Re: [Discuss-gnuradio] splitting bits

[Eric Blossom]

On Thu, Jan 10, 2008 at 05:24:06PM -0500, Steven Clark wrote:
> I had looked at those blocks, but can't figure out a way to get them to do
> what I want...
> (2,3,1) into gr.packed_to_unpacked_ss(1,gr.GR_MSB_FIRST) gives:
> (0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
> 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1)
> rather than:
> (1,0,1,1,0,1)
> 
> *bang head on keyboard in search of enlightenment*

You might be able to run unpacked_to_packed followed by
packed_to_unpacked to get what you want.  It's ugly, but you don't
have to write any code ;)

  pack = gr.unpacked_to_packed_ss(2, gr.GR_MSB_FIRST)
  unpack = gr.packed_to_unpacked_ss(1, gr.GR_MSB_FIRST)

Eric



> On Jan 10, 2008 4:51 PM, Eric Blossom <address@hidden> wrote:
> 
> > On Thu, Jan 10, 2008 at 04:43:17PM -0500, Steven Clark wrote:
> > > Hey folks-
> > >
> > > Let's say I have a stream of shorts whose values are one of [0,1,2,3]
> > (in
> > > other words, the bottom 2 bits are active). I want to split these bits,
> > so
> > > that:
> > > [2,3,3,1,0] -> [1,0,1,1,1,1,0,1,0,0], etc.
> > >
> > > What block(s) can help me achieve this?
> >
> >
> > gr_packed_to_unpacked or gr_chunks_to_symbols are probably close to
> > what you're looking for.
> >
> > Eric
> >
> >
> > /*!
> >  * \brief Convert a stream of packed bytes or shorts to stream of unpacked
> > bytes or shorts.
> >  * \ingroup block
> >  *
> >  * input: stream of @I_TYPE@; output: stream of @O_TYPE@
> >  *
> >  * This is the inverse of gr_unpacked_to_packed_XX.
> >  *
> >  * The bits in the bytes or shorts input stream are grouped into chunks of
> >  * \p bits_per_chunk bits and each resulting chunk is written right-
> >  * justified to the output stream of bytes or shorts.
> >  * All b or 16 bits of the each input bytes or short are processed.
> >  * The right thing is done if bits_per_chunk is not a power of two.
> >  *
> >  * The combination of gr_packed_to_unpacked_XX_ followed by
> >  * gr_chunks_to_symbols_Xf or gr_chunks_to_symbols_Xc handles the
> >  * general case of mapping from a stream of bytes or shorts into
> >  * arbitrary float or complex symbols.
> >  *
> >  * \sa gr_packed_to_unpacked_bb, gr_unpacked_to_packed_bb,
> >  * \sa gr_packed_to_unpacked_ss, gr_unpacked_to_packed_ss,
> >  * \sa gr_chunks_to_symbols_bf, gr_chunks_to_symbols_bc.
> >  * \sa gr_chunks_to_symbols_sf, gr_chunks_to_symbols_sc.
> >  */