Hi Xingjian, If I understood your problem correctly, you are expecting two equal streams to arrive at the same time on the output, but you have an AXI Crossbar in the middle. This is a packet-based router, so it is hard to predict its behavior timing-wise, and I don't think this would be the right approach even if you could. I recommend you should make use of the timestamp in CHDR headers, and instruct your radio_cores to output your samples at the same time that way.
Regards, Leo. On Mon, Apr 8, 2019 at 11:52 AM Xingjian Chen via USRP-users <usrp-users@lists.ettus.com> wrote: > > Dear All, > I am doing FPGA debugging with an E312. I have two exactly same signal > generation RFNOC modules run simultaneously. The waveform is triggered by a > reference clock generated in Verilog at the same time. What I found is that > when the waveform went from RFNOC module to noc_block_radio_core in > tx_control_gen3.v, the initial phase relative to the reference clock changed, > the waveform in one tx channel is delayed by half cycle than the other tx > channel. And when I tested and recorded one of the channels' timing by > chipscope ila tool. There is a roughly 50% chance that I get a right initial > phase and 50% chance that I get the half cycle delayed version. > I think this is due to competition between two tx modules when both were > sending packets to the bus, the AXI Wrapper or the NOC shell randomly picked > one of them to go first and then alternating the data transferring. > What I would like to do is to transmit two fixed initial phase waveforms > relative to a reference clock. Could you please give me some hint that how to > deal with this problem? > I think maybe I can make two different RFNOC modules such that the first tx > module always waiting for the second module at the starting moment. Maybe I > should play with the "s_axis_data_tvalid". But I don't know how to set this > up with AXI Wrapper and NOC shell. Thank you for your help! > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com -- Leandro Echevarría _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
