Re: [Discuss-gnuradio] usrp2: timestamp absolute ?

[Eric Blossom]

On Mon, May 11, 2009 at 08:12:08PM +0200, Michael Sprauer wrote:
> Hello list,
> 
> my question is about the time stamp in rx_metadata->timestamp. I've got the 
> rx_streaming_samples running and now I wondering what the time value is about.
> In the code I've found this:
> uint32_t      timestamp;      // time of rx or tx (100 MHz)
> 
> Can you tell me what the timestamp exactly refers to. Is it just a counter? 

It's a counter clocked by the 100 MHz s.ample clock.

> When/How is it started/reseted?

If you don't do anything, it's initialized to 0 at power up.

You can arrange so that it's reset to zero on the next pulse on the
pulse-per-second input using usrp2::sync_to_pps.


> Or to be more precisely: How do I calculate an absolute time like the 
> extended 
> unix time stamp with uSec and nSec?

At this point you don't.  We'll be moving to a 64-bit format when we
convert the USRP2 to use the VRT on-the-wire format


> Thanks for reading :)

You're welcome :-)

Eric