I suspect your logic isn't processing packets correctly. For example, maybe the sequence number is wrong on the output packets, or some other header information is incorrect. Or maybe your AXI-Stream handshake logic is wrong, causing you to miss samples. Or maybe TLAST isn't being asserted on the correct sample. Something like that. It's hard to say. But the `D` could mean simply that the packets going back to your host computer are incorrectly constructed.
Wade On Wed, Jul 5, 2023 at 12:16 AM Philipp Niedermayer <[email protected]> wrote: > Dear all, > > we are working on a custom OOT RFNoC Block implementation [1] on a USRP > X310 and are facing data throughput bottlenecks. > > The DSP is controlled via GNU Radio / UHD like this: > Signal Source -> RFNoC TX Streamer -> custom OOT block -> RFNoC RX > Streamer -> QT GUI Time Sink > > When running the flow graph we get a lot of "DDDD" printed to the console, > i.e. package drop due to buffer overflow. Adding a GNU Radio "Probe rate" > block shows that the sampling rate before the TX Streamer is 200kSps as > desired. However, behind the RX Streamer, the sampling rate is only 64 Sps > (!). > > When bypassing our custom VHDL implementation in the OOT Block (i.e. > assigning all s_out_axis_t* to respective m_in_axis_t*) the flow graph > works as expected, so the RFNoC part alone works just fine. > > The VHDL implementation requires some 100 clock cycles for a sample to > propagate. But since we use the 200MHz clock, achieving sampling rates of > 200kSps should not be an issue. The custom OOT block also has an option for > interpolation (i.e. increasing sampling rate), but the behaviour is the > same even for interpolation=1. > > Do you have some hints on how to improve performance? We have already > tried to > - Increase the payload FIFO depth from 32 to 128 > - Try both, the context-payload and the data AXI-Stream interface > - Assert tlast on every sample to reduce packages size > > Some things we have considered but are not sure about: > - MTU size > - Package size > > Thanks for taking the time to share your ideas > Philipp, Jernej, Blaž > > > [1] > https://git.gsi.de/p.niedermayer/exciter/-/blob/f02ee94ad3358fff313fc14a1a8d8494ad68d8ab/rfnoc-beam_exciter/fpga/rfnoc_block_feedback_controller/rfnoc_block_feedback_controller.v#L419 > > > _______________________________________________ > USRP-users mailing list -- [email protected] > To unsubscribe send an email to [email protected] >
_______________________________________________ USRP-users mailing list -- [email protected] To unsubscribe send an email to [email protected]
