[Discuss-gnuradio] ptime get_time(void) precision down to millisec microsec nanosec ?

[Bastien Auneau]

Hi Everyone

First, I would like to introduce myself (ourselves) :
VeriSat, Oslo based company (Norway). We are working on a project, using
USRP (N210) platform, which aim is to build a DVB-RCS Terminal
Shortly RCS is for satellite communication, and is Multi Frequencies
TDMA. (http://verisat.no)

So synchronization is an important issue for us.
Now I have a question regarding the use of a USRP N210 with GPSDO kit,
and the use of the UHD function ptime get_time(void) in
/host/lib/usrp/gps_ctrl.cpp @ line 133

According to the implementation of get_time(void), it returns the date
time with precision down to second. It looks like it queries the USRP
waiting for a reply starting with "$GPRMC". then is parses the reply to
extract year, month, day, hours, min and sec.

Is it possible to extract from the reply the milli ? micro ? and nano
seconds ? For example using toked[2-8] or toked[10-11] (because
UHD_ASSERT_THROW(toked.size() == 12);)

If not, is there any way to include more precision in get_time() by
changing code not only in gps_ctrl.cpp, but also in the firmware ?

According to
http://lists.gnu.org/archive/html/discuss-gnuradio/2011-02/msg00162.html
USRP should get 50 ns precision, so I assume it's possible in some way ?

Best Regards
Bastien