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Re: [Discuss-gnuradio] Using UHD, trying to tx and rx samples simultaneo

From: Josh Blum
Subject: Re: [Discuss-gnuradio] Using UHD, trying to tx and rx samples simultaneously
Date: Wed, 26 Jan 2011 16:00:28 -0800
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv: Gecko/20101208 Lightning/1.0b2 Thunderbird/3.1.7

> When i start the program up.. the rx prints out a bunch of samps.  Then it
> stops.  10 seconds goes by. the tx thread wakes up and sends its first
> message, the rx gets nothing.  10 more seconds goes  by, the tx sends out
> another 94 sample message.  Now, TONS of samples come out.  In fact, the
> program print indefinitely.

Are you setting end of burst when you send the 94 samples? Unlike the
other usrps, USRP1 will not necessarily flush to the transport layer
unless it sees EOB.

Without the EOB, it only sends 512 byte multiples and stores the
remainder. Since 94*4 is less than 512 bytes, nothing is sent on the
first transmit, and the data is stored. But by the next run, the buffer
has 94*4*2 which is enough to send 512 bytes and store a remainder of
240 bytes.

> What is going on here?  It seems like the AGC is getting modified after the
> 2nd tx.   Is this true?

No such thing happens


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