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Re: [Discuss-gnuradio] USRP packet parsing

From: Thibaud Hottelier
Subject: Re: [Discuss-gnuradio] USRP packet parsing
Date: Sun, 25 Mar 2007 14:52:01 -0400
User-agent: Thunderbird 2.0b2 (X11/20070319)

Brian Padalino wrote:
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

Are you sure? I thought the FX2 was only buffering the packets, and is communicating with the fpga through the 16 bits wide usb_data bus.

Byte_count is how many byte from the current packet have been already received. I need it to skip the padding and to know when the packet is completely stored in usb_fifo, because packets are processed only when they are complete (that's why I also keep track of the number of complete packet in usb_fifo).

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,

Eric, suggested to just OR all the chanX_fifo_{underrun, overrun} and consider the E and S flags are per channel. I think it's a good compromise between complexity and accuracy. What about you?

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.

Yes, I think that adding the skip functionality to the Altera fifo is easiest solution.

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.

Ok, so it won't modify the state machines, it will just add a switch statement when the samples are sent to txX_chain.

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.

Yes, I made them with Dia, that probably not the best tool for that. If you know any better tool that works on Linux, let me know. I drew the conditions and actions associated with each transition, is that too much?



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