Re: [Discuss-gnuradio] need help getting simple exercise to work

[Matt Ettus]

jmdaniel wrote:
> Hi,
> 
> I've got gnuradio up and running and am now trying to get a better
> understanding of how to use it before beginning more involved
> projects.  I am trying to write a py script that displays an oscope 
> from a PCI-DAS4020/12.  mc4020_fft.py runs and displays the 
> excpected results.  Here's the code that I've peiced together.

>   File "/usr/local/lib/python2.3/site-packages/gnuradio/gr/basic_flow_ 
> graph.py", line 127, in _connect_prim
>     self._check_type_match (src_endpoint, dst_endpoint)
>   File "/usr/local/lib/python2.3/site-packages/gnuradio/gr/basic_flow_ 
> graph.py", line 238, in _check_type_match
>     raise ValueError, 'source and destination data sizes are different '
> ValueError: source and destination data sizes are different
> 
> 
> I would greatly appreciate any help with understanding what is 
> wrong here and how to fix it.

The 4020 returns 16 bit signed integers (shorts).  The scopesink is
expecting floats.  You need to put a  gr.short_to_float () block in
between them.

Matt