);
std::cout << "Using USRP Device (RX): " << std::endl <<

d_usrp_rx->get_pp_string() << std::endl;

//setup subdev spec
d_usrp_rx -> set_rx_subdev_spec ( uhd::usrp::subdev_spec_t

(d_spec_rx));

// Setup USRP RX: sample rate
std::cout << "Setting RX Rate: " << d_samp_rate << std::endl;
d_usrp_rx->set_rx_rate(d_samp_rate);
std::cout << "Actual RX Rate: " << d_usrp_rx->get_rx_rate() <<

std::endl;

// Setup USRP RX: gain
set_rx_gain(d_gain_rx);

// Setup USRP RX: tune request
d_tune_request_rx = uhd::tune_request_t(d_center_freq,

d_lo_offset_rx); // FIXME: add alternative tune requests
d_usrp_rx->set_rx_freq(d_tune_request_rx);

// Setup USRP RX: antenna
d_usrp_rx->set_rx_antenna(d_antenna_rx);

// Setup USRP RX: clock source
d_usrp_rx->set_clock_source(d_clock_source_rx); // RX is slave,

clock is set on TX

// Setup USRP RX: time source
d_usrp_rx->set_time_source(d_time_source_rx);

// Setup receive streamer
uhd::stream_args_t stream_args_rx("fc32", d_wire_rx); // complex

floats
std::vector<size_t> channel_nums; channel_nums.push_back(0); //
define channel!
stream_args_rx.channels = channel_nums;
d_rx_stream = d_usrp_tx->get_rx_stream(stream_args_rx);

//***** Misc *****//

// Setup rx_time pmt
d_time_key = pmt::string_to_symbol("rx_time");
d_srcid = pmt::string_to_symbol("usrp_echotimer");

// Setup thread priority
//uhd::set_thread_priority_safe(); // necessary? doesnt work...

// Sleep to get sync done
boost::this_thread::sleep(boost::posix_time::milliseconds(1000)); //

FIXME: necessary?
}

/*
 * Our virtual destructor.
 */
usrp_echotimer_cc_impl::~usrp_echotimer_cc_impl()
{
}

int
usrp_echotimer_cc_impl::calculate_output_stream_length(const

gr_vector_int &ninput_items)
{
int noutput_items = ninput_items[0];
return noutput_items ;
}

void
usrp_echotimer_cc_impl::set_num_delay_samps(int num_samps){
d_num_delay_samps = num_samps;

}

void
usrp_echotimer_cc_impl::set_rx_gain(float gain){
d_usrp_rx->set_rx_gain(gain);
}

void
usrp_echotimer_cc_impl::set_tx_gain(float gain){
d_usrp_tx->set_tx_gain(gain);
}

void
usrp_echotimer_cc_impl::send()
{
// Setup metadata for first package
    d_metadata_tx.start_of_burst = true;
d_metadata_tx.end_of_burst = false;
d_metadata_tx.has_time_spec = true;
d_metadata_tx.time_spec = d_time_now_tx+uhd::time_spec_t(d_wait_tx);

// Timespec needed?

// Send input buffer
size_t num_acc_samps = 0; // Number of accumulated samples
size_t num_tx_samps, total_num_samps;
total_num_samps = d_noutput_items_send;
// Data to USRP
num_tx_samps = d_tx_stream->send(d_in_send0, total_num_samps,

d_metadata_tx, total_num_samps/(float)d_samp_rate+d_timeout_tx);
num_tx_samps = d_tx_stream->send(d_in_send1, total_num_samps,
d_metadata_tx, total_num_samps/(float)d_samp_rate+d_timeout_tx);
// Get timeout
if (num_tx_samps < total_num_samps) std::cerr << “Send timeout…”
<< std::endl;

//send a mini EOB packet
d_metadata_tx.start_of_burst = false;
d_metadata_tx.end_of_burst = true;
d_metadata_tx.has_time_spec = false;
d_tx_stream->send("", 0, d_metadata_tx);
}

void
usrp_echotimer_cc_impl::receive()
{
// Setup RX streaming
size_t total_num_samps = d_noutput_items_recv;
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 = d_time_now_rx+uhd::time_spec_t(d_wait_rx);
d_rx_stream->issue_stream_cmd(stream_cmd);

size_t num_rx_samps;
// Receive a packet
num_rx_samps = d_rx_stream->recv(d_out_recv, total_num_samps,

d_metadata_rx, total_num_samps/(float)d_samp_rate+d_timeout_rx);

// Save timestamp
d_time_val = pmt::make_tuple
  (pmt::from_uint64(d_metadata_rx.time_spec.get_full_secs()),
   pmt::from_double(d_metadata_rx.time_spec.get_frac_secs()));

