[Discuss-gnuradio] delay of Synchronization by using PPS

[闷 郁]

hi guys,
Im using a USRP-N and a USRP2 to send a Square Signal to another USRP2 for proving Synchronization by using PPS.

after execute a get following message:


linux; GNU C++ version 4.6.3; Boost_104800; UHD_003.007.000-1-stable

Using Volk machine: sse4_1_32
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
--     1) catch time transition at pps edge
--     2) set times next pps (synchronously)
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
--     1) catch time transition at pps edge
--     2) set times next pps (synchronously)
-- Opening a USRP2/N-Series device...
-- Current recv frame size: 1472 bytes
-- Current send frame size: 1472 bytes
--     1) catch time transition at pps edge
--     2) set times next pps (synchronously)


It seems to work well,but when i look into the scope sink i found a pretty randomed delay between 2 Transmitters.
it looks like this: --˜˜˜--___--˜˜˜--___--˜˜˜--___--˜˜˜--___
after restart it would look like this:-˜˜˜˜-____-˜˜˜˜-____-˜˜˜˜-____-˜˜˜˜-____

I tried set a delay-block to compensate,but i realize coz of random i cant find a constant delay.
did I do something wrong or there is a certain way to "tell" the 2 Transmitters send Signal in the same time?


Yao