Hello, I'm currently working on a multithreaded application which needs to set the gain value of a USRP sink at runtime. The only thing I've found that works so far is:
stop() -> wait() -> lock() -> set_gain() -> unlock() -> start() I tried using just lock/unlock, but this causes the SDR to freeze completely. As it is, the current setup causes stability issues and crashes after only a few minutes at best. I've heard about sending commands to the USRP Sink, though I couldn't find any documentation on the subject and the one page I found has been removed (and was never archived). Here's the message I keep receiving from the flowgraph: gr::log :FATAL: tagged_stream_mux0 - Missing a required length tag on port 1 at item #100 thread[thread-per-block[10]: <block tagged_stream_mux(14)>]: Missing length tag. It seems to happen at random with any tagged block in the flowgraph (the point of failure typically changes every time we run it). While we could theoretically just catch the error and restart the flowgraph, I would rather find a more permanent solution. We're using two Ettus B200 SDRs for our current tests. If anyone has any information on proper dataflow control for blocks or the USRP sink message passing API, I'd really appreciate it. Thanks, Guy Marino
