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

[Mattias Kjellsson]

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)
//Mattias