Re: [Discuss-gnuradio] USRP packet parsing

[Thibaud Hottelier]

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
> header.
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,
> correct?

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?

> Brian

Thibaud