Re: [Discuss-gnuradio] Using external clock references in GRC environment

[Johnathan Corgan]

On Wed, Jun 6, 2012 at 9:22 AM, Nazmul Islam <address@hidden> wrote:

 

I am sorry for not clarifying on the "strange output" last time. In my experiment, I am transmitting an LFSR PN sequence. Thereafter, I correlate the transmitted PN sequence with the received baseband complex I & Q. If there were no timing error between the two USRP's, then I would get high correlation after every chip sequence period.

It looked like on your last email that your GRC flowgraph has the USRP source sample rate set to 32Ksps.  This is not a sample rate producible by the USRP; in fact, in the bottom portion of the GRC window, you should see an error message telling you what it actually set the sample rate to.  If this is different from the transmitter, then you will get what you are seeing (or worse.)

You should look at what the allowable sample rates are for your transmitter and receiver USRPs, then pick a common one and set that as the variable 'samp_rate' in your GRC flowgraph on both sides.  For purposes of your experiment, I'd choose the lowest sample rate possible; later, you might try increasing this as CPU performance allows.

Johnathan