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

[Marcus Müller]

Hi!

The gr-uhd USRP sink can represent multiple USRPs at once.
If you have a recent GNU Radio version, in gnuradio-companion your "UHD:
USRP Sink" block will have a "Documentation" tab.
There is an example that specifies two USRP addresses. This will
automatically enable you to transmit the contents of both files
simultaneously [1].
You should start with the gnuradio-companion, which will generate
easy-to-read Python code.
Usually, you don't need to write your own blocks to interface with USRPs.

Greetings,
Marcus

[1] "Simultaneously" does not mean "coherently"!

On 31.05.2014 14:48, xianda wrote:
> Hi:
>      Thank you so much for your kindly reply.
>      Sorry for my poor English.
>      The reason why i directly write the c++ code is that I want to use the 
> uhd to control my two usrps send simultaneously.
>      The aim i want to reach is that read symbol from file and perform ifft 
> and insert cp and then transmit.Just like you write:
>      [file source 1] --> [ (I)FFT ] --> [ cyclic prefixer ] --> [ USRP sink 1]
> [file source 2] --> [ (I)FFT ] --> [ cyclic prefixer ] --> [ USRP sink 2]
> I can control them simutanously.Use some class like uhd::usrp::multi_usrp.
> Which is the best way to realize it?Use the c++ or write python flow 
> graph?Thanks.
> Thank you so much.
> Best regards,
> xianda
>
>
>
>
>
>
>
>
> At 2014-05-31 08:25:53, "Marcus Müller" <address@hidden> wrote:
>> 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
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Discuss-gnuradio mailing list
>>>>> address@hidden
>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>>>> _______________________________________________
>>>> Discuss-gnuradio mailing list
>>>> address@hidden
>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio