This document describes a project to develop a voice communication system over Wi-Fi networks using Raspberry Pi. The objectives were to create a Python application for full duplex voice calls between devices on the same Wi-Fi and build a mobile terminal with an LCD display and keypad. The system samples voice input, transmits over Wi-Fi, and supports future extensions. It was implemented using Raspberry Pi for processing and a Wi-Fi dongle for network access.

1. SUBMITTED BY
ARJUN S KUMAR
ARUN JOE JOSEPH
DEEPA RAMACHANDRAN
DON PAUL P
ROSHNI S A

2. INTRODUCTION
 Call costs that are generated for voice
calls within an institution could turn out
to be a handful if not managed properly.
 This project aims to develop a system
which can be used for voice
communication over a Wi-Fi network
provided within an institution.
 It would help to nullify the costs for voice
communication within an institution

3. OBJECTIVE
 To develop an application based on Python to enable
voice communication between devices that are
connected to the same Wi-Fi network.
 To assemble a mobile terminal with following features:
 Full Duplex communication over Wi-Fi.
 User interface with an LCD display and Keypad input.
 To support future extension of this system to
accommodate new devices.

4. BLOCK DIAGRAM

5. INTERFACING DIAGRAM

6. DESCRIPTION
 Voice input is given to raspberry pi via
microphone connected to the audio
input of sound card.
 Raspberry pi is used to process and
transmit voice signals.
 Wi fi dongle provides Wi-fi access to
raspberry pi.
 Voice signal is sampled and transmitted
via Wi-fi.

7.  LCD and keypad constitute user
interface part.
 LCD displays the welcome message
and messages indicating call initiation
and termination.
 In order to connect to a device, its IP
address must be entered. This is done
using interfaced keypad.
 The LCD also displays the IP address
and port number of the destination.

9. RASPBERRY PI

10. SPECIFICATIONS OF RASPBERRY
PI (MODEL B)
 ARM1176JZF-S700 MHz processor
 VideoCore IV GPU
 RAM-512 MB
 No built-in hard disk or solid-state drive
 Uses an SD card for booting and long-
term storage.
 2 USB ports
 10/100 Ethernet controller

11.  Linux kernel - based operating systems
 Raspbian is a Debian - based free
operating system optimized for the
Raspberry Pi hardware.

12. SPECIFICATIONS IN BRIEF

13. Wi-Fi
 Wi-Fi is a popular technology that allows
an electronic device to exchange data or
connect to the internet wirelessly using
radio waves.
 Spaces where cables cannot be run,
such as outdoor areas and historical
buildings, can host wireless LANs.
 An economical networking option.

14. LCD

15.  LCDs are economical, easily programmable,
have no limitation and can display special
and even custom characters (unlike seven
segment display).
 A 16x2 LCD means it can display 16
characters per line and there are 2 such
lines.
 In this LCD each character is displayed in
5x7 pixel matrix.

16.  This LCD has two registers, namely,
Command and Data.
 Command-stores instructions.
 Data-stores ASCII value of character to
be displayed.

17. KEYPAD

18.  Basic 16 button keypad.
 16 buttons of this keypad are arranged
in a 4x4 grid.
 The keys are connected into a matrix,
so, we only need 8 output pins (4-
columns and 4-rows) to scan through
the pad.
 An 8-pin extra-long header strip is
provided so that it can be plugged in to
the desired GPIO pins.

20. SERVER SIDE

21. SERVER SIDE
CHUNK = 1024
FORMAT = pyaudio.paInt16
CHANNELS = 1
RATE = 44100
RECORD_SECONDS = 10
WIDTH = 2
frames = []
HOST = '' # Symbolic name meaning
all available interfaces
PORT = 50010 # Arbitrary non-privileged
port

22. p = pyaudio.PyAudio()
stream =
p.open(format=p.get_format_from_width(WID
TH),
channels=CHANNELS,
rate=RATE,
output=True,
frames_per_buffer=CHUNK)

23. s = socket.socket(socket.AF_INET,
socket.SOCK_STREAM)
s.bind((HOST, PORT))
s.listen(1)
conn, addr = s.accept()
print 'Connected by', addr
data = conn.recv(1024)

24. CLIENT SIDE

25. CLIENT SIDE
import socket
import pyaudio
import wave
import time
#record
CHUNK = 16384
FORMAT = pyaudio.paInt16
CHANNELS = 1
RATE = 22050
RECORD_SECONDS = 60
HOST = raw_input("enter IP") # The remote host
PORT = input("enter port") # The same port as used by the server
num=1
while num==1:

26. s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect((HOST, PORT))
p = pyaudio.PyAudio()
stream = p.open(format=FORMAT,
channels=CHANNELS,
rate=RATE,
input=True,
frames_per_buffer=CHUNK)
print("*recording")
frames = []
for i in range(0, int(RATE/CHUNK*RECORD_SECONDS)):
data = stream.read(CHUNK)
frames.append(data)
s.sendall(data)

27. print("*done recording")
stream.stop_stream()
stream.close()
p.terminate()
s.close()
PORT=PORT+2
print("*closed")
num1=raw_input('press 1 to continue')
print('exit')

28. PROJECT SUMMARY
The objective was to develop
1) full duplex communication system
2) A user interface for interacting
We have successfully implemented both of
our objectives.

29. Why Python?
 Python is easy to write when compared
to JAVA.
 It is Dynamically typed language , so
that program length reduces.
 It has good compatibility with Raspberry
Pi.

30. Why Raspberry Pi?
 It is the cheapest available hardware
unit that satisfied our requirements.
 It has GPIO pins tat enabled to interface
with external hardware.
 It has a huge online support.

31. THE FEATURES OF FINAL END
PRODUCT
 The device we developed is of compact
size and works stand alone.
 It has at present a range of about 10m
circular radius from base station.
 It offers reconnecting and retry features
 It can be configured for any Wi-fi
network.

32. OTHER APPLICATIONS OF
PROJECT
 Can be used at disaster management
locations as the last resort of medium
range communication.
 Can be used as a broadcast device for
wireless audio speakers.

33. FUTURE DEVELOPMENTS
 Range can be extended by using a more
powerful router.
 When going for mass production the
cost can again be reduced.
 Can add texting features as well.