Configuring the slave for MIMO cable

GNU Radio
1

Hello,
I’m trying to configure the slave device so I can use a MIMO cable with
2 of
my USRP N210’s. I see the application notes for the N210 where it says
you
need to configure the slave with:

uhd::clock_config_t clock_config;
clock_config.ref_source = uhd::clock_config_t::REF_MIMO;
clock_config.pps_source = uhd::clock_config_t::PPS_MIMO;
usrp->set_clock_config(clock_config, slave_index);

My question is, where do I make these changes exactly? I found a clock
config file that has syntax similar to this but nothing that matches it
and
I don’t want to mess anything up. Any help is greatly appreciated,
thanks!
Wes

–
Wes R.
Graduate Research Assistant
219 Engineering Research BuildingWVU CSEE

[email protected]
[email protected]

2

On 08/10/2011 09:57 AM, Wes R. wrote:

My question is, where do I make these changes exactly? I found a clock
config file that has syntax similar to this but nothing that matches it and
I don’t want to mess anything up. Any help is greatly appreciated, thanks!

I’m not sure what you are asking. If you make a quick flow graph in grc
and set the reference source to “mimo cable”, generate the code, you can
inspect the code for how to do it in python.

-josh

3

I’m sorry I wasn’t clear. I thought before I could do anything MIMO in
the
GRC I had to change some configuration files because of that block I
quoted
from the N210 Application notes on the Ettus site. Are you saying I
don’t
need to change anything, I can just set the reference to MIMO and move
on?
Thanks,
Wes

Josh B.-3 wrote:

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4

I see what you meant Josh, thanks for your help. One more quick
question, as
simple as it seems I still have to make sure. In the flowgraph in GRC I
will need 2 UHD sources right? One with the default ref source and one
with
the MIMO cable as its source. Assuming that’s correct, is there a way I
can
add the 2 streams in order to decode the incoming data, (in my case
streaming video)?

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5

That makes perfect sense now, thanks. Now that there are 2 channels I
have 2
outputs which I can’t directly feed into my demodulator/decoder. Is
there a
way in GRC to combine the 2 streams in order to only have 1
demod/decoder
with the hopes of observing the array gain from the 2nd USRP at my
output?

Josh B.-3 wrote:

-josh

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6

On 08/15/2011 12:07 PM, wes.rumble wrote:

I see what you meant Josh, thanks for your help. One more quick question, as
simple as it seems I still have to make sure. In the flowgraph in GRC I
will need 2 UHD sources right? One with the default ref source and one with

Use exactly one source block w/ 2 channels. That way, uhd performs the
time-alignment of the streams.

Example of the device addressing for multiple mboards:
http://www.ettus.com/uhd_docs/manual/html/usrp2.html#multiple-device-configuration

-josh