Past paper GCSE Unit 01 English Lit Exploring Modern Texts - AQA

20 Pages·2013·0.16 MB·English

GNUradio Python
Programming
KC Huang
WINLAB
Outlines
Python Introduction
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Understanding & Using GNU Radio
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What is GNU Radio architecture?
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How to program in GNUradio? (Python and
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C++)
An example: dial-tone
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Useful Resources
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Python - running
Why Python?
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Object-oriented
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Free
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Mixable (python/c++)
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Python scripts can be written in text files
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with the suffix .py
Example:
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$ python script.py
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This will simply execute the script and return to the
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terminal afterwards
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Python - format
Module: a python file containing definitions and
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statements
from pick_bitrate import pick_tx_bitrate
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(from file import function)
from gnuradio import gr, (or *)
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(from package import subpackage or all)
Some modules are built-in e.g. sys (import sys)
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Indentation: it is Python’s way of grouping
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statements
Example:
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while b < 10:
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print b
return
Body of loop has to be indented by the same amount
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to indicate statements of the loop
WINLAB
Python – function & class (1)
Function definitions have the following basic
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structure:
def func(args):
return values
Regardless of the arguments, (including the case of no
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arguments) a function call must end with parentheses
Example:
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def f1(x):
return x*(x-1)
f1(3) = 6
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Python – function & class (2)
Classes
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class ClassName:
<statement-1>
. . .
<statement-N>
Objects
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x = ClassName() creates a new instance of this class and
assigns the object to the variable x
Initial state: for instantiation and parameter pass
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def __init__(self):
<statement-1>
WINLAB
Python – function & class (3)
class cs_mac(object):
def __init__(self, tun_fd, verbose=False):
self.tun_fd = tun_fd
self.verbose = verbose
self.fg = None
def main_loop(self):
min_delay = 0.001 # seconds
while 1:
payload = os.read(self.tun_fd, 10*1024)
if not payload:
self.fg.send_pkt(eof=True)
break
if self.verbose:
print "Tx: len(payload) = %4d" % (len(payload),)
delay = min_delay
while self.fg.carrier_sensed():
sys.stderr.write('B')
time.sleep(delay)
if delay < 0.050:
delay = delay * 2 # exponential back-off
self.fg.send_pkt(payload)
WINLAB
GNUradio Architecture
Sender
User-defined
RF
USB FPGA DAC
Code
Front end
mother board
daughter board
PC
USRP
GNU radio has provided some useful APIs
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What we are interested in at this time is how to
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use the existing modules that has been provided
in GNU radio project to communicate between
two end systems
WINLAB
GNUradio Architecture - software
How these modules co-work?
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Signal processing block and flow-graph
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C++: Extensive library of signal processing blocks
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(cid:131) Performance-critical modules
Python: Environment for composing blocks
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(cid:131) Glue to connect modules
(cid:131) Non performance-critical modules
Signal Processing Block
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Source: No input
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noise_source, signal_source, usrp_source
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Sink: No outputs
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audio_alsa_sink,usrp_sink
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Processing blocks: one or more inputs/outputs
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GNUradio Architecture – software(2)
V2 V2
C++ C++
C++ C++ Sink
C++ C++
V1 V1
V3 V3
Source
At python level, what we need to do is always just
to draw a diagram showing the signal flow
from the source to the sink in our mind.
WINLAB