Hi Yan,
You should only pass only one value in the second member. Try :
pmt.cons(pmt.intern("freq"), pmt.to_pmt(2.4e9))
Cheers,
Timothée.
2016-03-15 12:14 GMT+01:00 Yan Huang <eexy...@nottingham.ac.uk>:
> Hi Martin,
>
> Thank you, it works well. But I want to change the frequency
> automatically, so I change the frequency to array like:
>
>
> pmt.cons(pmt.string_to_symbol("freq"),pmt.to_pmt(numpy.array([2.4e9,2.45e9],dtype=numpy.float32)))
>
> and I also import numpy in GNU Radio, but it comes up with error :
>
> thread[thread-per-block[10]: <block gr uhd usrp source (1)>]:
> pmt_to_double: wrong_type : #[2.4e+09 2.44999987e+09]
>
> Thanks,
>
> Yan
>
> -----Original Message-----
> From: discuss-gnuradio-bounces+eexyh22=nottingham.ac...@gnu.org [mailto:
> discuss-gnuradio-bounces+eexyh22=nottingham.ac...@gnu.org] On Behalf Of
> Martin Braun
> Sent: 15 March 2016 00:43
> To: discuss-gnuradio@gnu.org
> Subject: Re: [Discuss-gnuradio] Change frequency in USRP source
> automatically
>
> Yan,
>
> simply convert "freq" and your frequency to a PMT before passing into
> cons().
>
> Cheers,
> Martin
>
> On 03/14/2016 03:44 PM, Yan Huang wrote:
> > Hi Martin,
> >
> > Thank you for your kind reply. But I'm still comfused that I already
> have to input in pmt::cons("freq",2.4e9), cause in the manual it said:
> >
> > pmt::cons(KEY, VALUE): This format is useful for commands that take a
> single value. Think of KEY and VALUE as the argument name and value,
> respectively. For the case of the QT GUI Frequency Sink, KEY would be
> "freq" and VALUE would be the new center frequency in Hz.
> >
> > Could you please give me an exmaple about it?
> >
> > Thank you a lot,
> >
> > Yan
> > ________________________________________
> > From: discuss-gnuradio-bounces+eexyh22=nottingham.ac...@gnu.org
> > [discuss-gnuradio-bounces+eexyh22=nottingham.ac...@gnu.org] on behalf
> > of Martin Braun [martin.br...@ettus.com]
> > Sent: 14 March 2016 17:18
> > To: discuss-gnuradio@gnu.org
> > Subject: Re: [Discuss-gnuradio] Change frequency in USRP source
> > automatically
> >
> > Yan,
> >
> > check the PMT manuals. cons() takes 2 PMTs as input.
> >
> >
> > Cheers,
> > Martin
> >
> > On 03/14/2016 09:09 AM, Yan Huang wrote:
> >> Hi all,
> >>
> >>
> >>
> >> I want to change the frequency in "USRP source" automatically, for
> >> example 2.37GHz-2.43GHz with each time stepping 2MHz.
> >>
> >>
> >>
> >> 1. As you know, the USRP source has an input message port, so I want
> >> to connect it to a "Message strobe" to control the frequency change.
> >> But after I see [1][2], I write PMT type commands in "Message PMT"
> >> in "Message Strobe" as:
> >>
> >> pmt::cons("freq",2.4e9)
> >>
> >> it comes up error "invalid syntax(<string>,line 1)", so I don't know
> >> how to further stepping the frequency.
> >>
> >> 2. If I use the "Message Strobe" to define frequency, what can I put
> >> in the "frequency" in "USRP source" block? Put it as 0?
> >>
> >>
> >>
> >> [1] https://gnuradio.org/doc/doxygen/page_uhd.html#uhd_command_syntax
> >>
> >> [2]
> >> https://gnuradio.org/doc/doxygen/page_msg_passing.html#msg_passing_co
> >> mmands
> >>
> >>
> >>
> >> Many thanks ,
> >>
> >>
> >>
> >> Yan
> >>
> >>
> >>
> >>
> >>
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