Re: [Discuss-gnuradio] inband timestamp issues

[Brian Padalino]

On Thu, Aug 21, 2008 at 3:11 AM, Eric Schneider
<address@hidden> wrote:
> Hi all,  I'd really like to help with this.  I've been pouring over the
> design (usrp_inband_usb), so my brain is a little mushy at the moment,
> hopefully I'm not totally off track here.
>
> 1. Is it true that there are N RX Sample FIFOs?  It seems that the channels
> are already muxed by the time they get to the packet_builder, no?

The packet builder itself actually does the muxing:

    
http://www.gnuradio.org/trac/browser/gnuradio/trunk/usrp/fpga/inband_lib/packet_builder.v

The N RX sample FIFOs are built here:

    
http://www.gnuradio.org/trac/browser/gnuradio/trunk/usrp/fpga/inband_lib/rx_buffer_inband.v#L168

> 2. Can we just subtract the FIFO size (usedw?) from the timestamp in the
> packet builder?

Sure, but what for?  I suppose I am not sure what this is addressing?

> 3. When checking timestamps for expired command/data packets, is an
> overflow/wraparound on the timestamp_clock handled?  (ref cmd_reader.v:107,
> chan_fifo_reader.v:145)

I don't think it's explicitly being taken care of, but I am also not
sure if the logic just ends up working out.  This should probably be
looked at and a testbench written.

> 4. I wholeheartedly agree that it would be nice to have a "read N samples at
> time T command".
>
> --ets

Brian