[Discuss-gnuradio] unable to coerce endpoint

[Yan Nie]

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

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