External Manual control of T/R Switch

The RFX (FLEX) series of transceiver daughtercards include an onboard
T/R switch to allow a half-duplex setup using the Tx/Rx connector
and a single antenna.

In GnuRadio 3.3.0, under GRC, the choices for the “Transmit” parameter
on a USRP Sink Block seem to be limited to “Unconfigured”,
“Enabled”, or “Auto T/R”.

Since my application continuously produces transmit data, even while
idle, I want to be able to manually control the T/R switch from
an external entity, probably via a GRC variable that is set from
a message source or UDP source.

Is this even doable? GRC’s block parameter editor does not show
this parameter as underlined, meaning it cannot be changed dynamically.

Would it be possible to dynamically control the transmit_enable by
calling the appropriate method using a probe block?

Although this application is locked into using GR 3.3.0, I’ve also
looked at the GR 3.5.1 xml description for a GRC UHD_sink block, and
can’t even find where the transmit enable is.

Any help on this?

@(^.^)@ Ed