Re: [Discuss-gnuradio] Using PPS to trigger received data storage in Python

[Yan Nie]

Thank you so much for your suggestions, Josh. 

Your suggestion on solving the problem I met is absolutely creative. Thank you 
so much! 

I have more further detailed questions related:
get_time_last_pps gives a timespec representing the last pps, while how can I  
obtain the stream tags from the my down stream block? Can I get the stream tags 
in Python, as from a post on my gnuradio discuss list, stream tags 
functionality had not pulled into mainline gr-uhd yet until this Sep.?

Then combine these two timespec together to control which samples would be 
stored. I am using the file_sink block to create a data file and store the data 
in. If using these timespec information to store the samples, I think it needs 
to correspond the certain stream tags when pps pulse occurs (timespec given by 
get_time_last_pps) to the exact sample stored in the data file created by 
file_sink. Therefore, I am wondering how this stream tags correspond to data 
samples in the data file, as the data file only stores data samples from my 
understanding?

> Continually read get_time_last_pps(). Every time this function returns a
> different value, you know the exact time (relative to USRP) that a pulse
> event occurred.
> 
> So you know:
> 
> 1) the exact time for every sample thanks to stream tags
> 2) the exact time of every pulse thanks to get_time_last_pps
> 
> Now you just have make some code that combines both pieces of
> information to store the samples.