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Re: [Discuss-gnuradio] usrp usb buffer minimum requirement

From: Mattias Kjellsson
Subject: Re: [Discuss-gnuradio] usrp usb buffer minimum requirement
Date: Thu, 27 Aug 2009 12:46:13 +0200
User-agent: Thunderbird (X11/20090817)

adib_sairi wrote:
Dear All,
As i being experimenting with USRP and GNU Radio, i notice that some of the
last packet of my data that i receive is keep inside the USB buffer. this
data will be flush out to my PC only if i transmit (receive) new data. i
believe that this is due to the minimum byte data needed by the USB buffer
(fusb_block_size - 512). so even though there is some receive packet inside
the USRP, it won't be send to the PC until it is a group of 512 byte of
data. am i correct?

so at the transmitter, i should send an extra 512byte of data for each of my
last packet that is transmitted for one session..
I think there is more to it than just the usrp and usb. Today I have been working on a test- case
where I have the following flow- graph (in c++ if that might matter)

file_sink-> "some blocks" -> file_sink

If the file- sink was not exactly 8k = 8192 bytes large the whole flow- graph gave unpredictable output in terms of size of the output. Note that I used "repeat = false" in the file- source.

I'm not sure if it's the number of items in the source or the size of it, since it in my case is the same (using a bit- file- source).

Hope this helps (and that someone else has more input)

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