[Discuss-gnuradio] _post to message port with python handler

[Jared Dulmage]

This is a follow-up to a prior question I asked under the title 'message 
passing: _post or strobe' that didn't get much attention.

I was trying to use basic_block._post from python to send messages to a python 
block in my flowgraph.  As a sanity check I also tried using a message_strobe 
block, connecting the message_strobe output message port to my python block's 
input message port.  The message_strobe block uses 
basic_block::message_port_pub which indirectly calls basic_block::_post.

Running my fg in gdb I was able to verify that basic_block::_post was being 
called in both instances and that the which_port and msg arguments were 
correct.  However, I could not determine why my message handler was called only 
when triggered with message_port_pub (via the message_strobe block) and not 
when I used _post directly (from python).

The workaround was to have my python block also register an output port, 
connect it to its input message port, and use blk.message_port_pub from within 
my python script.  It seems some state must be set using msg_connect and/or 
message_port_pub that is required for _post to work.  I was unable to determine 
that but at least I have found some way to get it to work.

I appreciate anyone's comments or suggestions.

Jared.
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Jared Dulmage
Engineering Specialist
Digital Comm. and Implementation Dept.
Aerospace Corporation
310-336-3140