Re: Convert PDU message to a PMT message

[Jeff Long]

b_len is defined in the try block, and is out of scope by the time it is checked below.

This code should work. The routine returns in the except clause and b_len is set after the try/except.

import numpy as np
from gnuradio import gr
import pmt
import array

class blk(gr.sync_block):
    def __init__(self):
        gr.sync_block.__init__(
            self,
            name='EPB: Packet to PMT',   # will show up in GRC
            in_sig=None,
            out_sig=None)
        self.message_port_register_in(pmt.intern('msg_in'))
        self.message_port_register_out(pmt.intern('msg_out'))
        self.set_msg_handler(pmt.intern('msg_in'), self.handle_msg)

    def handle_msg(self, msg):
        _debug = 0          # set to zero to turn off diagnostics
        try:
            buff = pmt.to_python(pmt.cdr(msg))
        except Exception as e:
            gr.log.error("Error with message conversion: %s" % str(e))
            return
       
        b_len = len (buff)
        if (_debug):
            print ("new_val =", buff, b_len)
        if (b_len != 52):
            self.message_port_pub (pmt.intern('msg_out'), pmt.cons(pmt.PMT_NIL,pmt.to_pmt(buff)))
        elif ((buff[0] != 37) and (buff[51] != 93)):
            self.message_port_pub (pmt.intern('msg_out'), pmt.cons(pmt.PMT_NIL,pmt.to_pmt(buff)))

On Wed, Jul 5, 2023 at 6:11 PM Barry Duggan <barry@dcsmail.net> wrote:

I would like to receive a PDU message containing a string using an Embedded Python Block and, after discarding certain messages, send a PMT message with that string to the output message port. My efforts so far have not produced a valid PMT format. My current code is:

```

import numpy as np

from gnuradio import gr

import pmt

import array

class blk(gr.sync_block):

    def __init__(self):

        gr.sync_block.__init__(

            self,

            name='EPB: Packet to PMT',   # will show up in GRC

            in_sig=None,

            out_sig=None)

        self.message_port_register_in(pmt.intern('msg_in'))

        self.message_port_register_out(pmt.intern('msg_out'))

        self.set_msg_handler(pmt.intern('msg_in'), self.handle_msg)

    def handle_msg(self, msg):

        _debug = 0          # set to zero to turn off diagnostics

        try:

            buff = pmt.to_python(pmt.cdr(msg))

            b_len = len (buff)

        except Exception as e:

            gr.log.error("Error with message conversion: %s" % str(e))

        if (_debug):

            print ("new_val =", buff, b_len)

        if (b_len != 52):

            self.message_port_pub (pmt.intern('msg_out'), pmt.cons(pmt.PMT_NIL,pmt.to_pmt(buff)))

        elif ((buff[0] != 37) and (buff[51] != 93)):

            self.message_port_pub (pmt.intern('msg_out'), pmt.cons(pmt.PMT_NIL,pmt.to_pmt(buff)))

```

Any help will be appreciated!

---

Barry Duggan