Hi All: I am sorry to bother the list with such newbie questions, but I am climbing the gnuradio and C++ learning curve. Hope you don’t mind!
I am working on a new OOT block that is similar to the Repeat block, but allows
for a variable interpolation rate. I followed the Guided Tutorials (thanks
Marcus et al) and the new block, which I called “repeat_dynamic” appears to be
working, sort of… What I notice is that a simple flowgraph to testing purposes
grinds to a halt. I noticed this while debugging my <callback> function that
resets the appropriate interpolation variable, called d_interp.
Here is my flowgraph, with the properties of the new block shown. Note that
“Interpolation is set to variable ‘z’, which is controlled through a Chooser:
Here are my callback and work() functions. work() is essentially copied from
the standard Repeat block. I have added some debug print statements to the
console to try to figure out what is going on:
void
repeat_dynamic_impl::set_interp(int interp)
{
d_interp = interp;
gr::sync_interpolator::set_interpolation(d_interp);
std::cout << "set_interp: d_interp now equals " << d_interp << "\n";
}
int
repeat_dynamic_impl::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const char *in = (const char *) input_items[0];
char *out = (char *) output_items[0];
// Do <+signal processing+>
std::cout << "work: noutput_items = " << noutput_items << "\n";
std::cout << "work: d_interp = " << d_interp << "\n\n";
for (int i = 0; i < noutput_items/d_interp; i++) {
for (int j = 0; j < d_interp; j++) {
memcpy(out, in, d_itemsize);
out += d_itemsize;
}
in += d_itemsize;
}
// Tell runtime system how many output items we produced.
return noutput_items;
}
My callback function gets triggered correctly when I change the value of
variable ‘z’ through the flowgraph Chooser. I see console messages “d_interp
now equals X”. So far so good.
The problem is that the input 0 of the Time Sink doesn’t change to reflect the
new value of d_interp. I added two more debug print statements to work() to
see what’s going on. I know this may not be advisable given assumed
complexities in the scheduler, but I wanted to do something to try to solve my
own problem. The entire flowgraph appears to work for awhile, but
noutput_items moves towards 0 and the whole process grinds to a halt.
I tried reducing the sampling rate to 1000, and then I CAN see changes in the
Time Sink and the in0 trace getting updated as I click various alternate ‘z’
values in the Chooser, but soon the debug messages from work() cease and
everything seems to grind to a halt with a low value (~10) for noutput_items.
The graph is still running, however, as subsequent clicks in the Chooser,
changing ‘z’, still result in a console message showing that d_interp has
indeed been updated. I just never see another update from the two std::cout
statements in work().
As it works at low sample rates for awhile (max a few seconds), I think that
the basic functionality is okay. I am missing a C++ or gnuradio nuance of some
type.
So, I am guessing that I am doing something wrong possibly in the way I call
sync_interpolator::set_interpolation(d_interp) in my callback function.
Newbie deficiencies are evident and I am turing to the list for some
suggestions.
I am using Ubuntu 14.04 and the latest gnuradio, built through the
build-bnuradio script.
Thanks in advance,
Kevin
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