Re: [Discuss-gnuradio] USRP's not Communicating

Ah sorry I wasn't specific.  This was from years ago, the numbers I used were just meant to be an example, not accurate.

On Tue, Aug 25, 2015 at 10:25 PM, Marcus D. Leech <mleech@ripnet.com> wrote:

On 08/25/2015 10:17 PM, devin kelly wrote:

You can have each USRP on the same computer or not, that shouldn't matter.

I've done this test with some USRP2's and I remember what we did was transmit a CW tone from one to another and measure a frequency offset (maybe 10s of kHz?).  Basically, transmit a tone at some known frequency (like 200 MHz) and measure the received frequency (maybe something like 200.02 MHz) and then add the 0.02 into you center frequency for this test. 

You can also just synchronize the USRPs with a 10MHz reference and 1PPS.

Devin

The USRP2 uses a 2.5PPM master on-board clock, so at 200Mhz tuned frequency, the max it can be off is about 500Hz.  For narrowband transmission,
  that may be too much, but I'd be very surprised to see 20kHz offset with a 200MHz carrier.

On Tue, Aug 25, 2015 at 5:14 PM, John Garrick <lists@ruby-forum.com> wrote:

Hello,

I want to transmit the data between two USRP's and make them communicate
with each other. But I guess the packets are not being received
properly.
I am connected the two USRP's to the same laptop and trying it. Is that
applicable? I mean, will it work if I do that? Or should I connect to
two computers and perform that? I have been receiving this error.

linux; GNU C++ version 4.8.4; Boost_105500;
UHD_003.009.git-144-g407e3086

Using Volk machine: avx_64_mmx
-- Opening a USRP1 device...
-- Using FPGA clock rate of 64.000000MHz...

No gain specified.
Setting gain to 56.250000 (from [0.000000, 112.500000])

UHD Warning:
    The hardware does not support the requested RX sample rate:
    Target sample rate: 0.050000 MSps
    Actual sample rate: 0.250000 MSps

Symbol Rate:         25000.000000
Requested sps:       2.000000
Given sample rate:   250000.000000
Actual sps for rate: 10.000000

Requested sample rate: 50000.000000
Actual sample rate: 250000.000000
ok = False  pktno = 53034  n_rcvd =    1  n_right =    0
ok = False  pktno =   24  n_rcvd =    2  n_right =    0
ok = False  pktno =   35  n_rcvd =    3  n_right =    0
ok = False  pktno =   44  n_rcvd =    4  n_right =    0
ok = False  pktno =   46  n_rcvd =    5  n_right =    0
ok = False  pktno =   46  n_rcvd =    6  n_right =    0
ok = False  pktno = 3872  n_rcvd =    7  n_right =    0
ok = False  pktno = 12304  n_rcvd =    8  n_right =    0
ok = False  pktno =   49  n_rcvd =    9  n_right =    0
ok = False  pktno =   50  n_rcvd =   10  n_right =    0
ok = False  pktno =   54  n_rcvd =   11  n_right =    0
ok = False  pktno =  200  n_rcvd =   12  n_right =    0
ok = False  pktno =   63  n_rcvd =   13  n_right =    0

Please suggest. Thank you

Regards,
Ravi

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