Combine PDU message data with stream data

My objective: In reference to the https://wiki.gnuradio.org/index.php/Packet_Communications#Using_BPSK_with_Hardware_Simulation_.28version_3.9.29 tutorial: it sends packets but has dead time in-between, which may cause the BPSK receiver to lose sync. I would like to fill the time (and stream) with an idle code so there is always a signal for the receiver. My latest attempt to use a Python Source block didn't work out - probably a timing problem or a lack of understanding of the scheduler.

This Embedded Python block receives a stream input of idle bytes and a PDU message input. It outputs the PDU message when received, otherwise it outputs the idle bytes. However, the PDU data never appears downstream.

Note: this flowgraph uses AFSK instead of BPSK, but the objective is the same.

See https://pastebin.com/GJgnzjCP   Embedded Python block

https://pastebin.com/C6XVsCZx       AFSK flowgraph

Any help will be appreciated.

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Barry Duggan KV4FV

https://github.com/duggabe