Hi Marcus - thanks for the link to the documentation. Messages don't have the required functionality, so I have tried to insert tx_sob and tx_eob tags. This unfortunately has not changed anything. This is what the tag debug shows, are these formatted correctly for UHD USRP sink?
---------------------------------------------------------------------- Tag Debug: Input Stream: 00 Offset: 139250 Source: burst_tagger4 Key: tx_sob Value: #t ---------------------------------------------------------------------- ---------------------------------------------------------------------- Tag Debug: Input Stream: 00 Offset: 196587 Source: burst_tagger4 Key: tx_eob Value: #t ---------------------------------------------------------------------- I have to stop streaming samples to the USRP Sink to get it to stop transmitting and switch TX/RX over to RX - the tags aren't enough. However the next time back to Tx, the problem with transmitter underruns and weird oscillating T/R behavior resumes. Still looking for advice as to how to T/R switch the unit without the TX going nuts? -- Tom, N5EG On 07/04/2019 11:14 PM, Tom McDermott via USRP-users wrote: >* I am trying to use a B205mini in half-duplex mode through the TX/RX *>* connector *>* from a GRC flowgraph. Gnuradio 3.7.13.4. Very slow switching, *>* manually implemented. *>>* The flowgraph implements a simple half-duplex transceiver. In order to *>* switch *>* the TX/RX antenna switch, I am starting and stopping samples to the *>* USRP sink *>* using the Copy block. When the Copy block is enabled it passes *>* samples to the USRP sink, *>* and when disabled it does not copy samples to the USRP sink. *>>* If the Copy block is statically enabled, then the USRP transmits (RED *>* led 'On' for TX/RX) *>* continuously without any underruns. *>>* If the Copy is statically disabled, then USRP goes into receive mode *>* (GREEN led 'On' for TX/RX) *>* and stays in that mode. *>>* So far so good. *>>* However if I toggle the enable/disable on the copy block to disable *>* the TX/RX switches as it should *>* from red to green, but after I re-enable the Copy block and leave it *>* enabled, the TX/RX LED goes red *>* for awhile, then rapidly flashes red/green/red etc. while printing *>* UUUUUUU on the GRC console, then *>* goes RED for about 5 seconds without underruns, then flashes RED/GREEN *>* rapidly for 5 or 10 seconds *>* and underruns, back and forth ad infinitum. *>>* So Copy appears not to be a good way to implement T/R switching. *>>* There is a message port on the USRP sink block. Can this be used to *>* implement T/R switching? *>* Is there some place that the messages that this port accepts defined? *>* I cannot seem to find *>* the syntax for the message definitions in the USRP documentation, so I *>* must be looking in the wrong place. *>>* -- Tom, N5EG *>>There's some documentation here: https://www.gnuradio.org/doc/doxygen/classgr_1_1uhd_1_1usrp__sink.html
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