Re: [Discuss-gnuradio] packets to the usrp and loopback

[Brian Padalino]

On 4/20/07, Thibaud Hottelier <address@hidden> wrote:
> Yes, it's this module. Any suggestion for a better name?

According to your diagram here:
 http://gnuradio.org/trac/wiki/UsrpTxModifications

Maybe we should have a tx_usb_fifo, tx_usb_fifo_reader, tx_chan_fifo,
tx_chan_fifo reader, tx_cmd_fifo_reader (the tx_chan_fifo and
tx_cmd_fifo are essentially the same thing, but the tx_cmd_fifo_reader
should figure out I2C, SPI, and other settings that may go down the
command FIFO).

Putting all of this within an mblock_processing module would be nice.

A potential hierarchy:
- mblock_processing
 - tx_usb_fifo
 - tx_usb_fifo_reader
 - tx_chan_fifo
 - tx_chan_fifo_reader
 - tx_cmd_fifo_reader

You currently have it where the FIFOs are sitting inside of the
readers, which I could be OK with - but would prefer if the FIFOs were
separate.

Since we're just talking data and no command yet, I'll limit it to
that, but we should be aware of all the things the tx_cmd_fifo_reader
should be able to parse and do.  Specifically, everything listed here:
 
http://gnuradio.org/trac/browser/gnuradio/branches/features/inband-usb/usrp/doc/inband-signaling-usb

> I have not really understood this strobing thing. From the current
> tx_buffer code, I understood that I can independently feed one sample
> per channel between each strobe. But you just said they were not
> independent so I am confused...

On the input side of the interpolating CIC filter, we input samples at
a rate of 1/rate.  On the output side of the interpolating CIC filter,
samples come out every clock cycle.  It's just the rate at which the
samples are supposed to be fed into the interpolating CIC filters to
get upconverted.

In the current design, everything is set to a single interpolation
rate and a single decimation rate for all TX or RX channels.  In the
mblock design, we want to be able to independently control the
bandwidth and rates of each of the complex channels.  This allows for
all sorts of interesting and different schemes to work.

Does that make sense?

Brian