Re: [Discuss-gnuradio] unable to coerce endpoint

[Yan Nie]

Tom, I really appreciate your reply. I got another question, how to pause the 
system for 5 milliseconds? I'm trying to transmit signal then suspend the 
system without any signal transmission for about 5 milliseconds. The following 
is the part of code that I use to implement this, but it doesn't really work as 
what I expected.


payload_13bit = '\x01\x01\x01\x01\x01\x0'
while(start_flag ==  1)
           msg_13bit = gr.message_from_string(payload_13bit)
           top_block._ls_msgq.insert_tail(msg_13bit)
           time.sleep(0.005)


Could you please help to see what the problem here? Why it cannot stop the 
transmission for 5 milliseconds.


Really appreciate your help.


Thanks,
Yan


On 02/18/11, Tom Rondeau  <address@hidden> wrote:
> 
> On Thu, Feb 17, 2011 at 7:06 PM, Yan Nie <address@hidden> wrote:
> > Dear all,
> >
> > I'm trying to feed the received signal from USRP to a low-pass filter and 
> > sink the filtered signal into a data file.
> >
> > The received signal is in complex format. The receiver is built as:
> >
> > u = usrp.source_c(0)
> > coeffs = gr.firdes.low_pass(1.0, 500e3, 20e3,.5e3,gr.firdes.WIN_HAMMING)
> > lpf = gr.fir_filter_ccf(1,coeffs)
> > dst = gr.file_sink(gr.sizeof_gr_complex,rxlpf.dat)
> > connect(u, lpf, dst)
> >
> > I got a ValueError: unable to coerce endpoint
> >
> > Without the low-pass filter plugged in, if only feed the received signal 
> > into a data file, the system is running well. By checking the output from 
> > the USRP is complex signal and data sank into the data file is complex, 
> > therefore, the input and the output of the low-pass filter are both 
> > selected as complex type. Why does this ValueError show up? How to solve 
> > this error to plugged this low-pass filter in? I really appreciate any idea 
> > related to this.
> >
> > Wish you a great day!
> >
> > Yan
> 
> 
> Yan, I don't know. I copied the above script and it works fine for me.
> I'm a bit confused about two aspects of the code, though. First, you
> have the second input to file_sink as just rxlpf.dat, which looks like
> the name of a file, but it is not quoted. Was this just a
> transcription error?
> 
> Also, in your connect statement, you don't use "self.connect()" or
> "tb.connect()" where 'tb' is a top_block object you have created.
> What's really going on here?
> 
> Have you tried to make this script in the gnuradio companion? It
> should be very simple to put this one together there, and GRC takes
> care of the connections and everything else.
> 
> Tom
>

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Description: Card for "Yan Nie" <ynie3@uwo.ca>