Re: [Discuss-gnuradio] Problem with messages and msg_queue

[Eric Blossom]

On Wed, May 09, 2007 at 08:12:05PM +0200, Trond Danielsen wrote:
> Hi everyone,
> 
> I've got a problem with messages and message queues. The problem is
> simply that I just cannot figure out how to use them. I tried the
> simple program that is attached to this email (test.py), and the
> result is in test.log. If anybody has the time to take a quick look at
> the code and point me in the right direction, I would be very
> thankful!
> 
> Regards,
> 
> -- 
> Trond Danielsen


This looks correct, and in fact you are receiving a payload that's 800
bytes long (== 200 * sizeof(float)), so everything looks good.

In reality, you'd want to do something with the payload:

  payload = msg.to_string()  # return payload as an python string

  foo = struct.unpack(format, payload)

See gnuradio-core/src/python/gnuradio/blksimpl/pkt.py for a real-life example.

Eric




> #!/usr/bin/env python
> 
> from gnuradio import gr
> 
> class testing(gr.top_block):
>     def __init__(self):
>         gr.top_block.__init__(self, "testing")
> 
>         self.src = gr.vector_source_f( range(200), False )
> 
>         self.mq = gr.msg_queue()
>         self.sink = gr.message_sink(gr.sizeof_float, self.mq, False)
>         self.connect( self.src, self.sink )
> 
> def main():
>     top_block = testing()
>     runtime = gr.runtime(top_block)
> 
>     try:
>         runtime.start()
> 
>         print "queue"
>         print top_block.mq.count()
> 
>         msg = top_block.mq.delete_head()
>         print "msg"
>         print msg.type()
>         print msg.arg1()
>         print msg.arg2()
>         print msg.length()
> 
>         runtime.wait()
>     except KeyboardInterrupt:
>         pass
> 
> if __name__ == "__main__":
>     main()
> 
> # vim: ai ts=4 sts=4 et sw=4
> 

> connecting: vector_source_f(1):0 -> message_sink(2):0
> Setting runtime on 0x6923a0 to 0x6918c0
> start: entered
> flattening testing
> Flattening edge vector_source_f(1):0->message_sink(2):0
> Validating block: message_sink(2)
> Validating block: vector_source_f(1)
> Creating block detail for message_sink(2)
> Creating block detail for vector_source_f(1)
> Allocating new buffer for output 0
> Setting input 0 from edge vector_source_f(1):0->message_sink(2):0
> start_threads: entered
> start_threads: starting 0x6d26f0
> queue
> 0
> msg
> 0
> 4.0
> 200.0
> 800
> wait: entered
> wait: joining thread 0x6d26f0
> wait: join returned