Re: [Discuss-gnuradio] USRP packet parsing

[Brian Padalino]

On 3/24/07, Thibaud Hottelier <address@hidden> wrote:
> I updated the wiki paged and added state machines.
> (http://gnuradio.org/trac/wiki/UsrpTxModifications)

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
header.

> 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,
correct?

> - When a packet is outdated I still have to walk though it to empty to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.

> Thibaud

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.

Brian