Thomas, Upon further investigation, we may be running up to a practical limit of a single CHDR interface rather than an issue with your code. A single replay block servicing two radios will have a max (theoretical) rate of 187.5 MSPS on either channel. This means that you might be able to squeeze full rate out on 2 channels with an MCR of 184.32, but that's cutting it pretty close. Sounds like 2 channels at 200 MSPS with a replay setup will require 2 replay blocks serving each channel independently. If you end up trying either of the above out, I'd be curious to know what results you observe.
Sam Reiter Ettus Research On Fri, Dec 6, 2019 at 2:38 PM Sam Reiter <sam.rei...@ettus.com> wrote: > Thomas, > > I'd need to set it up on my end, but I believe you can TX two distinct > waveforms from a single replay block instance. You'd need to make sure that > your adding your data to the buffer in separate locations and at an address > that is a multiple of 8 bytes (which it looks like you're doing from the > above snippets). Are you seeing continuous underruns, or just a handful at > the beginning on the run? Does your duplicated code also use: > > replay_ctrl->get_record_fullness > > on both channels before kicking off the stream start? > > Sam Reiter > Ettus Research > > On Wed, Dec 4, 2019 at 3:48 AM Thomas Harder via USRP-users < > usrp-users@lists.ettus.com> wrote: > >> Hello everyone, >> >> Is it possible to transmit two different waveforms on the two channels of >> the USRP X310 with the two UBX-160 daughterboards? >> >> I want to transmit two different waveforms simultaneous (synchronized ) >> on the two channels of the USRP with the full sample rate of 200 MS/s. I >> tried already to do it with a dual 10Gbit-ethernet connection and I seemed >> to be limited by my computer. Now I am trying to do it with the replay >> block. >> >> >> >> I built the FPGA image with one Replay block as described in >> https://kb.ettus.com/Using_the_RFNoC_Replay_Block to run the example >> “replay_samples_from_file” and it is working fine if I transmit just on one >> channel. Now I was modifying the code by connecting the replay block to >> both channels: >> >> >> replay_graph->connect(replay_ctrl->get_block_id(),replay_chan,tx_blockid,tx_chan,replay_spp); >> >> >> replay_graph->connect(replay_ctrl->get_block_id(),replay_chan1,tx_blockid1,tx_chan,replay_spp); >> >> >> >> and writing the same waveform into another region of the DRAM-buffer: >> >> replay_ctrl->config_record(0,words_to_replay*replay_word_size, >> replay_chan); >> >> replay_ctrl->config_record(20000,words_to_replay*replay_word_size, >> replay_chan1); >> >> and >> >> replay_ctrl->config_play(0,words_to_replay*replay_word_size, replay_chan); >> >> replay_ctrl->config_play(20000,words_to_replay*replay_word_size, >> replay_chan1); >> >> >> >> where >> >> words_to_replay*replay_word_size=16000 >> >> replay_chan=0 >> >> replay_chan1=1 >> >> tx_blockid=0/Radio_0 >> >> tx_blockid=0/Radio_1 >> >> >> >> then I stream my waveforms to the replay block as defined in the example >> and I start to replay the data: >> >> replay_ctrl->issue_stream_cmd(stream_cmd, replay_chan); >> >> replay_ctrl->issue_stream_cmd(stream_cmd, replay_chan1); >> >> >> >> It works but with plenty of Underflows!! >> >> >> >> So what does it mean when it says in the manual: >> >> “Note that the record and playback buffers do not need to the same, >> allowing a single Replay block to both record and playback to different >> regions of memory* simultaneously*.” >> >> (https://kb.ettus.com/Using_the_RFNoC_Replay_Block)? >> >> >> >> Because in the manual it says also: >> >> “The replay block has the following features: One input and *one* output” >> >> ( >> https://files.ettus.com/manual/classuhd_1_1rfnoc_1_1replay__block__ctrl.html >> ) >> >> >> >> So if the replay block has just one output why does it have two channels >> connected to it (replay_chan= 0 and 1)? >> >> >> >> If one replay block can just stream to one channel at the same time, can >> I implement easily a second replay block in the FPGA to stream on the two >> channels of my USRP two different waveforms simultaneously? >> >> >> >> Thank you, >> >> Thomas >> >> >> >> >> >> >> >> >> >> >> _______________________________________________ >> USRP-users mailing list >> USRP-users@lists.ettus.com >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com >> >
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