// Handle the error code
if (d_metadata_rx.error_code !=

uhd::rx_metadata_t::ERROR_CODE_NONE){
throw std::runtime_error(str(boost::format(“Receiver error %s”) %
d_metadata_rx.strerror()));
}

if (num_rx_samps < total_num_samps) std::cerr << "Receive timeout

before all samples received…" << std::endl;
}

int
usrp_echotimer_cc_impl::work (int noutput_items,
                   gr_vector_int &ninput_items,
                   gr_vector_const_void_star &input_items,
                   gr_vector_void_star &output_items)
{
    gr_complex *in0 = (gr_complex *) input_items[0]; // remove const

gr_complex *in1 = (gr_complex *) input_items[1];
gr_complex *out = (gr_complex *) output_items[0];

    // Set output items on packet length
    noutput_items = ninput_items[0]=ninput_items[1];

    // Resize output buffer
    if(d_out_buffer.size()!=noutput_items)

d_out_buffer.resize(noutput_items);

    // Get time from USRP TX
    d_time_now_tx = d_usrp_tx->get_time_now();
    d_time_now_rx = d_time_now_tx;

    // Send thread
    d_in_send0 = in0;
    d_in_send1 = in1;
    d_noutput_items_send = noutput_items;
    d_thread_send =

gr::thread::thread(boost::bind(&usrp_echotimer_cc_impl::send, this));

    // Receive thread
    d_out_recv = &d_out_buffer[0];
    d_noutput_items_recv = noutput_items;
    d_thread_recv =

gr::thread::thread(boost::bind(&usrp_echotimer_cc_impl::receive, this));

    // Wait for threads to complete
    d_thread_send.join();
    d_thread_recv.join();

    // Shift of number delay samples (fill with zeros)
    memcpy(out,&d_out_buffer[0]+d_num_delay_samps,(noutput_items-d_num_delay_samps)*sizeof(gr_complex));

// push buffer to output
memset(out+(noutput_items-d_num_delay_samps),0,d_num_delay_samps*sizeof(gr_complex));
// set zeros

    // Setup rx_time tag
    add_item_tag(0, nitems_written(0), d_time_key, d_time_val,

d_srcid);

    // Tell runtime system how many output items we produced.
    return noutput_items;
}

} /* namespace radar /
} /
namespace gr */

This is just a wish, but it would be nice if the set_start_time sequence
shown below could be added to the UHD Sink and Source blocks in GRC.
Seems generic enough (with the delay as a variable).

Ron

Hi Sanjoy,

On 06/28/2015 12:27 AM, Sanjoy Basak wrote:

However, this is not working for 2 X310s. I am not being able to make
time aligned Tx, Rx. I am using external reference. Would you please
suggest me some code/ modification for pyton file, so that the ports can
be time aligned.
Have you set both the clock and the time source to “external”
(set_clock_source, set_time_source), and told both USRPs to have the
same time at the next time pulse (set_time_next_pps)?

Best regards,
Marcus

Hi Marcus,
Thank you very much for the tips and suggestions. This is really
helpful.
You are right, I should not rely on Echotimer, rather I should try to
make one, based on my requirements.

First I tried the python code. This really worked for one X310 frontend
ports. I tried for 1Tx -2Rx and 2Tx – 1Rx. Those are time aligned with
the python code you suggested.

However, this is not working for 2 X310s. I am not being able to make
time aligned Tx, Rx. I am using external reference. Would you please
suggest me some code/ modification for pyton file, so that the ports can
be time aligned.

I also tried the code suggested in this link
http://usrp-users.ettus.narkive.com/6qvbyOIf/synchronizing-usrp-front-ends-via-gnu-radio

The code is actually to synchronize Tx front ends of 2 X310s.
I tried this for 1Tx - 1 Rx (Tx on usrp with gpsdo and Rx on usrp with
external reference). But this did not help to synchronize on time.

Best regards
Sanjoy

Hi Marcus,

I need help regarding the phase sync part that you mentioned in your
previous post here.

“There’s one thing that could use improvement in the echotimer code: If
the set_?x_freq() were done after the time and clock sources had been
set as a timed command (i.e. after calling set_command_time()), then the
SBX daughterboards would always have the same phase relationship after
tuning to the same frequency, which might be really handy in MIMO.”

This part I tried in python, however, I am not actually getting any
phase sync between the receive files. I am not really sure whether
defining freq after set_command_time() in python can really help.
However, please let me know what modification should I make or what
exactly I need to do.

