Re: Here's how to get the N321's LO sharing to work in GNURadio 3.9 with UHD4.1.0.5

[Paul Atreides]

Hey Daniel. 
Glad you like it. The functionality is there for now, but I have some 
reservations about recommending this for upstream. 
TLDR: more work probly needs to be done for the changes to be stable. 

My suggestions/concerns on upstream changes are as follows:

1) If the file system naming convention changes in new versions of UHD my 
function will break in gr-uhd since the file system path is hardcoded. As 
you’ve probly noticed UHD abstracts the various fs paths into variables so 
changes to the fs are transparent to the API. 

2) my changes need to follow the naming convention and abstraction of gr-uhd. 
For example, any functions that exist for both TX and RX are put in the common 
block and then the same function is used for TX/RX in either sink or source 
blocks respectively. 

3) I think adding LO distribution as a parameter in the GRC block would also be 
necessary to follow have “GNURadio citizenship”. 

I honestly like the direction of your solution more because it follows the API 
interplay that’s already in place between UHD and gr-UHD. Unfortunately, as you 
pointed out it would require the modifications to be a upstreamed for both UHD 
and gr-uhd. 

I think I could handle the gr-uhd part if the UHD side gets done. 
Does anyone from Ettus think this would be a valuable addition? Could we get 
some help on adding a convenience function for LO distribution board enable to 
the UHD API?

<end transmission>

> On Jan 29, 2022, at 04:46, Daniel Estévez <daniel@destevez.net> wrote:
> 
> Hi,
> 
> Thanks! That seems very nice. Could we try upstreaming this? I don't see any 
> obvious drawbacks to having this in-tree, particularly since your approach 
> doesn't require modifying UHD.
> 
> Best,
> Daniel.
> 
>> El 28/1/22 a las 23:55, Paul Atreides escribió:
>> Currently there's no way to use LO sharing with the N321 in gr-uhd.
>> The N321 uses an RF Distribution board which has port terminations that need 
>> to be switched to active outputs when the LO is exported. This isn't 
>> accessible in gr-uhd.
>> In order to access the LO distribution enable commands shown here:
>> https://kb.ettus.com/USRP_N320/N321_LO_Distribution#UHD_LO_Distribution_Commands
>>  
>> <https://kb.ettus.com/USRP_N320/N321_LO_Distribution#UHD_LO_Distribution_Commands>
>> a function needs to be added to gr-uhd
>> All this code below is taken from here:
>> https://github.com/daniestevez/uhd/commit/0a6da1a3fd5839b862cac740ed702923ed21b096
>>  
>> <https://github.com/daniestevez/uhd/commit/0a6da1a3fd5839b862cac740ed702923ed21b096>
>> https://github.com/daniestevez/gnuradio/commit/f9909bade86045f379f83001de27317cc261807f
>>  
>> <https://github.com/daniestevez/gnuradio/commit/f9909bade86045f379f83001de27317cc261807f>
>> with the rx switched for tx and source switched for sink
>> i also did not modify any UHD code making this a fix that requires ONLY 
>> modifying gr-uhd
>> usrp_sink_impl.cc
>> voidusrp_sink_impl::set_tx_lo_dist(boolenabled,
>> conststd::string&name,
>> size_tchan)
>> {
>> #ifdefUHD_USRP_MULTI_USRP_TX_LO_CONFIG_API
>> _dev->get_tree()->access<bool>("/blocks/0/Radio#0/dboard/tx_frontends/0/los/lo1/lo_distribution"/::uhd::fs_path(name)
>>  /"export").set(enabled);
>> #else
>> throwstd::runtime_error("not implemented in this version");
>> #endif
>> }
>> usrp_sink_impl.h
>> voidset_tx_lo_dist(boolenabled,
>> conststd::string&name, size_tchan= 0) override;
>> usrp_sink.h
>> virtualvoidset_tx_lo_dist(boolenabled, conststd::string&name, size_tchan=0) 
>> = 0;
>> usrp_sink_python.cc
>> .def("set_tx_lo_dist",
>> &usrp_sink::set_tx_lo_dist,
>> py::arg("enabled"),
>> py::arg("name"),
>> py::arg("chan") =0,
>> D(usrp_sink, set_tx_lo_dist))
>> usrp_sink_pydoc_template.h
>> staticconstchar* __doc_gr_uhd_usrp_sink_set_tx_lo_dist= R"doc()doc";
>> Assuming the sink block is "usrp_sink_0"
>> snippet_0 code
>> 'Main-After Init'
>> # Turn on the ports
>> self.usrp_sink_0.set_tx_lo_dist(True,"LO_OUT_0",0)
>> # repeat the above for all ports needed "LO_OUT_<N>"
>> snippet_1
>> 'Main-After Stop'
>> # Turn off the ports
>> self.usrp_sink_0.set_tx_lo_dist(False,"LO_OUT_0",0)
>> # repeat for all ports you enabled "LO_OUT_<N>"
>> The other settings i found were needed in the gr-uhd block included:
>> Setting the start time to 1
>> Setting the Master Clock rate to 200MHz
>> CH0:
>>   LO Source = external
>>   LO Export = True
>> CH1:
>>   LO Source = external
>>   LO Export = False
>> I'd like to thank the community of users for doing all of this work, 
>> especially Marcus Leech, Rob Kossler and Daniel Estevez
>