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Re: [Discuss-gnuradio] any alternative API for set_auto_tr when using xc

From: Matt Ettus
Subject: Re: [Discuss-gnuradio] any alternative API for set_auto_tr when using xcvr2450+usrp2
Date: Mon, 02 Mar 2009 12:35:50 -0800
User-agent: Thunderbird (X11/20090105)

Johnathan Corgan wrote:
On Thu, Feb 26, 2009 at 9:14 PM, Xiaolong Li <address@hidden> wrote:

Can I still call set_auto_tr to enable auto switch Rx and Tx with
xcvr2450+usrp2? It seems like the set_auto_tr is no longer available. Is
there any alternative API for same function? Without calling set_auto_tr,
USRP2+xcvr2450 can receive normally, however, no luck for transmission.
Could anybody explain why this happens? Thanks.

The standard firmware build has transmit on one antenna port and receive on the other. So you can either change the software to put them both on the same antenna port, or you can use 2 separate antennas.

The USRP2 is *always* in auto T/R mode; that is, it does not support
full duplex without a modification to the FPGA and firmware code.

I'd like to clarify that statement a bit. Full duplex operation requires modified firmware and host code. The as-released FPGA image itself has no limitations that we know of when it comes to full duplex operation.

The Auto-T/R issue is separate. If you want to operate full duplex, the Auto-T/R settings need to be modified so to send RX to one port and TX to the other port, regardless of whether you are transmitting or not.

Also, please note that the RFX-series boards can do full duplex, but the XCVR2450 cannot transmit and receive simultaneously. The act of transmitting turns off the receiver, so no amount of software will ever change that. It is perfectly fine for TDD, TDMA, CDMA, and FDMA type systems, but it will not do FDD.


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