[Discuss-gnuradio] OFDM GRC block attempt

[Dev Ramudit]

Hello all,

        I'm trying to write an OFDM mod/demod for the gnuradio companion and
I'm running into a problem. I'm following the (now deprecated?) packet
modulator code that was in GRC very closely. I have an OFDMDemod block
which creates the following class when its used:

---

class OFDMDemodHelper(gr.hier_block2):
        """Forward data from ofdm demod to the gr data stream."""
        def __init__(self, item_size, options):
                #create hier block
                gr.hier_block2.__init__(
                        self, 'ofdm_demod',
                        gr.io_signature(1, 1, Complex().get_num_bytes()),
                        gr.io_signature(1, 1, item_size)
                )
                #the message source (handles the output data stream)
                msg_source = gr.message_source(item_size, DEFAULT_QUEUE_LIMIT)
                msgq = msg_source.msgq()
                def callback(ok, payload):
                        if ok: msgq.insert_tail(gr.message_from_string(payload, 
0, item_size,
len(payload)/item_size))
                ofdm_demod = blks.ofdm_demod(
                        fg=self,
                        options=options,
                        callback=callback,
                )
                #connections
                self.connect(msg_source, self)
                self.connect(self, ofdm_demod.head)

---

This is basically the same as the old packet demod code, with a few
small changes for OFDM. Unfortunately, I get the following error:

---

 File "/home/dramudit/work/gnuradio/grc/src/SignalBlockDefs/Packet.py",
line 337, in __init__
    callback=callback,
  File
"/usr/local/lib/python2.4/site-packages/gnuradio/blksimpl/ofdm.py", line
218, in __init__
    options.log)
  File
"/usr/local/lib/python2.4/site-packages/gnuradio/blksimpl/ofdm_receiver.py",
line 56, in __init__
    self.fg.connect(self.chan_filt, self.ofdm_sync)
  File
"/usr/local/lib/python2.4/site-packages/gnuradio/gr/hier_block2.py",
line 46, in connect
    self._connect(points[i-1], points[i])
  File
"/usr/local/lib/python2.4/site-packages/gnuradio/gr/hier_block2.py",
line 50, in _connect
    (dst_block, dst_port) = self._coerce_endpoint(dst)
  File
"/usr/local/lib/python2.4/site-packages/gnuradio/gr/hier_block2.py",
line 61, in _coerce_endpoint
    raise ValueError("unable to coerce endpoint")
ValueError: unable to coerce endpoint

---

Any suggestions as far as fixing this error, or another approach?

Thanks,
Dev