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Re: [Discuss-gnuradio] USRP2 PPS and REF

From: Douglas Geiger
Subject: Re: [Discuss-gnuradio] USRP2 PPS and REF
Date: Tue, 10 Feb 2009 15:14:03 -0600
User-agent: Thunderbird (Windows/20081209)

Eric Blossom wrote:

>> Since I've now tried this a few times
>> doing things like: removing the antenna from one (and not the other),
>> moving them far apart, etc. - I'm fairly certain this is a software
>> problem, and not the correct results.
> OK.  Just to be sure, are you explicitly specifying different mac
> addresses in the calls to usrp2::make?

Yes - I have two command line arguments, and when I print out
u2a->mac_addr().c_str() and u2b->mac_addr().c_str() I get the expected

>>  I can post my code if that would be helpful - I'm hoping I'm just
>> making some silly mistake with my calls to rx_samples, and the copy
>> handler or something similar. 
> Please post a link to your code.


>> E.g., should I be using different channel numbers?
> Nope, channel number zero is the only one you need.
>> I just updated the firmware on my USRP2's to r10377, and the fpga
>> bitstream to r10183.
> Eric

Somewhat more disturbing. I've turned off the 1Hz/1PPS, and I'm not
getting errors from sync_to_pps() (i.e. it still thinks they are
synchronized - even after power cycling). When I added the code to the
copy handler to print out the timestamp, etc. from the frame/metadata, I
still get identical timestamps being sent: i.e. when I run:
./rx_mimo -m 30:80 -n 30:81 -f 2.412G -d 128 -g 30 -N 500 -o test1.dat
-O test2.dat -v -M LOCK_TO_SMA

I get:
USRP2 (A) MAC address: 00:50:c2:85:30:80

Daughterboard configuration:

USRP2 (B) MAC address: 00:50:c2:85:30:81

Daughterboard configuration:

USRP2 (A) using decimation rate of 128
USRP2 (B) using decimation rate of 128
Started streaming
Receiving 500 samples

test1.dat: Timestamp: 1423196227(0,9.15527e-05) 0
test2.dat: Timestamp: 1423196227(0,9.15527e-05) 0
test1.dat: Timestamp: 1423243734(0.000274658,9.15527e-05) 0
Stest2.dat: Timestamp: 1423243734(0.000274658,9.15527e-05) 0
Copy handler called 2 times.
Copy handler called with 2968 bytes.

Elapsed time was 0.001 seconds.
Packet rate was 3040 pkts/sec.
Approximate throughput was  4.51 MB/sec.
Total instances of overruns was 1. (A)
Total missing frames was 254. (A)

This is with no 1PPS, no 10Mhz reference signal, and the antenna on
30:80 was removed (installed on 30:81). I'm going to pull up wireshark
to compare the frames I'm getting from each USRP2.

Doug Geiger
Research Assistant
Communications and Signal Processing Lab
Oklahoma State University

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