Re: [Discuss-gnuradio] User experience with E1x0 boards

[Philip Balister]

On 05/04/2011 02:03 AM, Alexander Chemeris wrote:
> On Wed, May 4, 2011 at 02:33, Josh Blum<address@hidden>  wrote:
> > > 4) Be sure to tell UHD you want integer samples. I'm thinking even then
> > > UHD has to swap IQ for historical reasons. (Josh, help?)
> >
> > There is a copy-conversion operation between kernel buffer memory and
> > user memory. If the user requests complex shorts, I believe the
> > conversion is the equivalent of a 16 bit integer pair swapping. This
> > routine could be replaced with NEON intrinsics pretty easily.
>
> Ugh. Could you please point us to this code so we can disable it? We
> don't need to convert data in real-time, and if we can avoid copying
> it would be great help too. We need to capture raw data to RAM with
> maximum possible throughput and then process it in offline mode.

I would do it in the FPGA. It is not a huge deal, but at the rates you 
want, every little bit helps.

The floating point translation uses a NEON vrev instruction to do the 
swapping, but I think the swap is done in C++ for the int case. (Based 
on a quick look last night).

Philip