Re: [Discuss-gnuradio] Message API questions

[Aditya Dhananjay]

On Wed, Feb 26, 2014 at 8:45 AM, Nowlan, Sean <address@hidden> wrote:

I have a few questions regarding messages in GR.

 

1)      Is it possible to mix-and-match the old style message sink/source blocks with the new style message passing API? Any guidance on how to make the connections? I didn’t have much luck with msg_connect. I don’t think the message sink/source blocks have an associated port name to make this possible. Perhaps that’s something worth adding internally?

I'm not sure I completely understand your question.

Have you looked at the OFDM Tx/Rx examples in PATH/gr-digital/examples/ofdm? The flowgraph is a combination of standard connections within blocks, along with a message passing connection (look at the header/payload demux block).

 

2)      I see 2 implementations of msg_queue, one in gr namespace and one in gr::messages namespace. What are the differences between these?

 

3)      How does one achieve flow control with the new style message passing API? I have a use case in which I’m generating packets in one flowgraph and pushing them through a pdu_to_tagged_stream (P2TS) block to be modulated in another flowgraph. I believe I’m overwhelming the P2TS block’s queue because I get warnings about dropped messages. One hack I made was to insert a throttle block into the packet generating flowgraph. This helped a bit, but I have to guess the magic throttle rate at which I don’t fill up the queue. Is there a way to have P2TS block when its queue is full and therefore generate backpressure on the upstream flowgraph?

Are you using actual hardware or is this a software only simulation?

 

 

 

Thanks!

Sean

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