USRP2 and external clock (from GPS receiver)

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Matt E. wrote:

external source - which in this case is a function generator with a
10MHz sine with 2V P-P.

Is it possible some of the hardware on my USRP2’s isn’t working?

Unlikely, since it was tested before shipping.

I will send you code to run in a separate email.

Matt

Ok - now that I’ve discovered I had some bad cabling - specifically a
bad T-splitter: the side going to my O-scope worked, the side going to
my USRP2’s did not - which I suppose can be chalked up to user error.
I am now able to synchronize the clocks - both with the firmware/fpga
code you sent, and the version I had built locally.
However - once I start running my code on the host PC, the clock loses
sync. I have to power down, and re-power-up the USRP2 for the clock to
lock onto my external source again. This is with the firmware/fpga from
svn r10441, and my host code. I’ve tried calling ->config_mimo and

  • ->sync_to_pps() as soon as I create my USRP2 objects, but that didn’t
    seem to help.
    Doug

Doug G.
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
[email protected]
[email protected]
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Douglas G. wrote:

  • Locked to the external SMA reference input
    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).

It looks like usrp2_impl.cc never passes on the argument when you call
config_mimo - I’ve attached a quick patch that I believe does the job
correctly.
When I run my host code now the clocks on my USRP2’s remain
synchronized to my external source.
Doug


Doug G.
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
[email protected]
[email protected]
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On Fri, Feb 20, 2009 at 02:03:08PM -0600, Douglas G. wrote:

It looks like usrp2_impl.cc never passes on the argument when you call
config_mimo - I’ve attached a quick patch that I believe does the job
correctly.
When I run my host code now the clocks on my USRP2’s remain
synchronized to my external source.
Doug

Fixed in 10471. Thanks!

Sorry for the trouble it caused you.

Eric