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
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