I am putting the python code here that I am using right now for 2 usrps.
2 TXs are in one x310 (on gpsdo) and 2 RXs are on the other one
(external ref).
and the connection is TX-wire-30_dB_attenuator-wire-RX, I am taking
wired measurement. I am using 2.45 GHz freq.


    self.usrp_source0 = uhd.usrp_source(
      ",".join(("addr=172.xx.xx.73", "")),
      uhd.stream_args(
        cpu_format="fc32",
        channels=range(2),
      ),
    )

    self.usrp_sink0 = uhd.usrp_sink(
      ",".join(("addr=172.xx.xx.75", "")),
      uhd.stream_args(
        cpu_format="fc32",
        channels=range(2),
      ),
    )


    self.usrp_source0.set_clock_source("external", 0)
    self.usrp_source0.set_time_source("external", 0)
    self.usrp_source0.set_subdev_spec("A:0 B:0", 0)
    self.usrp_source0.set_time_unknown_pps(uhd.time_spec())
    self.usrp_source0.set_samp_rate(samp_rate)
    self.usrp_source0.set_gain(26, 0)
    self.usrp_source0.set_antenna("RX2", 0)
    self.usrp_source0.set_gain(26, 1)
    self.usrp_source0.set_antenna("RX2", 1)

    self.usrp_sink0.set_clock_source("gpsdo", 0)
    self.usrp_sink0.set_time_source("gpsdo", 0)
    self.usrp_sink0.set_subdev_spec("A:0 B:0", 0)
    self.usrp_sink0.set_time_unknown_pps(uhd.time_spec())
    self.usrp_sink0.set_samp_rate(samp_rate)
    self.usrp_sink0.set_gain(0, 0)
    self.usrp_sink0.set_antenna("TX/RX", 0)
    self.usrp_sink0.set_gain(0, 1)
    self.usrp_sink0.set_antenna("TX/RX", 1)

time.sleep(1)
print “receiver pps time:”
cmd_time = self.usrp_source0.get_time_last_pps()
print “transmitter pps time:”
cmd_time0 = self.usrp_sink0.get_time_last_pps()
real_seconds = uhd.time_spec_t.get_real_secs(cmd_time)
real_seconds0 = uhd.time_spec_t.get_real_secs(cmd_time0)

print real_seconds
print real_seconds0

self.usrp_source0.set_time_next_pps(uhd.time_spec_t(0.0))
self.usrp_sink0.set_time_next_pps(uhd.time_spec_t(0.0))

now = self.usrp_source0.get_time_now()
starttime = now + uhd.time_spec(1.5)
self.usrp_source0.set_start_time(starttime)
self.usrp_sink0.set_start_time(starttime)

    self.usrp_source0.set_center_freq(f, 0)
    self.usrp_source0.set_center_freq(f, 1)
    self.usrp_sink0.set_center_freq(f, 0)
    self.usrp_sink0.set_center_freq(f, 1)

    self.blocks_throttle_0_1 =

blocks.throttle(gr.sizeof_gr_complex1, samp_rate,True)
self.blocks_throttle_0_0_0 =
blocks.throttle(gr.sizeof_gr_complex
1, samp_rate,True)
self.blocks_throttle_0_0 =
blocks.throttle(gr.sizeof_gr_complex1, samp_rate,True)
self.blocks_throttle_0 = blocks.throttle(gr.sizeof_gr_complex
1,
samp_rate,True)
self.blocks_file_source_0_0 =
blocks.file_source(gr.sizeof_gr_complex1,
“/home/sanjoy/Desktop/new/siso with new preamble
3/20150603_siso_echotimer/floatgen.bin”, True)
self.blocks_file_source_0 =
blocks.file_source(gr.sizeof_gr_complex
1,
“/home/sanjoy/Desktop/new/siso with new preamble
3/20150603_siso_echotimer/floatgen.bin”, True)
self.blocks_file_sink_0_0 =
blocks.file_sink(gr.sizeof_gr_complex1,
“/home/sanjoy/Desktop/siso2.bin”, False)
self.blocks_file_sink_0_0.set_unbuffered(False)
self.blocks_file_sink_0 =
blocks.file_sink(gr.sizeof_gr_complex
1,
“/home/sanjoy/Desktop/siso1.bin”, False)
self.blocks_file_sink_0.set_unbuffered(False)

My system config is usrp X310, daughterboard SBX-120, uhd 3.9.

best regards
Sanjoy

Hi Marcus,
Thanks for the reply.
This worked today. Unfortunately set_command_time(),
clear_command_time() did not work well with my setup.
The Rx start point was varying with every initiation.

With the same code today I tried with set_start_time() and this worked
really well.
The time sync property with 2 X310 is the same like 1 X310.
Thanks a lot.

Best regards
Sanjoy

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