if you still wanna use forecast and general_work then this is how you do it
...
void your_block::forecast(int noutput_items,gr_vector_int
&ninput_items_required){
ninput_items_required[0]=100 * noutput_items;
ninput_items_required[1]=100 * noutput_items;
}
the scheduler will choose the number for noutput_items and it will make sure
that you have the required items on your input streams by calling forecast.
Suppose your output items are a multiple of a specific item e.g. if you
always want 100 items produced each time your general_work() is called then
you have to tell the scheduler that the noutput_items must be a multiple of
100. Call set_output_miltiple() to let the scheduler know this. This is how
it's done,
dsss_spreading_b::dsss_spreading_b(unsigned int
length_PN):gr_block("spreading_b",
gr_make_io_signature(2,2,sizeof(unsigned char)),
gr_make_io_signature(1,1,sizeof(unsigned char))),
d_length_PN(length_PN)
{
set_output_multiple(d_length_PN);
}
for example the above constructor shows a block that has 2 input streams and
one output stream and it calls set_output_multilple which has an integer
parameter d_length_PN passed. The scheduler will make sure that the
noutput_items that it selects will be a multiple of d_length_PN....
if d_length_PN=100 ...then scheduler will choose n*100 output_items ...
where n in an integer.
Look into the examples or the blocks in the gnuradio. Read the comments in
gr_block.h file. This will give you all the information.
Good luck.
On Sun, May 30, 2010 at 9:16 PM, Eric Blossom <[email protected]> wrote:
> On Sun, May 30, 2010 at 01:33:17PM -0700, Zohair wrote:
> >
> > Hello everybody,
> >
> > I'm working on building a block that accepts many inputs (say n) and has
> one
> > output. For a single output item to be generated, 100 samples from each
> > input port should be taken. How can I use forecast() and general_work()
> to
> > serve my purpose? I read somewhere that we never call or modify the
> > parameters explicitly, the scheduler does this instead. But how does the
> > scheduler know that I need 100 samples exactly.
> >
> > Any help is highly appreciated.
>
> No need to use general_work or forecast.
>
> Derive from gr_sync_decimator. There are many examples in
> gnuradio-core/src/lib/general.
>
> Eric
>
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