Hey Chris, if you reached this far I'm assuming that the new packages have
solved your issues ... Since you're passing normalized values to the DSP you
will need to scale them or they will be converted to zeros when moved to the DSP
float fixed
0.3333 = 0
3.3333 = 3
33.333 = 33
so your scaling factor should be 15. Regarding input/output signature it
allows you to define if the input is normalized (signature = 0) meaning that
the easycom-gpp library would need to scale it before transferring it to the
dsp and the same for the output you'll tell it if it should scale it back to
normalized numbers or should it keep it as fixed point numbers. The motivation
for this is the USRP1 with non-uhd drivers would provide fixed point data
during receive mode and normalized data for transmit mode.
al
src_coeff, 0, 1, 0, 0, 0, 0)
-----Original Message-----
From: Christopher Dean <christopher.d...@ll.mit.edu>
To: Almohanad Fayez <alfa...@aol.com>
Cc: discuss-gnuradio <discuss-gnuradio@gnu.org>
Sent: Wed, Jul 13, 2011 3:37 pm
Subject: gr-dsp Library Block Parameters
Hi Al,
We're trying to use your gr-dsp library and are having difficulty verifying the
output of your DSP.fir_ccf blocks. To allow for easy comparison to the
standard filter type, gr.fir_filter_ccf, we generated a very simple block
diagram in GRC. This consisted of a vector source, an fir_filter_ccf block,
and a file sink. All of the original data and filter taps are the same, but
the outputs are not lining up with their expected values.
I have included the full script file at the bottom of this email. The relevant
calls to the filter constructors are shown in the text.
For instance:
We have:
src = (0.01+0.11j,
0.02+0.22j,
0.03+0.33j,
0.04+0.44j,
0.05+0.55j,
0.06+0.66j,
0.07+0.77j,
0.08+0.88j,
0.09+0.99j)
src_coeff = (0.101, 0.102, 0.103, 0.104, 0.105)
Without scaling (scaling_factor = 0, so scaling by 2^0 = 1):
gr.fir_filter_ccf(1, src_coeff)
This produces output:
0.0010 + 0.0111i
0.0030 + 0.0334i
0.0061 + 0.0671i
0.0102 + 0.1122i
0.0154 + 0.1689i
0.0205 + 0.2255i
0.0257 + 0.2822i
0.0308 + 0.3388i
0.0360 + 0.3954i
What we thought would be the equivalent call using the fir_ccf block is:
self.gr_fir_filter_xxx_0 = dsp.fir_ccf (src_coeff, 0, 1, 0, 0, 0, 0)
This produces output:
0
0
0
0
0
0
0
0
0
With scaling (scaling_factor = 15, so scaling by 2^15):
gr.fir_filter_ccf(1, src_coeff)
The data was manually scaled by 2^15 in MATLAB, producing output:
1.0e+04 *
0.0033 + 0.0364i
0.0100 + 0.1096i
0.0200 + 0.2199i
0.0334 + 0.3677i
0.0503 + 0.5533i
0.0672 + 0.7389i
0.0840 + 0.9245i
0.1009 + 1.1102i
0.1178 + 1.2958i
dsp.fir_ccf (src_coeff, 15, 1, 0, 1, 0, 0)
* output-signature = 1, so we want the output to be have the same scale
factor that it is on the DSP.
This produces output:
1.0e+03 *
0.3350 + 0.3350i
0.3400 + 0.3390i
0.3430 + 0.3440i
0.3470 + 0.3470i
0.3500 - 0.0340i
-0.3650 - 0.1000i
-1.0960 - 0.2000i
-2.1990 - 0.3350i
-3.6770 - 0.5030i
In neither of these cases do the dsp implementation and the gpp implementation
give the same output.
I'm pretty sure that the issue is in my interpretation of your parameters.
I've already been using the online documentation to figure out what the
parameters do, so I know the basic jist of it, but obviously I haven't got it
figured out yet. Could you please explain the use of the scaling_factor,
input_signature, and output_signature parameters in more detail?
Also, for the input_signature parameter to be 0, like it is in the examples
qa_fir_ccf2.py and qa_fir_ccf3.py, doesn't the input need to be normalized? By
my understanding, normalized vectors are unit vectors, so they should have
length 1. But src (above) has length 9, so it's not normalized and the
input_signature parameter should be 1. Is that correct?
Thanks,
Chris
-------------------------------------------------------------------------------
#!/usr/bin/env python
##################################################
# Gnuradio Python Flow Graph
# Title: Top Block
# Generated: Wed Jul 13 11:09:34 2011
##################################################
from gnuradio import eng_notation
from gnuradio import gr
from gnuradio.eng_option import eng_option
from gnuradio.gr import firdes
from optparse import OptionParser
from gnuradio import dsp
class top_block(gr.top_block):
def __init__(self):
gr.top_block.__init__(self, "Top Block")
##################################################
# Variables
##################################################
self.samp_rate = samp_rate = 32000
##################################################
# Blocks
##################################################
self.gr_vector_source_x_0 =
gr.vector_source_c((0.01+0.11j,0.02+0.22j,0.03+0.33j,0.04+0.44j,0.05+0.55j,
0.06+0.66j, .07+0.77j, 0.08+0.88j, 0.09+0.99j), False, 1)
#self.gr_fir_filter_xxx_0 = gr.fir_filter_ccf(1, (0.101, 0.102,
0.103, 0.104, 0.105))
# Uncomment the previous line, comment in the next three lines
to switch from dsp-based to gpp-based filter.
src_coeff = (0.101, 0.102, 0.103, 0.104, 0.105)
dsp.init()
self.gr_fir_filter_xxx_0 = dsp.fir_ccf (src_coeff, 15, 1, 0, 1,
0, 0)
self.gr_file_sink_0 = gr.file_sink(gr.sizeof_gr_complex*1,
"filtertest-dsp2.dat")
self.gr_file_sink_0.set_unbuffered(False)
##################################################
# Connections
##################################################
self.connect((self.gr_vector_source_x_0, 0),
(self.gr_fir_filter_xxx_0, 0))
self.connect((self.gr_fir_filter_xxx_0, 0),
(self.gr_file_sink_0, 0))
def get_samp_rate(self):
return self.samp_rate
def set_samp_rate(self, samp_rate):
self.samp_rate = samp_rate
if __name__ == '__main__':
parser = OptionParser(option_class=eng_option, usage="%prog:
[options]")
(options, args) = parser.parse_args()
if gr.enable_realtime_scheduling() != gr.RT_OK:
print "Error: failed to enable realtime scheduling."
tb = top_block()
tb.start()
raw_input('Press Enter to quit: ')
tb.stop()
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