Re: [Discuss-gnuradio] UHD disable receive

[Josh Blum]

> When sending from A to B, I receive A's message on B. The problem is I
> also receive A's message on A. Same happens when going from B to A. Is
> this normal? I know the RFX2400 is full duplex, but this was not what
> I was expecting. Is there any way to disable the receive path while
> transmitting?
> 

I might suggest:
1) shut off the demodulation in software when transmitting.
2) transmit and receive on different frequencies.
3) reject the received packet at the mac layer

In any case, you can shutoff the rx mixer in full duplex mode with this
little change:
> diff --git a/host/lib/usrp/dboard/db_rfx.cpp b/host/lib/usrp/dboard/db_rfx.cpp
> index 725b5cc..e12091b 100644
> --- a/host/lib/usrp/dboard/db_rfx.cpp
> +++ b/host/lib/usrp/dboard/db_rfx.cpp
> @@ -198,7 +198,7 @@ rfx_xcvr::rfx_xcvr(
>      //setup the rx atr (this does not change with antenna)
>      this->get_iface()->set_atr_reg(dboard_iface::UNIT_RX, 
> dboard_iface::ATR_REG_IDLE,        _power_up | ANT_XX | MIXER_DIS);
>      this->get_iface()->set_atr_reg(dboard_iface::UNIT_RX, 
> dboard_iface::ATR_REG_TX_ONLY,     _power_up | ANT_XX | MIXER_DIS);
> -    this->get_iface()->set_atr_reg(dboard_iface::UNIT_RX, 
> dboard_iface::ATR_REG_FULL_DUPLEX, _power_up | ANT_RX2| MIXER_ENB);
> +    this->get_iface()->set_atr_reg(dboard_iface::UNIT_RX, 
> dboard_iface::ATR_REG_FULL_DUPLEX, _power_up | ANT_RX2| MIXER_DIS);
>  
>      //set some default values
>      set_rx_lo_freq((_freq_range.start() + _freq_range.stop())/2.0);


> After digging around I found a set_auto_tr function that sounded like
> it would fix this problem, but for some reason it looks like that is
> not implemented for gr-uhd. Any suggestions on how to fix this?
> 

The auto tr is always enabled on uhd. What it does is set antenna
switches and mixers based on the state of the device. I don't think its
what you are looking for. This might be relevant:
http://www.ettus.com/uhd_docs/manual/html/dboards.html#rfx-series

-Josh