Re: [Discuss-gnuradio] I & Q channels in source module

[Tom Rondeau]

On Thu, Apr 23, 2015 at 3:09 PM, Yile Ku <address@hidden> wrote:

I am writing a source module/block and I generate 16 bit signed I and Q values.  There is first a 16 bit I value then a 16 bit Q value repeated 1024 times. 

In my source module I have:

    usbradio_impl::usbradio_impl()
      : gr::sync_block("usbradio",
              gr::io_signature::make(1, 1, sizeof(short)),
              gr::io_signature::make(1, 1, sizeof(short)))
    {
               state = 0;
               cnt = 0;
               set_max_noutput_items(1);
               set_max_output_buffer(2);
    }

Why are you using set_max_noutput_items and set_max_output_buffer like this? Those numbers don't make any sense. These are fairly advanced features that you should only use if you know /exactly/ what you are doing with them. These lines will make assumptions about the flow of data that will likely hurt how you process things in the work function.

Tom

 

    /*
     * Our virtual destructor.
     */
    usbradio_impl::~usbradio_impl()
    {
    }

    int
    usbradio_impl::work(int noutput_items,
                          gr_vector_const_void_star &input_items,
                          gr_vector_void_star &output_items)
    {
        short  *out = (short *) output_items[0];

        // Do <+signal processing+>
        stuff_output(out);

        // Tell runtime system how many output items we produced.
        return 1024;
    }

The stuff_output(out) function will stuff an I value then a Q value 512 times.  

Is that the correct way to present I & Q values?

Thx,

Y-

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