Hi Lorenzo,
The FFT block requires the number of samples per packet to exactly equal
the FFT size. When the graph commits, UHD will try to resolve a packet
size that all of the blocks are happy with. Perhaps if the FFT size is
2^11, this packet size may be bigger than the radio wants to deliver (or
bigger than the SPP you specified in the rx_streamer, I don't really know).
In my opinion, this is a really unnecessary limitation of the stock FFT
block. With relatively minor changes, this block would not need any linkage
between packet size and FFT length.
Rob
On Mon, Sep 12, 2022 at 8:20 PM Minutolo, Lorenzo <minut...@caltech.edu>
wrote:
> Hi All,
> I'm using UHD 4.2 to play around with RFNOC4. I successfully added an FFT
> block to the XG image of an X300, no static connections. uhd_usrp_probe
> returns as expected. I use the attached code to test it out.
> When I commit the graph I get the following error:
>
> Traceback (most recent call last):
> File "/home/lorenzo/test_rfnoc_fft.py", line 71, in <module>
> graph.commit()
> RuntimeError: ValueError: samples per package must not be smaller than
> atomic item size
>
> Digging a bit in the libraries I see that it originates from
> rfnoc_streamer.cpp, specifically:
> [...]
> if (ais.is_valid()) {
> const auto spp =
> this->rx_streamer_impl::get_max_num_samps();
> if (spp < ais.get()) {
> throw uhd::value_error("samples per package must not
> be smaller than atomic item size");
> }
> [...]
>
> Has someone encountered this error before?
>
> Thenks,
> Lorenzo
>
>
>
>
>
> Attached code:
>
> args = "addr=192.168.30.2"
> graph = uhd.rfnoc.RfnocGraph(args)
>
> radio_ID_A = uhd.rfnoc.BlockID(0, "Radio", 0);
> radio_block_A = graph.get_block(radio_ID_A);
> radio_ctrl_A = uhd.rfnoc.RadioControl(radio_block_A)
>
> set_freq = 300e6
> spp = 512
> radio_ctrl_A.set_tx_frequency(set_freq, 0)
> tx_freq = radio_ctrl_A.get_tx_frequency(0)
> radio_ctrl_A.set_rx_frequency(set_freq, 0)
> rx_freq = radio_ctrl_A.get_rx_frequency(0)
> print("Tuning is TX %.1f, RX: %.1f MHz" % (tx_freq/1e6,rx_freq/1e6 ) )
>
> radio_ctrl_A.set_properties(f'spp={spp}', 0)
> radio_ctrl_A.set_rx_antenna('RX2',0)
> radio_ctrl_A.set_rate(200e6)
>
>
> DDC_ID = graph.find_blocks("DDC")[0]
> DDC_block = graph.get_block(DDC_ID)
> DDC_control = uhd.rfnoc.DdcBlockControl(DDC_block)
> DDC_control.set_input_rate(200e6, 0)
> DDC_control.set_output_rate(5e6, 0)
>
> FFT_ID = graph.find_blocks("FFT")[0]
> FFT_block = graph.get_block(FFT_ID)
> FFT_control = uhd.rfnoc.FftBlockControl(FFT_block)
> FFT_control.set_length(spp)
> FFT_control.set_magnitude(uhd.libpyuhd.rfnoc.fft_magnitude.COMPLEX)
> FFT_control.set_direction(uhd.libpyuhd.rfnoc.fft_direction.FORWARD)
> FFT_control.set_shift_config(uhd.libpyuhd.rfnoc.fft_shift.REVERSE)
>
> stream_args = uhd.usrp.StreamArgs('fc32','sc16')
> stream_args.args = 'spp='+str(spp)
> rx_stream = graph.create_rx_streamer(1, stream_args)
>
> graph.connect(
> radio_ID_A,0,
> DDC_ID,0,
> False
> )
> graph.connect(
> DDC_ID,0,
> FFT_ID,0,
> False
> )
>
> graph.connect(
> FFT_ID,0,
> rx_stream,0
> )
>
> graph.commit()
>
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