Decoding of a transmit signal file from matlab

GNU Radio
1

Hi,

I try to demodulate a file of a transmit signal file (from matlab). But
I
can not get the correct message. Therefore I need your suggestion.

Below is the code

Thanks
Makmur

#!/usr/bin/env python
from gnuradio import gr
from gnuradio.eng_option import eng_option
from grc_gnuradio import wxgui as grc_wxgui
from optparse import OptionParser
import wx

class coba_demod(grc_wxgui.top_block_gui):

def init(self):
grc_wxgui.top_block_gui.init(self, title=“Demodulasi transmit
signal”)

##################################################

Variables

##################################################
self.samp_rate = samp_rate = 32000

##################################################

Blocks

##################################################
self.gr_diff_decoder_bb_0 = gr.diff_decoder_bb(5)
self.gr_file_sink_0 = gr.file_sink(gr.sizeof_char1,
“/home/makmur/datacoba”)
self.gr_file_source_0 = gr.file_source(gr.sizeof_char1,
“/home/makmur/transmit_signal.mat”, False)
self.gr_throttle_0 = gr.throttle(gr.sizeof_char*1, samp_rate)

##################################################

Connections

##################################################
self.connect((self.gr_file_source_0, 0), (self.gr_throttle_0, 0))
self.connect((self.gr_throttle_0, 0), (self.gr_diff_decoder_bb_0, 0))
self.connect((self.gr_diff_decoder_bb_0, 0), (self.gr_file_sink_0, 0))

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()
tb = coba_demod()
tb.Run(True)

2

Makmur,

gnuradio and python cannot read from matlab .mat files directly. If you
want
to construct a signal in Matlab then you need to use the
write_float_binary() function provided in
gnuradio-core/src/utils/write_float_binary.m. There are other files in
there
in case you want a different format. You will need to modify the files a
bit
since they are written to work with Octave.

Another approach is to load the variables as vectors from a .mat files
using
the loadmat function provided in python’s scipy.io library and use a
vector
source. For this case your code will look something like. I have loaded
variables from .mat files (filter taps etc) previously, but never used
them
as sources so that part is something you will have test.

from gnuradio import gr
from scipy.io import loadmat

variablelist = loadmat(‘/path/matfile.mat’)
var1 = variablelist[‘var1name’].tolist()

Karthik