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

[Douglas Geiger]

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Matt Ettus wrote:
> Sync_to_pps is all about timestamps and the pps input, so it is not
> related to whether or not the clock is locked.

Right, got it.

> 
> Just to clarify the clocking architecture on the USRP2, there are
> basically 3 modes:
> 
>  - Free running
>  - Locked to the external SMA reference input
>  - Locked to the clock which comes over the MIMO cable from another USRP2
> 
> You need to make sure you are in the 2nd one, aka "we lock to SMA".  It
> sounds like whatever code you are running is setting the mode to "we
> lock to MIMO connector" mode.
> 
> Matt

You're correct - it looks like as soon as I call config_mimo, it looses
the lock to SMA. I'm a bit confused as to why that is - I'm calling it
with MC_WE_LOCK_TO_SMA which is defined in usrp2_mimo_config.h - it
basically comes out as 0x0001 (i.e. _MC_WE_LOCK | 0, where _MC_WE_LOCK
is 0x0001).

- --
Doug Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
address@hidden
address@hidden
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