Re: Endian-ness of USRP x410 device

Thankyou Marcus and Martin for the replies. Ok probably that's why I can't send it to the usrp-users.

As you suggested, I looked at some other Rfnoc blocks in the repo but I couldn't really find anything in particular. Maybe I am looking at it wrong. So, in the meantime, I setup an ILA (again thanks Martin for the one reply where you detailed out how to set it up to another user), and I see that the data coming from the nocshell (m_in_axis_tdata) is a unrecognizable to the data I sent via TX streamer in gnuradio. I added some debug prints along the way - one on the block preceding the TX streamer, in the send() (in TX streamer in UHD) and ILA in the FPGA. I also checked if its just the IQ change that is mentioned in the Rnoc Spec pdf, but thats not it either.

For my configuration, I use item_w=32, chdr_w=64, cpu_format=sc16 and otw=sc16. So theoretically this shouldnt do any other conversions right? Or maybe I am missing something?

-J

On Thu, 27 Nov 2025 at 12:00, Martin Braun <martin.braun@ettus.com> wrote:

Hey Jons,

our mailing list server is having some issues. Our maintainer knows about this, but I can't give you a timeline for when it'll be up again.

Like Marcus says, don't worry about the network endianness. We have a bunch of things going on to flip bytes around (among other things, it saves us some CPU load when receiving data), but you need to worry about the Noc-Shell interface. I recommend looking at some of our existing blocks as examples.

--M

On Wed, Nov 26, 2025 at 4:01 PM Marcus Müller <mmueller@gnuradio.org> wrote:

Hi Jons,

On 2025-11-26 9:17 AM, Jons wrote:
> Hi all,
> This is a specific question about USRP devices and I am posting it here because I am
> unable to send it to the usrp-users mail chain.

Uh, I'm not with Ettus anymore, but that's no good. All you should need to do is send an
email from your email address to usrp-users-join@lists.ettus.com ; after you've gotten a
confirmation email and confirmed, you should be able to post there.

> I am trying to integrate a custom noc
> block into the x410 device and when going through the email archive and a doc in the
> github repo I saw that the OTW data transmission is in Big Endian.

I'll go with: that's a time-honoured tradition :D

> Can someone help me out
> in understanding how it will affect a noc block?

Not at all – you're not interfacing with the network directly, but with your nocshell, and
your verilog module / VHDL arch sees the sample data as sample-wide array (CHDR_W is the
naming convention for the width parameter, if you want to look through the source code of
Ettus' blocks), typically.

Best,
Marcus