Hi Cristian, you need to subscribe a /handler/ to the message port. See:
https://wiki.gnuradio.org/index.php/Guided_Tutorial_Programming_Topics#5.3.2_Adding_Message_Passing_to_the_Code It's absolutely up to you what kind of PMT you're publishing over a message port, but it's canonical to have a PMT dict that maps pmt::mp("propertyname") -> pmt::whateversuitsyourproperty. As an example, see what the gr-uhd blocks accept [1] Best regards, Marcus [1] https://gnuradio.org/doc/doxygen/page_uhd.html#uhd_command_syntax On 06/26/2017 07:35 PM, Cristian Rodríguez wrote: > Hi all, > > I'm not sure about how to read and write PMT ports from and to local > variables. I'm going to expose what i'm doing, and if someone can help > me i would be very greatful. > > I've created an input and an output of PMT type. > > message_port_register_in(pmt::pmt_t in_threshold) > message_port_register_out(pmt::pmt_t out_threshold) > > Now i want to read the port, and save the data in a local variable, do > operations with that variable, and later write it in the output, > > I create the variables, > > double d_threshold; > pmt::pmt_t target; > > *I read it, I don't know how to do it. But I suppose: > > * > message_port_sub(pmt::pmt_t > <https://gnuradio.org/doc/doxygen/namespacepmt.html#ab4b70d9293452eb74dd07c670e6811fa> > in_threshold,pmt::pmt_t > <https://gnuradio.org/doc/doxygen/namespacepmt.html#ab4b70d9293452eb74dd07c670e6811fa> > target); > d_threshold= pmt::to_double > <https://gnuradio.org/doc/doxygen/namespacepmt.html#a0f58166fe9f449249f5de7dc7b3ab754>(target); > > And, I think i can write it as follows: > > msg=pmt::from_double > <https://gnuradio.org/doc/doxygen/namespacepmt.html#ad20c287c509e8470d03d1c8e97fea12d>(d_threshold); > message_port_pub(pmt::pmt_t > <https://gnuradio.org/doc/doxygen/namespacepmt.html#ab4b70d9293452eb74dd07c670e6811fa> > out_threshold,pmt::pmt_t > <https://gnuradio.org/doc/doxygen/namespacepmt.html#ab4b70d9293452eb74dd07c670e6811fa> > msg); > > What do you think, i've seen several examples, and they do this, > message_port_pub(pmt::mp("symbols"), pmt::cons(pmt::make_dict(), > pmt::init_c32vector(48, symbols))); > > But I don't understand why it is necessary to use pmt::make_dict(). > > Thanks in advance. > > Best regards, > > Cristian > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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