Re: [Discuss-gnuradio] Question regarding usrp2_basic.cc

[Eric Blossom]

On Thu, Jul 03, 2008 at 08:23:16PM +0200, Mattias Kjellsson wrote:
> Hi,
>
> I have been browsing the sources for the usrp2, so that I'm familiar enough 
> with the code when the new usrp2 comes. I have a million questions 
> regarding it, but there is one simple one for starters. At line 70 in my 
> usrp_basic.cc (svn-rev 8510), i have the following line of code:
>
> #define MAX_PKTLEN 1512 //biggest thing USRP2 can swallow
>                                               // (14-byte ethernet hdr + 
> 1500 byte payload)
>
> My question is; Is there something I have missed regarding the packets and 
> their format, is this a typo, is it something that everybody else knows 
> (for instance -"you always have to pad the packets with one byte" or 
> similar), or something completely  different than the above suggestions?
>
> Cheers
> //Mattias Kjellsson

Oh, you want to know about the missing 2 bytes ;)

The reason it's 1512 and not 1514 is that the USRP2 always writes
32-bit words to the ethernet.

Eric