Issue about message port of grextras

GNU Radio
#1

Hi all,

Recently I am learning the grextras project. I am confused about the
message port which is designed in grextras.
Why will we not get a error when the message ports do not connect to
other message ports? I thought those port actually is data stream ports,
so they should be connected to other ports.

Best regards,
Damon

#2

On Tue, Apr 22, 2014 at 5:09 AM, Damon [email protected] wrote:

Damon,
grextras is an external project from GNU Radio and not related to the
core
functionality.

But GNU Radio’s message passing structure does not require connections.
It’s a publish-subscribe model, and a block will publish a message
regardless of whether or not another block is subscribed and listening.

Tom

#3

Hi Tom,

Thanks for you reply.

I am wondering why the data stream ports of byte or integer 8 could be
disconnected by other ports.

Here is an example. The connecting code is commented out, but we can run
this program without getting a error.

#!/usr/bin/env python
##################################################

Gnuradio Python Flow Graph

Title: Top Block

Generated: Thu Apr 24 11:57:08 2014

##################################################

from gnuradio import blocks
from gnuradio import eng_notation
from gnuradio import gr
from gnuradio.eng_option import eng_option
from gnuradio.filter import firdes
from optparse import OptionParser

class top_block(gr.top_block):

def __init__(self):
    gr.top_block.__init__(self, "Top Block")

    ##################################################
    # Variables
    ##################################################
    self.samp_rate = samp_rate = 32000

    ##################################################
    # Blocks
    ##################################################
    self.blocks_null_source_0 = blocks.null_source(gr.sizeof_char*1)
    self.blocks_null_sink_0 = blocks.null_sink(gr.sizeof_char*1)

    ##################################################
    # Connections
    ##################################################
    #self.connect((self.blocks_null_source_0, 0),

(self.blocks_null_sink_0, 0))

QT sink close method reimplementation

def get_samp_rate(self):
    return self.samp_rate

def set_samp_rate(self, samp_rate):
    self.samp_rate = samp_rate

if name == ‘main’:
parser = OptionParser(option_class=eng_option, usage="%prog:
[options]")
(options, args) = parser.parse_args()
tb = top_block()
tb.start()
raw_input('Press Enter to quit: ')
tb.stop()
tb.wait()

Best regards,
Damon

2014-04-23 21:46 GMT+08:00 Tom R. [email protected]:

#4

On Thu, Apr 24, 2014 at 12:01 AM, Damon [email protected]
wrote:

#!/usr/bin/env python
from gnuradio.filter import firdes
self.samp_rate = samp_rate = 32000
#self.connect((self.blocks_null_source_0, 0),

Best regards,
Damon

I really don’t understand the question. Why do you think this behavior
is
wrong? There are no blocks in the flowgraph; that’s not a condition to
say
it won’t run. When you hit start, it’ll try to start all threads; there
are
none, so it will immediately exit. The raw_input is a Python thing, so
that
will continue to block.

Tom

#5

I got it. If the message port defined in grextras is disconnected, the
message sink or source block will not in the flowgraph.
Thanks Tom.

Best regards,
Damon