Hi Rich, sounds like a job for gr-eventstream[1] to only put in info when some event occured (i.e. when a message was sent to the eventstream block), and maybe gr-msgtools to convert the change in variable value from a "QT GUI Pushbutton" to a message, and a self-written (might be simple enough to do in Python) block that has a message input and a message output and, upon change, sends a event-stream-event-compatible message to the event stream source, containing the contents of the file. Then you'd write a mux and be done.
To be completely honest, though it's a bit like re-inventing gr-eventstream, I'd probably just use the aforementioned pushbutton, convert its pushbutton variable change to a message using gr-msgtools' Variable To Message block to convert that to a variable, and write a quick C++ or python block that has a "passthrough" stream input, a "interject" message input, and a stream output. Whenever there's a "pressed" message, it would disrupt its normal activity of passing through the input, and change into a state of inserting samples from a file, till the complete file is read completely. Sounds like not-so-much code. Note that message handling happens asynchronous, ie. only *in between* calls to work. So, always consider that handling a message of this sorts has a worst-case latency of f_sample * size_of_output buffer + Python/Qt overhead. Luckily, you can restrict the output buffer size, or you could even intentionally never produce too many samples at once. Best regards, Marcus [1] https://oshearesearch.com/index.php/2015/03/15/burst-transmission-in-gnu-radio-sample-streams-with-eventstream/ On 25.07.2016 20:28, Richard Bell wrote: > Hello, > > I need to let the user select which input stream to transmit by > pushing a button on the GUI. By default, the transmitter transmits > random data until the user clicks the button, at which point a file is > transmitted. > > It is important that the entire file be transmitted, from the > beginning. This means that the file data stream can't be dropped to > the floor until the user clicks the button, it must apply back > pressure from the selector block to the file source block until the > user presses the button. > > The selector block uses a null sink for each stream that isn't > connected to the output, so I loose the ability to send the file from > the beginning. In addition, the selector is causing the flowgraph to > close with return code -11 and no other message. > > Does someone have an idea of how I could do this using GRC? > > Thank you, > Rich > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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