Re: Problems when passing messages to a source block

[Michelle]

Good morning Jeff,

yes "data" was a double, but I already understood the problem (there was a discussion about that).  The source signal block expects the messages to be in dictionary format not pairs. Finally it works, thank you for your help :)

Here is the final code:

from gnuradio import gr, blocks
from threading import Thread
import pmt
import numpy
import time

class messageGenerator(gr.sync_block):
    def __init__(self, input=[0.5,0,1.5,0]):
        gr.sync_block.__init__(
            self,
            name="message generator",
            in_sig=None,
            out_sig=None
        )
        self.message_port_register_out(pmt.intern('out_port'))
        self.input = input
        self.finished = False
        self.thread = None
        self.message_list = self.handler(self.input)
       
    def handler(self, aList):
         pmt_dict = pmt.make_dict()
         msg_list = []
         for i in aList:
           pmt_dict = pmt.dict_add(pmt_dict, pmt.intern("ampl"), pmt.from_double(i))
           msg_list.append(pmt_dict)
         return msg_list  
                          
    def start(self):   
        self.finished = False
        self.thread = Thread(target=self.run, args=(self.message_list, ), daemon=True)
        self.thread.start()
        return True        
       
    def stop(self):   
        self.finished = True
        self.thread.terminate()
        self.thread.join()
        return True               

    def run(self, data):
        counter = 0
        while(self.finished==False):
         for i in data:
          self.message_port_pub(pmt.intern('out_port'), i)   
          time.sleep (1)
        return len(data)

On 2021-12-06 7:07 p.m., Jeff Long wrote:

Is "data" a double? Thread() passes "args" to self.run() ...

On Mon, Dec 6, 2021 at 6:32 PM Michelle <mkprojects731@gmail.com> wrote:

Hi Jeff,

Thank you very much, all this time I didn't realize.

Now I have the following error:Warning: failed to XInitThreads()
thread[thread-per-block[0]: <block sig_source(5)>]: pmt_car: wrong_type : ampl",

there is something bad with the red marked line (below) , but according to what is explained in the wiki that' s how commands should be encoded. And the doc said that the key for the amplitude is "ampl"

Please could you review the line marked in red and tell me what is wrong?

class messageGenerator(gr.sync_block):
    def __init__(self, msg=1):
        gr.sync_block.__init__(
            self,
            name="message generator",
            in_sig=None,
            out_sig=None
        )
        self.message_port_register_out(pmt.intern('out_port'))
        self.msg = msg
        self.finished = False
        self.thread = None
                          
    def start(self):   
        self.finished = False
        self.thread = Thread(target=self.run, args=(self.msg, ), daemon=True)
        self.thread.start()
        return True
       
    def stop(self):   
        self.finished = True
        self.thread.stop()
        self.thread.join()
        return True


    def run(self, data):
        while(self.finished == False):
         msgToSend = pmt.cons(pmt.intern("ampl"), pmt.from_double(data))
         self.message_port_pub(pmt.intern('out_port'), msgToSend)      
         time.sleep (1)
        return (1)       

m=messageGenerator(3)
m.start()

On 2021-12-06 5:14 p.m., Jeff Long wrote:

It is message_port_pub, not msg_port_pub, if that helps.

On Mon, Dec 6, 2021 at 4:48 PM Michelle <mkprojects731@gmail.com> wrote:

Good evening,

I wonder where the function msg_port_pub is defined, I do not find it anywhere.

I ask because the error "can't interpret source code: 'messageGenerator' object has no attribute 'msg_port_pub' " persists.  I have implemented a handler that calls the function but it doesn't fix the issue. So I would like to try 2 things:

1) define the original function in my embedded python block and invoke it. And if it doesn't work,

2) invoke the original C++ function with pybinds.

Thanks you and have a nice evening.

On 2021-12-01 11:26 a.m., Michelle wrote:

Good morning Jeff,

I didn't write you yesterday because the code doesn't work yet as I want and I was trying to understand why. I don't have any error message but when I execute my flowgraph the value of the amplitude doesn't change and I have the warning "failed to XInitThreads()".I have almost always this warning in gnuradio so it does not worry me for the moment. below is my code:

from gnuradio import gr, blocks
from threading import Thread
import pmt
import numpy
import time

class messageGenerator(gr.sync_block):
    def __init__(self, msg=1, period=1):
        # calling init of a parent class
        gr.sync_block.__init__(
            self,
            name="message generator",
            in_sig=None,
            out_sig=None
        )
        d_port = self.message_port_register_out(pmt.intern('out_port'))
        self.msg = msg
        self.period = period
        self.finished = False
       
    def start(self):   
        self.finished = False
        a_thread = Thread(target = self.run, args =(self.msg, ))
        return True
          
    def stop(self):
       self.finished = True
       #a_thread.stop()
       #a_thread.join()
       return True
      
    def run(self, data):
        msgToSend = pmt.cons(pmt.intern("ampl"), pmt.from_double(data))
        self.msg_port_pub(d_port, msgToSend)
        time.sleep (period)
        return (1)
       
m = messageGenerator(3,1) 
m.start()
m.stop()

When I compare your code with mine I realize some of my mistakes:
1) in the start() function I don't start the thread. It is necessary to add thread.start()
2) same error in the stop function.
3) thread must be an attribute. This answers a problem I had when I tried to stop and join the thread in the stop function.

