Re: [Discuss-gnuradio] unable to coerce endpoint

[Tom Rondeau]

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