Re: [Discuss-gnuradio] Synchronized packet transmission

[Josh Blum]

On 01/03/2011 12:15 PM, Sangho Oh wrote:
> If I synchronize two USRPs using pps clock
> 
> uhd::time_spec_t time_spec = uhd::time_spec_t(0.0);
> sdev->set_time_next_pps(time_spec);
>         boost::this_thread::sleep(boost::posix_time::seconds(1));
> 

You may want to print out sdev->get_time_now().get_real_secs() to see
that it really got the PPS edge.

> and give the metadata for the frame as following
> 
>         md.time_spec = uhd::time_spec_t(seconds_in_future);
> 
> When is the packet is being transmitted?
> I believe md.time_spec specify the delay of transmission, which is not an
> absolute time of the transmission.
> 

md.time_spec is an absolute time

there is a working example in uhd/host/examples/tx_timed_samples.cpp

-Josh