Re: [Discuss-gnuradio] Extending UHD USRP Sink in out-of-tree module

[Josh Blum]

On 04/12/2013 07:45 PM, Sean Nowlan wrote:
> I mean to set those controls dynamically based on incoming stream
> tags, similar to the way burst tags work. For instance I designed a
> tx_gain tag that gets read by uhd_usrp_sink and sets the gain using
> set_command_time. I just wanted to know the easiest way to move this
> modified sink to an OIT of tree module, even though I'll be
> duplicating most of the gr-uhd code to do it.
> 

I see. Sounds like it doesn't fit well. I wouldn't recommend tags or for
that matter modifying the source/sink block. Since 1) the control is
async to the data anyway, 2) the control would get delayed by the data
pipeline, 3) it wouldn't make sense in the case of the source block.

Rather I would create another block which opens a usrp session and
accepts control messages to act on. I happen to have one in the works,
but its not ready yet.

Also, if it fit well, you would FWIW, open the usrp device session in
your control block/IP, whatever that may be, and talk directly to it.
That may be convenient. A lot less to maintain out of tree in either
case anyway.

-josh

> Josh Blum <address@hidden> wrote:
> 
>> 
>> 
>> On 04/12/2013 07:00 PM, Sean Nowlan wrote:
>>> I want to add some functionality to gr_uhd_usrp_sink to change
>>> frontend gain and tune the DDC. I've achieved part of this in the
>>> past by
>> 
>> Hooks are already exposed to set individual gain element, or
>> individual parts of the tuning chain. The later is even available
>> in GRC. What specifically is missing?
>> 
>>> modifying the files directly in gnuradio/gr-uhd, but that's an
>>> imprecise way to do it. Would you recommend I:
>>> 
>>> 1) copy the code from the gnuradio tree to my out-of-tree module,
>>> change namespaces, etc. and add my functionality? 2) create my
>>> own private uhd_usrp_sink_impl that extends gnuradio's 
>>> uhd_usrp_sink and add my functionality there? 3) something else?
>>> 
>> 
>> If its using stock FPGA images and all, branch off of the gnuradio 
>> maint, contribute the changes back.
>> 
>>> I remember reading something on this list from somebody who
>>> rolled their own usrp wrapper. Any hints?
>>> 
>> 
>> That turned out to be an attempt to set gain from the work
>> function based off of some older USRP1 app that did the same. In
>> any case, it actually wasnt needed.
>> 
>> -josh
>> 
>>> Thanks,
>>> 
>>> Sean
>>> 
>>> _______________________________________________ Discuss-gnuradio
>>> mailing list address@hidden 
>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>> 
>> _______________________________________________ Discuss-gnuradio
>> mailing list address@hidden 
>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio