Forum: GNU Radio [InBand]Rx side design

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F5783e57f96492325e7d1837fcfdcaf9?d=identicon&s=25 Thibaud Hottelier (Guest)
on 2007-06-11 19:13
(Received via mailing list)
Hello,

Here is a diagram of the Rx side.
http://www.andrew.cmu.edu/user/thottelt/rx.png

I plan to use a fifo to cross clock domains because it's simpler than a
delay cell. Samples and commands will be stored in dual port fifos (one
per channel) A reader will poll them: if there are samples or commands,
push one single packet then poll next fifo. This should give a fair
share of the USB bandwidth to all channels/commands. I think I will be
able to reuse most of the code in the current rx_buffer that deals with
the FX2 DMA engine and the samples format, so the only task left is
building the packet itself.

Any comments, concerns ?

Thanks,
Thibaud
F5783e57f96492325e7d1837fcfdcaf9?d=identicon&s=25 Thibaud Hottelier (Guest)
on 2007-06-12 00:33
(Received via mailing list)
Something surprised me in the current rx_buffer code: It seems that if
samples are received from different rx_chains at the same time, they
will be mixed in the next USB packet toward the host. Has the host a way
to separate them? Shall I keep this behaviour or separate samples by
channel when USB packets are built?

Thanks,
Thibaud
3596cfe1d579c65b9babd35e8787977c?d=identicon&s=25 Matt Ettus (Guest)
on 2007-06-12 00:48
(Received via mailing list)
Thibaud Hottelier wrote:
> Something surprised me in the current rx_buffer code: It seems that if
> samples are received from different rx_chains at the same time, they
> will be mixed in the next USB packet toward the host. Has the host a way
> to separate them? Shall I keep this behaviour or separate samples by
> channel when USB packets are built?
>

The standard USRP code interleaves samples from the different streams.
The host side code does the separation, although it is not always
necessary.  For the inband work we should keep them separate, at least
for now.

Matt
745d8202ef5a58c1058d0e5395a78f9c?d=identicon&s=25 Eric Blossom (Guest)
on 2007-06-12 01:33
(Received via mailing list)
On Mon, Jun 11, 2007 at 06:32:19PM -0400, Thibaud Hottelier wrote:
> Something surprised me in the current rx_buffer code: It seems that if
> samples are received from different rx_chains at the same time, they
> will be mixed in the next USB packet toward the host. Has the host a way
> to separate them? Shall I keep this behaviour or separate samples by
> channel when USB packets are built?
>
> Thanks,
> Thibaud

Separate by channels.  We'll eventually define a subchannel
abstraction that will interleave multiple DDC outputs into a single
channel.

Eric
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