Would it make sense to separate into 2 threads where one thread sends the
tuning commands and the other sends the Tx samples?
Rob
On Mon, Jun 6, 2022 at 5:12 PM <ri28...@mit.edu> wrote:
> I modified the three files described above, changing the CMD_FIFO_SIZE
> parameter in dds_timed.v and axi_tag_time.v, and FIFO_SIZE in ddc.v. In all
> cases I attempted to adjust to 20, but that used too much BRAM and I
> instead tried 10, which successfully built.
>
>
> I loaded the bitfile onto an x310, and ran the following code snippet to
> test:
>
> uhd::time_spec_t initial_lat(1.0);
> uhd::time_spec_t cmd_time(0.0);
> // Amount of time to increment on each iteration
> uhd::time_spec_t schedule_increment(0, FREQ_SCHEDULE_WINDOW_TICK,
> CLOCK_RATE);
> uhd::tx_metadata_t md;
> md.has_time_spec = true;
> md.start_of_burst = true;
> md.end_of_burst = true;
>
> global_usrp_time = usrp->get_time_now();
> // Assume the first packet arrives some time before it is actually sent
> cmd_time = global_usrp_time + initial_lat;
>
> for (int i = 0; i < queue_size; i++)
> {
> // Transmit
> md.time_spec = cmd_time;
> tx_streamer->send(ppayload, nsamples, md);
> cmd_time += schedule_increment;
>
> // Hop at a scheduled time
> usrp->set_command_time(cmd_time);
> usrp->set_tx_freq(tune_request.getNextTuneRequest());
> }
>
> The idea is that I schedule approximately one second in the future a
> number of transmits and hops spaced ~200 us apart. If the USRP has enough
> timed command slots in both the digital resampling chain and the transmit
> chain, this will work fine.
>
> Running this code with queue_size = 5 against the base x310 image works,
> but produces a bunch of late Ls to stdout when queue_size = 6. My image
> which I built with the above parameter modifications has the same behavior
> as the base image, failing at queue_size = 6.
>
> Is there another FIFO somewhere I need to grow?
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