Dear Seth, Also thanks to your answer. To be clear, is HDLC the same thing what I've searched in google?
High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous data link layer protocol developed by the International Organization for Standardization (ISO). The original ISO standards for HDLC are ... - Wikipedia https://en.wikipedia.org/wiki/High-Level_Data_Link_Control Anyway, thanks again. I'll get that repo and see how it works. :) Regards, Jeon. 2015-10-22 5:43 GMT+09:00 Seth Hitefield <sd...@vt.edu>: > Jeon, > > I was talking with a co-worker and I think I got the stock HDLC > framer/deframer confused with the ones available in gr-framers on the gr-vt > repo: > https://github.com/gr-vt/gr-framers/tree/master/lib > > The framers in gr-framers do produce idle flags when there are no input > messages; I’m not sure about the stock ones. > > — Seth > > > On Oct 21, 2015, at 12.48, Seth Hitefield <sd...@vt.edu> wrote: > > Jeon, > > You could also possibly use the HDLC framer/deframer blocks. That block > produces an idle flag when there are no message inputs. > > -- Seth > > > On 10/21/2015 11:39 AM, Jeon wrote: > > Dear Marcus, > > Thank you for quick and detailed answer. > > I'll check that gr-eventstream as well as fundamentals of GNU Radio you've > described. > > Regards, > Jeon. > > 2015-10-21 22:23 GMT+09:00 Marcus Müller <marcus.muel...@ettus.com>: > >> Hi Jeon, >> >> with gr-eventstream, there's something that already does the "idle time >> padding": >> https://github.com/osh/gr-eventstream/ >> Read Tim's articles, too: >> http://oshearesearch.com/tag/gr-eventstream/ >> >> To answer your question: >> >> 1. Is it allowed to forecast zero item? And does it behave as I expect? >> >> Well, yes, and no :) >> First: your Pad Idle block is a stream source (It doesn't have a stream >> input, only a message input); you don't have to implement a forecast, just >> use a sync block type (or the source block type that gr_modtool offers you >> to generate). >> Generally, it's right to tell GNU Radio you can't produce anything with >> the current input, but: >> stream sources are a little special, as they *never* get input, so from >> GNU Radio's perspective, the input situation can't ever change. So telling >> GNU Radio you can't produce anything will make your flow graph stop. As a >> side note, I've never thought about whether forecast ever gets called on a >> source -- basically, what should that do? There's not ninput_required array >> with nonzero length to be filled with values on a block with no inputs! >> >> 2. If forecasting zero item is possible, willl general_work() be called >> extremely frequently so that other blocks are prevented from being called? >> >> There's no "preventing other blocks from being called". GNU Radio is >> multithreaded, and as long as there's stuff to be done, the other blocks >> will be called until all buffers have run dry. >> >> The point here is that you should just block in your work function if >> you're a source. However, with the modern message passing alone, that's >> impossible, because messages are always delivered when your work is >> currently *not* running. Hence, gr-eventstream takes a queue approach, >> and that works pretty well. >> >> Best regards, >> Marcus >> >> >> >> >> On 10/21/2015 02:53 PM, Jeon wrote: >> >> Consider a flow graph like: <http://i.imgur.com/bNa6YuQ.png> >> http://i.imgur.com/bNa6YuQ.png >> >> >> >> Message source produces a short message. Period is quite long. Thus, >> There should be a long idle time. >> >> I'd like to build a block 'pad idle'. The block pad a predefined sequence >> if the upstream block gives nothing. >> >> I think a prototype would be: >> <https://gist.github.com/gsongsong/d40b85a76ab8e80ae468#file-gistfile1-txt-L11> >> https://gist.github.com/gsongsong/d40b85a76ab8e80ae468#file-gistfile1-txt-L11 >> >> By setting the number of required items to zero in forecast(), >> general_work() will be called even there is no items received. And general >> work() checks the ninput_items and if it is zero, generates some >> idle-padding samples/patterns. Otherwise, it just handles and passess a >> message/samples to downstream. >> >> But it's just my thought. There may be a couple of considerations. >> >> 1. Is it allowed to forecast zero item? And does it behave as I expect? >> 2. If forecasting zero item is possible, willl general_work() be called >> extremely frequently so that other blocks are prevented from being called? >> >> Regards, >> Jeon. >> >> >> _______________________________________________ >> Discuss-gnuradio mailing >> listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> >> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >> >> > > > _______________________________________________ > Discuss-gnuradio mailing > listDiscuss-gnuradio@gnu.orghttps://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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