Re: Problems when passing messages to a source block

The work() functions are for stream handling. You may have already read

https://wiki.gnuradio.org/index.php/Message_Passing

The approach here should be to create a separate thread in your init, and have that thread periodically public a message. There is a Message Strobe block that does this (in C++) and you could take a look at that code as an example.

On Mon, Nov 29, 2021 at 10:06 AM Michelle <mkprojects731@gmail.com> wrote:

Good morning,

I want to generate a source controlled by voltage. Basically, I send messages to a source in order to change its amplitude. I have built a block to generate messages and pass them to the source. To do so, I created an "embedded python block " that generates and transmits a message every second, here is the python code of my block:

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

#The block receives input data (the amplitude of a signal) then generates a message to be passed to a constant source so that the latter modifies its amplitude"

class message_generator(gr.sync_block):
    def __init__(self):
        gr.sync_block.__init__(
            self,
            name="message generator",
            in_sig=[numpy.float32], #amplitude that the signal must have
            out_sig=None
        )
        self.message_port_register_out(pmt.intern('out_port'))
                

    def work(self, input_items, output_items):
       self.msg_port_pub(pmt.intern('out_port'), pmt.cons(pmt.intern("ampl"), pmt.from_double(input_items[0][0])))
       time.sleep(1)
       return 1


when I execute my flowgraph in gnuradio I have the error : self.msg_port_pub(pmt.intern('out_port'), pmt.cons(pmt.intern("ampl"), pmt.from_double(input_items[0][0])))
AttributeError: 'message_generator' object has no attribute 'msg_port_pub' . And I can't understand why if in the  qa_python_message_passing.py (below ) the function message_port_pub is called the same way as I do in mine.

class message_generator(gr.sync_block):
    def __init__(self, msg_interval = 10):
        gr.sync_block.__init__(
            self,
            name="message generator",
            in_sig=[numpy.float32], #amplitude that the signal must have
            out_sig=None
        )
        self.msg_list = []
        #self.message_port_register_in(pmt.intern('in_port'))
        self.message_port_register_out(pmt.intern('out_port'))
        self.msg_interval = msg_interval
        self.msg_ctr = 0
                    

    def work(self, input_items, output_items):
          
        inLen = len(input_items[0])
      
        # Create a new PMT for each input value and put it in the message list
        self.msg_list.append(pmt.from_double(input_items[0][0]))
       
        while self.msg_ctr < len(self.msg_list) and \
                (self.msg_ctr * self.msg_interval) < \
                (self.nitems_read(0) + inLen):
            self.message_port_pub(pmt.intern('out_port'),
                                  pmt.cons(pmt.intern("ampl"),self.msg_list[self.msg_ctr]))
            self.msg_ctr += 1
        return inLen


PLease can you explain to me what is wrong on my code? I even tried to put an attribute "msg_port_pub" when declaring the class but I still have the same error.

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

class message_generator(gr.sync_block):
    def __init__(self):
        gr.sync_block.__init__(
            self,
            name="message generator",
            in_sig=[numpy.float32], #amplitude that the signal must have
            out_sig=None
        )
        d_port= self.message_port_register_out(pmt.intern('out_port'))
        self.msg_port_pub(d_port, self.buildMessage)
      
    def buildMessage(self, data):
       msg = pmt.cons(pmt.intern("ampl"), pmt.from_double(data))
       return msg
        

    def work(self, input_items, output_items):
       messageToSend = builMessage(input_items=[0][0])
       self.msg_port_pub(d_port, messageToSend)
       time.sleep(1)
       return 1


You can find attached my flowgraph and the resulting python code.

Thank you in advance and have a good day.