Re: [Discuss-gnuradio] INFO: Detected an invalid packet at item INFO: Parser returned #f

[Bastian Bloessl]

> On 30 Jan 2015, at 14:00, zs <address@hidden> wrote:
> 
> Hi Bastian:
>                  Thank you so much.I use the ofdm example,and I think maybe 
> the crc is wrong as you said,thank you.
>                  Can you give me some advices to avoid these warning?Thank 
> you so much.

The fact that your CRC is not correct just means that *something* does not 
work. This can have a lot of reasons. For example you could try different gain 
settings. Also assert that the samples that you stream to your USRP are in the 
interval [-1, 1].

If that doesn’t solve your problem you can debug your flow graph with graphical 
sinks and check if the signal looks as expected.

> 
> 
> 
> At 2015-01-30 00:43:12, "Bastian Bloessl" <address@hidden
> > wrote:
> >Hi,
> >
> >On 01/29/2015 03:13 PM, zs wrote:
> >> Can you tell me,for general,in which circumstance,the packet header maybe 
> >> corrupt?
> >
> >This is very hard to tell since I don't know what you are doing. I guess 
> >you use a header_formatter in your flow graph and (for whatever reason) 
> >its header_parse method returns false.
> >
> >For example with the default header it looks like this happens if the 
> >CRC is not correct
> >
> >https://github.com/gnuradio/gnuradio/blob/master/gr-digital/lib/packet_header_default.cc#L132
> >
> >
> >>
> >>
> >> At 2015-01-29 20:44:13, "Bastian Bloessl" <
> address@hidden
> > wrote:
> >>>Hi,
> >>>
> >>>On 01/29/2015 01:03 PM, zs wrote:
> >>>> Detected an invalid packet at item INFO: Parser returned #f".
> >>>> The answer may be "RF settings are distorting your signal" or others.I
> >>>> want to ask a question.Which block in gnuradio give us this hint.Where
> >>>> is the source code of the block?And have someone can help me to explain
> >>>> this problem more details?Why will have this error/warning?
> >>>
> >>>
> >>>~/src/gnuradio >> ack-grep -C 3 "an invalid packet"
> >>>gr-digital/lib/packet_headerparser_b_impl.cc
> >>>80-      );
> >>>81-
> >>>82-      if (!d_header_formatter->header_parser(in, tags)) {
> >>>83:        GR_LOG_INFO(d_logger, boost::format("Detected an invalid packet 
> >>>at
> >>>item %1%") % nitems_read(0));
> >>>84-        message_port_pub(msg_port_id, pmt::PMT_F);
> >>>85-      } else {
> >>>86-        pmt::pmt_t dict(pmt::make_dict());
> >>>
> >>>
> >>>I guess your packet header is corrupt.
> >>>
> >>>Best,
> >>>Bastian
> 
> 
> 
> 
> 

--
Dipl.-Inform. Bastian Bloessl
Distributed Embedded Systems Group
University of Paderborn, Germany
http://www.ccs-labs.org/~bloessl/