Forum: GNU Radio any alternative API for set_auto_tr when using xcvr2450+usrp2

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Xiaolong Li (Guest)
on 2009-02-27 07:15
(Received via mailing list)
Hello all,

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.

Best regards,
Xiaolong
Johnathan C. (Guest)
on 2009-03-02 22:20
(Received via mailing list)
On Thu, Feb 26, 2009 at 9:14 PM, Xiaolong Li 
<removed_email_address@domain.invalid>
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 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.

Thus, there is no auto TR configuration in the USRP2 host code.  Have
you verified that it is in fact not transmitting, not just that the
receiver doesn't see any packets?

Regarding the XCVR2450, support in the USRP2 has undergone a lot of
changes/bug fixes in the last few weeks.  Can you retest with at least
revision 10524 of both the FPGA and and firmware?  The binaries are
posted on the GNU Radio website.  These will require you to have
installed at least that revision of the GNU Radio trunk.

Johnathan
Matt E. (Guest)
on 2009-03-02 22:39
(Received via mailing list)
Johnathan C. wrote:
> On Thu, Feb 26, 2009 at 9:14 PM, Xiaolong Li <removed_email_address@domain.invalid> 
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.

Matt
Johnathan C. (Guest)
on 2009-03-02 23:16
(Received via mailing list)
On Mon, Mar 2, 2009 at 12:35 PM, Matt E. <removed_email_address@domain.invalid> 
wrote:

>> 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.

Sorry I was unclear--thanks for the clarification.

Johnathan
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