I'll try it all and get back to you.

thank you!

   

On 2021-11-30 4:14 p.m., Jeff Long wrote:

Ha! No, not emailing myself, just a user who was replying directly. But to continue my conversation (hopefully with the OP), here is some working code. It does a print() because I didn't get around to actually sending a pmt as a message, but you get the idea. Picture of flowgraph attached.

import threading
import time

import numpy as np
from gnuradio import gr
import pmt

class blk(gr.sync_block):
   
    def __init__(self, val=0):
        gr.sync_block.__init__(
            self,
            name='Show Value',
            in_sig=[],
            out_sig=[]
        )
        self.message_port_register_out(pmt.intern("msgout"))
        self.val = val
        self.thread = None
        print('init')

    def start(self):
        print('start')
        self.stopit = False
        self.thread = threading.Thread(target=self.run, daemon=True)
        self.thread.start()
        return True

    def stop(self):
        print('stop')
        self.stopit = True
        self.thread.join()
        return True

    def set_val(self, val):
        self.val = val

    def run(self):
        while(not self.stopit):
            print(f'val={self.val} (would send as message)')
            time.sleep(1)

On Tue, Nov 30, 2021 at 2:13 AM Marcin Puchlik <m.puchlik@is-wireless.com> wrote:

Jeff,

Are you mailing with yourself?

wt., 30 lis 2021 o 00:46 Jeff Long <willcode4@gmail.com> napisał(a):

Sounds good. Only look at the C++ to figure out the general idea. I'd learn Python threading first in a standalone program so you're not learning (debugging) GR and python threading at the same time. Good luck - let us know how it goes.

Also, please respond to the mailing list so everyone can benefit from the conversation.

On Mon, Nov 29, 2021 at 5:11 PM Michelle <mkprojects731@gmail.com> wrote:

Hi Jeff,

thank you for your help and sorry for the delay, I was in class.

it is now that I start to work on it. My first step is to master how the c++ code of the strobe message block work, specially the functions:

-bool message_strobe_impl::start()

-bool message_strobe_impl::stop()

-void message_strobe_impl::run()

Then I will implement the python version following your advice. I will write to you to show you the result.

Once again thank you, I was really lost.

Have a good afternoon.

OK, it does work, as long as there is a message port defined and connected in a flowgraph. I was trying too simple an example. You would do your thread management in the start() and stop() functions.

"""
Embedded Python Blocks:

Each time this file is saved, GRC will instantiate the first class it finds
to get ports and parameters of your block. The arguments to __init__  will
be the parameters. All of them are required to have default values!
"""

import numpy as np
from gnuradio import gr
import pmt

class blk(gr.sync_block):  # other base classes are basic_block, decim_block, interp_block
    """Embedded Python Block example - a simple multiply const"""

    def __init__(self):  # only default arguments here
        """arguments to this function show up as parameters in GRC"""
        gr.sync_block.__init__(
            self,
            name='Embedded Python Block',   # will show up in GRC
            in_sig=[],
            out_sig=[]
        )
        self.message_port_register_out(pmt.intern("msgout"))
        print('init')

    def start(self):
        print('start')
        return True

    def stop(self):
        print('stop')
        return True

On Mon, Nov 29, 2021 at 2:13 PM Jeff Long <willcode4@gmail.com> wrote:

Issue submitted: https://github.com/gnuradio/gnuradio/issues/5358

On Mon, Nov 29, 2021 at 1:58 PM Jeff Long <willcode4@gmail.com> wrote:

It does not seem that python blocks can override start() and stop(), which they should be able to do. So, don't go too far down that path. I do not see anywhere in the code where this is used or would have been caught.

The embedded blocks are easier, be beware that GRC calls the init function to learn about the block. Therefore, you don't want any action taken as a result of a call to init, for instance spawning a thread and starting to send messages. Embedded python block are sort of a toy that turned out to be useful. In general, an OOT is a better idea, but an embedded block can work if it's simple enough.

Maybe someone else has figured this out. With just a quick look, I don't see how a Message Strobe kind of block can be implemented in python without start() and stop().

Here's kind of a hack: make a python block with a message handler that gets a periodic strobe from the existing Message Strobe block. In the handler, send out the message that you would have sent in the thread.