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Re: [Discuss-gnuradio] USRP packet parsing

From: Brian Padalino
Subject: Re: [Discuss-gnuradio] USRP packet parsing
Date: Sat, 24 Mar 2007 17:59:06 -0400

On 3/24/07, Thibaud Hottelier <address@hidden> wrote:
I updated the wiki paged and added state machines.

A comment with the USB Block - I believe all the processing going into
the USB FIFO is done within the FX2.  Moreover, i don't know why
you're keeping the byte_count around - it's coming in with the packet

Here are the issues still unresolved that I am aware of:

- Are the overrun/underrun flag per channel or global? From which fifo
should they be generated?

Each channel should be responsibile for returning each individual
status back up to the host.  With that given, I believe the messages
should be sent up and identified as stating "TX Channel 0" or "RX
Channel 1" is having over or under runs.  That would be helpful,

- When a packet is outdated I still have to walk though it to empty to
skip it. This can be resolved by using a RAM block rather than a fifo
for the N chanX_fifo be will require more coordination between the USB
block and the data block.

Being able to skip over an entire packet if the over or underrun
happens, is extremely helpful and should be implemented.  We can have
a modified FIFO possibly with a way to "skip" a specific number of
packets?  That would be interesting and easily implementable within
your state machines.

- Now I am assuming that the samples are 16bits interleaved, how will
the sample format chosen by the user be reported to the FPGA?

There is a command that is sent down to the FPGA and can be set in a
mux.  The "format" should be passed into the processing FSM and
handled there.  It's a good question - no real idea right now how to
handle this.


Good job so far.  It's probably just me, but those FSMs just seem a
little busy and a little confusing.  I'll figure them out soon enough.


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