Re: [Discuss-gnuradio] USRP2 and external clock (from GPS receiver)

[Matt Ettus]

Changkyu Seol wrote:
> Hi!
>
> I am planning to implement multiple synchronized transmitters using
> USRP2 and GPS receiver. Before that I checked whether the USRP2 is
> locked to external clock through following experiment.


The easiest way to check for lock is to put the following line in your 
firmware:

        clocks_enable_test_clk(true,10);

This will output a test clock on the middle 2 pins of the 4 pin 
connector right near the VCXO on the motherboard.  Look at one of those 
2 pins on an oscilloscope at the same time as the 10 MHz reference.  You 
should see the two clocks don't drift relative to each other.

Matt