[Discuss-gnuradio] USRP control thread in GR block - how do I pass a USRP sptr?

[Nowlan, Sean]

I have a USRP with a GPSDO. I am working on a block that will poll a USRP for PPS changes in an attempt to adjust for clock offset between host and USRP. Assume I have explicitly set the USRP time-of-day correctly to UTC using PPS and a set_time_next_pps_call, and GPS is locked.

 

I would like to pass a USRP sink (or source) shared pointer to this block. It will have its own internal thread that will loop waiting for PPS edge transitions, polling with get_time_now, and then measuring offset between PC/system clock and USRP clock.

 

Following guidance from a mailing list thread [1], I attempted to pass a usrp_sink shared pointer as a basic_block_sptr and then dynamic_cast it in the block xtor. Here’s the error I get:

 

clock_manager_impl.cc: In constructor ‘gr::mymodule::clock_manager_impl::clock_manager_impl(gr::basic_block_sptr, double, const string&)’:

clock_manager_impl.cc:50:59: error: cannot dynamic_cast ‘usrp’ (of type ‘gr::basic_block_sptr {aka class boost::shared_ptr<gr::basic_block>}’) to type ‘gr::uhd::usrp_sink::sptr {aka class boost::shared_ptr<gr::uhd::usrp_sink>}’ (target is not pointer or reference)

         d_usrp(dynamic_cast<gr::uhd::usrp_sink::sptr>(usrp)),

 

Any advice on the best way to do this? Is my approach sane?

 

Thanks,

Sean