Re: [Discuss-gnuradio] hier_block2 syntax question

[Dev Ramudit]

Johnathan Corgan wrote:
> Steven Clark wrote:
>
> > Ok, thanks Johnathan. Can we fake it in the meantime by throwing in a
> > "nop" block?
>
> gr.nop doesn't copy from input to output; you want gr.kludge_copy or
> gr.skiphead(0).

I ran into the same problem as the original poster a little while ago. 
I'm trying to convert the OFDM blocks to hier2, and testing the new 
hier2 TX path I wrote with the old hier RX path worked fine. The RX part 
of OFDM is a bit more complicated, with more areas that the input is 
connected to various blocks. I was using the old gr.add_const_cc(0) to 
split the input but all the blocks after it seemed to receive no data 
(according to the logging on ofdm_sync_pnac and ofdm_receiever).

Using gr.kludge_copy or skiphead seems to have the same problem, so I 
moved up in the hierarchy to the ofdm.ofdm_demod block. There I changed:

        self.connect(self, self.ofdm_recv)

        self.connect((self.ofdm_recv, 0), (self.ofdm_demod, 0))
        self.connect((self.ofdm_recv, 1), (self.ofdm_demod, 1))


to:

        self.kludge = gr.kludge_copy(gr.sizeof_gr_complex)
        self.connect(self, self.kludge)

        self.connect(self.kludge, gr.file_sink(gr.sizeof_gr_complex, 
"ofdm_kludge.dat"))

        self.connect(self.kludge, self.ofdm_recv)
        self.connect((self.ofdm_recv, 0), (self.ofdm_demod, 0))
        self.connect((self.ofdm_recv, 1), (self.ofdm_demod, 1))

To try and log what's getting passed into ofdm_recv. However running the 
changed version produces:

terminate called after throwing an instance of 'std::runtime_error'
  what():  fft_filter_ccc(5): insufficient connected input ports (2 
needed, 1 connected

The first block in ofdm_recv is this fft_filter_ccc, and it is connected 
directly from the input of the hier2 block. Changing back to the 
previous version of the code does not produce this error, but no data 
reaches the logging functions in ofdm_receiver. The .cc file of 
fft_filter_ccc seems to show that it only takes one input, so I'm 
confused as to why I'm receiving that error.

If anyone is interested, I've uploaded my current progress to
http://155.246.68.205/filebin/ofdmblks2.tar.gz

The benchmark_tx/rx files have been modified to use the local copies of 
the ofdm blocks, so it can be run in place.

Thanks!
Dev