CODEWITHSUNDEEP
c++gnuradio
Kruncho
Kruncho

Reputation: 205

GNU Radio io_signature

I'm getting into GNU Radio and after I created a new block, in the main class I have a peace of code like this :

square_ff_impl::square_ff_impl()
  : gr::block("square_ff",
              gr::io_signature::make(<+IMIN+>, <+IMAX+>, sizeof (<+ITYPE+>)), // input signature
              gr::io_signature::make(<+OMIN+>, <+OMAX+>, sizeof (<+OTYPE+>))) // output signature
{
    // empty constructor
}

I don't really know exactly what to put in MIN and MAX (even after reading the doc).

Can you give me some examples please ?

Upvotes: 3

Views: 1634

Answers (1)

djanderson
djanderson

Reputation: 603

IMIN - minimum number of acceptable input ports
IMAX - maximum number of acceptable input ports
OMIN - minimum number of acceptable output ports
OMAX - maximum number of acceptable output ports

The documentation talks about it a bit in the IOSignatures portion of the BlocksCodingGuide:

  • The first two parameters are min and max number of ports, this allows blocks to have a selectable number of ports at runtime.

A value of -1 means "unlimited".

As an example of a source block, take a look at the IO signature of the null source block, which takes no input:

null_source_impl::null_source_impl (size_t sizeof_stream_item)
  : sync_block("null_source",
                  io_signature::make(0, 0, 0),
                  io_signature::make(1, -1, sizeof_stream_item))
{
}

For a sink, check out null sink, which has no output:

null_sink_impl::null_sink_impl(size_t sizeof_stream_item)
  : sync_block("null_sink",
               io_signature::make(1, -1, sizeof_stream_item),
               io_signature::make(0, 0, 0))
{
}

And a simple processing blocks, add_ff, which takes unlimited input and produces exactly 1 output stream:

add_ff_impl::add_ff_impl(size_t vlen)
  : sync_block("add_ff",
          io_signature::make (1, -1, sizeof(float)*vlen),
          io_signature::make (1,  1, sizeof(float)*vlen)),
d_vlen(vlen)
{
...

Upvotes: 3

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