Dear all,
I would like to periodically send a frame with an USRP X310 (frame
length: 320 samples, rate: 20 MS/s, period: 1-500 ms). However, I
struggle to find the best way to implement it. What I have tried so far:
1. Append zeros to the frame to reach the expected period. However,
this consumes too much bandwidth due to the zeros.
2. Use tx_streamer->send() with a tx_metadata_t.time_spec and
tx_streamer->recv_async_msg(). Using that, only the frame is sent,
saving most of the bandwidth. However, with small periods, it tends to
print some 'L'.
3. Buffer a batch of send request on the USRP, then wait a specific
time (using eg. recv_async_msg() until the returned metadata contains
the penultimate time_spec (I expect that the time_spec returned is the
one specified in the send metadata)) and redo. The issue is that I was
not able to find the buffer size (is it related to the
tx_streamer->get_max_num_samps()?). I would like to fill the buffer
without overflow.
I was hoping that I could save the frame in an USRP's memory, and then
ask it to periodically send the frame with a specific period. Is it
possible?
Here is an example of (2):
template <typename samp_type>
void send_from_file(const uhd::usrp::multi_usrp::sptr &usrp,
uhd::tx_streamer::sptr tx_stream, const std::string&
file,
const double period)
{
size_t data_size = get_file_size<samp_type>(file);
std::ifstream infile(file, std::ifstream::binary);
std::vector<samp_type> buff(data_size);
infile.read(reinterpret_cast<char*>(buff.data()),
(std::streamsize)(buff.size()*sizeof(samp_type)));
infile.close();
size_t num_tx_samps = buff.size();
std::cout << file << " " << buff[0] << " " << num_tx_samps << std::endl;
uhd::tx_metadata_t md;
md.start_of_burst = true;
md.end_of_burst = true;
md.has_time_spec = true;
md.time_spec = usrp->get_time_last_pps()+5.;
double timeout = md.time_spec.get_real_secs();
uhd::async_metadata_t md_status;
while (not stop_signal_called) {
tx_stream->send(&buff.front(), num_tx_samps, md);
if (tx_stream->recv_async_msg(md_status, timeout)) {
if (md_status.event_code !=
uhd::async_metadata_t::event_code_t::EVENT_CODE_BURST_ACK) {
std::cerr << "Error: " << md_status.event_code <<
std::endl;
exit(EXIT_FAILURE);
}
} else {
std::cerr << "timeout before sent" << std::endl;
exit(EXIT_FAILURE);
}
timeout = 0.1;
md.time_spec += period;
}
}
Best Regards,
Cédric
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