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

[Martin Braun]

Marcus is right, but your approach should technically work as well. I rarely get C++ polymorphisms and pointers right at first go, but using dynamic_pointer_cast should work and be safe - ish.

M

On 29 Jan 2016 10:28, "Marcus Müller" <address@hidden> wrote:

Sorry, I just got a friendly reminder that this is a bad idea in many ways; the recommended way of getting a handle to your USRP block is passing the block alias around and looking it up in the block registry; that's why we have it anyway.
Make sure the result of the lookup is valid!

Best regards,
Marcus

Am 29. Januar 2016 09:13:42 MEZ, schrieb "Marcus Müller" <address@hidden>:

Hi Sean,

it's been a while since I did that, but I think that "smart_ptr<A> cannot be casted to smart_ptr<B>" can be remedied using Boost's pointer_cast[1].

Hope that gives you a start.

Best regards,
Marcus

[1] http://www.boost.org/doc/libs/1_60_0/libs/smart_ptr/pointer_cast.html

On 01/28/2016 08:34 PM, Nowlan, Sean wrote:

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

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