Re: [Discuss-gnuradio] call the work() method

[Marcus Müller]

Hi Xianda,

some of your emails are really hard to read due to your email client
writing non-standard-compliant HTML mail. Could you disable
HTML/multimedia mail?

> What I want to do is that  read symbols from file and perform fft and insert 
> cp and then transmit to the usrp.
ok, thanks for clarifying that!

>Just as the "fft" and "OFDM Cyclic Prefixer" do!

Well, the fft block doesn't read from a file, and ofdm cyclic prefixer does not 
transmit, but I get your point.

> The easy way is use the <gnuradio/fft/fft.h> and 
> <gnuradio/digital/ofdm_cyclic_prefixer.h>;

No!
In GNU Radio, you build flow graphs out of existing blocks, whenever possible. 
So you want to use

[file source] --> [ (I)FFT ] --> [ cyclic prefixer ] --> [ USRP sink ]

by instantiating these blocks, and connecting them to a GNU Radio flow graph. 
Then you let GNU Radio run that flow graph. 
There's no need to write your own block, so far. Actually, you can do this 
without writing a single line of code just by constructing
above flow graph in gnuradio-companion. That will generate the flowgraph  setup 
and starting program in python.

If you need to add more functionality, you usually just add another block to 
this chain, but from what you've said there will be no need to do this.


> But as you said fft_complex_vcc is a block. But now how can i call it in my 
> code?

You don't, see my previous post on calling work().


Greetings,
Marcus



On 31.05.2014 13:53, xianda wrote:
> Hi:<br/>      Thank you so much.<br/>      What I want to do is that  read 
> symbols from file and perform fft and insert cp and then transmit to the 
> usrp.Just as the "fft" and "OFDM Cyclic Prefixer" do!<br/>      The easy way 
> is use the&lt;gnuradio/fft/fft.h&gt; and 
> &lt;gnuradio/digital/ofdm_cyclic_prefixer.h&gt;.But as you said 
> fft_complex_vcc is a block.But now how can i call it in my code?(It's a 
> block.It has work function.)Can i add it's work function in my code?Thank 
> you.<br/>Best regards,<br/>xianda
> At 2014-05-31 07:36:24, "Marcus Müller" <address@hidden> wrote:
>> Hi Xianda,
>>
>>> I just want to write c++ code to realize ("fft" block+"OFDM Cyclic
>> Prefixer").
>>
>> Sorry, I still did not understand. I only understand your C++, so here's
>> my comments:
>>
>> The code you posted has really nothing to do with gr::block;
>> gr::fft:fft_complex is *not* a gr::block, and has no work()!
>> http://gnuradio.org/doc/doxygen/classgr_1_1fft_1_1fft__complex.html
>>
>> Also, I don't see the need to #include
>> <gnuradio/digital/ofdm_cyclic_prefixer.h>. Is this a mistake or was it
>> intentional?
>>
>> fft_complex really just a convenience wrapper around FFTW.
>> I haven't tried to test your code, and you could read() directly into
>> the get_inbuf() buffer, and write directly from your get_outbuf()
>> buffer, but it looks ok.
>>
>> Again: gr::fft:fft_complex is not a block! it is used from within
>> fft_complex_vcc (which is a block).
>> All it does is use the FFTW library to perform FFTs, you can do that
>> yourself without using GNU Radio at all. Only use it when you are
>> developing a GNU Radio program!
>>
>> Greetings,
>> Marcus
>>
>>
>> On 31.05.2014 13:21, xianda wrote:
>>> Hi:
>>> Thank you so much.
>>> I just want to write c++ code to realize ("fft" block+"OFDM Cyclic 
>>> Prefixer").
>>> And I attached my code which just realize ifft but the "OFDM Cyclic 
>>> Prefixer" has it's work function.
>>> #include <fstream>
>>> #include <vector>
>>> #include <gnuradio/gr_complex.h>
>>> #include <gnuradio/fft/fft.h>
>>> #include <gnuradio/digital/ofdm_cyclic_prefixer.h>
>>>
>>> std::vector<std::complex<float> *> buff1(64);//read data
>>> std::vector<std::complex<float> *> buff2(64);//write data
>>>
>>> std::ifstream infile("a.dat",std::ifstream::binary);
>>> std::ofstream outfile("b.dat",std::ofstream::binary);
>>>
>>> int main(){
>>> while(not infile.eof())
>>> {
>>> infile.read((char*)&buff1.front(),buff1.size()*sizeof(std::complex<float>));
>>>
>>> gr::fft::fft_complex *buff=new gr::fft::fft_complex(64,0);
>>> gr_complex *bu=buff->get_inbuf();
>>> memcpy(bu,&buff1.front(),buff1.size()*sizeof(std::complex<float>));
>>> buff->execute();
>>> gr_complex *out=buff->get_outbuf();
>>> memcpy(&buff2.front(),out,buff2.size()*sizeof(std::complex<float>));
>>>
>>> outfile.write((char*)&buff2.front(),buff2.size()*sizeof(std::complex<float>));
>>> }
>>>
>>> infile.close();
>>> outfile.close();
>>> }
>>>
>>> Thank you.
>>> Best regards,
>>> xianda
>>>
>>> At 2014-05-31 06:33:35, "Martin Braun" <address@hidden> wrote:
>>>
>>>
>>>
>>> On 31 May 2014 11:57, "Marcus Müller" <address@hidden> wrote:
>>>> Hi Xianda,
>>>>
>>>>
>>>>>          I know every block should have it's work or general_work 
>>>>> function.And i know it's used by scheduler
>>> For the record, a block that only uses message passing doesn't need a work 
>>> function - not that that's what you're looking for here.
>>>
>>>
>>> M
>>>
>>>
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>>> Discuss-gnuradio mailing list
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>>
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