[Discuss-gnuradio] Using UHD, trying to tx and rx samples simultaneously

[Isaac Gerg]

I am using the USRP1 with a Basic RX and Basic TX.  I want to send a message out the Basic TX and receive it with my Basic Rx.  I am using the Complex Float32 datatype.

Using Device: Single USRP:
  Device: usrp1 device
  Mboard: usrp1 mboard - 48cc208a
  RX DSP: usrp1 ddc 2X + hb
  RX Channel: 0
    RX Dboard: usrp1 dboard (rx unit) - A
    RX Subdev: Basic RX (0x0001) - AB
  TX DSP: usrp1 duc 2X 
  TX Channel: 0
    TX Dboard: usrp1 dboard (tx unit) - A
    TX Subdev: Basic TX (0x0000) - AB

Setting RX Rate: 250000.000000 sps...
Actual RX Rate: 250000.000000 sps...

Setting RX Freq: 0.100000 Mhz...
Actual RX Freq: 0.100000 Mhz...

Setting RX Gain: 0.000000 dB...
Actual RX Gain: 0.000000 dB...

Setting TX Rate: 0.250000 Msps...
Actual TX Rate: 0.250000 Msps...

Setting TX Freq: 0.100000 Mhz...
Actual TX Freq: 0.100000 Mhz...

Setting TX Gain: 0.000000 dB...
Actual TX Gain: 0.000000 dB...

I have used the code from http://ettus-apps.sourcerepo.com/redmine/ettus/projects/uhd/repository/revisions/master/entry/host/examples/ to set up software which has three threads.  The first thread spawns two threads a rx and tx.  The rx keeps receiving until it get the message from the tx.  The tx sends a 94 sample message every 10 seconds.  

The rx thread looks at the data and prints out a message when the data.real()>0.01.  (The data is normally (0,0).

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.

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

Isaac