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

[Douglas Geiger]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

Douglas Geiger wrote:
> 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).
> 

 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 Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University
http://cspl.okstate.edu
address@hidden
address@hidden
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFJnwx7gfOzzR5bXIgRAkgeAJ9c+Zt+R3Pp/iH2JAzI5ulAFPXEvQCfdfWM
CTWdJOXlQT1u8+R1zp4/kv8=
=ATyU
-----END PGP SIGNATURE-----

Index: usrp2_impl.cc
===================================================================
--- usrp2_impl.cc       (revision 10441)
+++ usrp2_impl.cc       (working copy)
@@ -995,6 +998,7 @@
     cmd.op.opcode = OP_CONFIG_MIMO;
     cmd.op.len = sizeof(cmd.op);
     cmd.op.rid = d_next_rid++;
+    cmd.op.flags = flags;
     cmd.eop.opcode = OP_EOP;
     cmd.eop.len = sizeof(cmd.eop);