PSK31 dynamic TX flow

I’m experimenting with PSK31 transmission. I can transmit bits streamed
from a file, but to take it to the next level, I need to dynamically
switch between keyboard keystroke generated data and a repetitive 1010
without stopping the flow.

Is there a way in GRC (or the main GR python script) to dynamically
select between a signal source and a file source, using the signal
source when the file source is empty? The file source would be a FIFO
that I would fill with an external python script that translates
keyboard strokes into a varicoded bit stream. When that FIFO is empty I
need to switch back to the alternating 1010. I’d rather not source the
1010 from the FIFO since that may lead to timing issues.

I’m trying to avoid, in the short term, writing a custom GR source
block, but that may be inevitable. I read there is a way to probe data
in the flow; is there a way to stuff bits into a stream?



You can use a socket-to-pdu block, and write an external python
to send repeating data or pass along key strokes through the socket.
Use a
Pdu-to-tagged-stream to convert to a stream of bytes that in turn
stimulated the modulator blocks. That’ll make integration and
customization a little easier than starting with a new, custom block.