UNIT Iv
IoT COMMUNICATION AND
OPEN PLATFORMS
4.1, loT COMMUNICATION MODELS AND API
| 41.1. loT COMMUNICATION MODELS
. {iy Request-Response
s Request-Response communication is a model in which the client sends the
request to the server and the server responds to the request
+ The server after receiving the request, decides about how to respond,
fetches data, retrieves resource, prepares the response and then responds to
the request.
% This model is a stateless model and each request-response pair is
independent.
Client ‘Server
Request Receives request
Sends process request
request looks for info, [>> Resource
to Response prepares response
sever | [* sends response
to client
Fig. 4.1. Request- Response Model
(ii) Publish-subscribe
This communication model has Publisher, Broker, Consumer,
% Publisher — Source of data, It sends the data to the topies which are
managed by broker.
% Consumer — Subscribe to the topics which are managed by the broker.
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Consumer = 3
. Publish Subscribe Model
(iti) Push-pull
> Push pull is a communication model in which the data producers push the
data to queue and the consumers pull the data from the queue.
The consumers and producers
need not be aware of each other.
The queues here also acts asa bufler, when there is a mismatch between
the rate of pushing the data by producers and the rate of pulling the data by
consumers.
Publisher Siete
[-——~[consumer=1 ]
Sends
message
Message pushed Messago pulled
queue to queues from queuos
Consumer=2 |
Fig. 4.3, Push-Pull Modet
iv) Exclusive pair
Mt is a bidirectional, fully duplex communication model that uses a persistent
connection between the client and server. ‘The connection can be closed by client
only afier the request y
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tis a stateful communi
ion model and the server is aware of all the open
connection.
Request to setup connection
Response accepting the request
Message from client to server
-—______rrrre|
Message from server to client
el
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setup reques
rmication begins with a connection
The wehsocket ¢
ehds with connection close request
Afier the connection establishment, the data is sent in full duplex mode
4.2. loT COMMUNICATION PROTOCOLS
The major focus of IoT is the communication between the objects, 7),
communication protocol allows the objects to send and receive data over jh,
jable for fof, The commonly use
cribed in detail below.
network. There are various protocols
communication protocols offered by loT are de
4.2.1. BLUETOOTH
+ Bluctooth is a wireless technology standard IEEE 802.15 used fo,
exchanging data over short range communication.
*%+ It follows the star configuration, with a single primary device that contro};
several secondary devices.
Bluetooth protocol stack
APPLICATIONS OBEX
Tsc spp | |RF COMM
tr DATA
VOICE L2caP
Hel
LMP
BASE BAND
RADIO
Fig. 4.8. Bluetooth protocol stack
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(0 Radio layer: This layer is responsible for radio fr
quency communication
hetween devices
(i) Baseband layer: Performs data transfer and link management bets
devices
(i) Link manager protocol: Manages the link between devices
(iv) Logical link control and Adaption protocol (LZCAP): Provic
multiplexing-protocols for data
protocols.
packets and supports higher
(x) Service Discovery protocol (SDP): It enables devices to discover service
provided by other devices.
(1) Telephony control protocol (TCS): It handles telephony related control
signals for cordless telephones.
(vif) Object Exchange (OBEX): a set of protocols for exchanging object such
as veards, vealender etc.
Blutooth Low Energy (BLE)
+ Bluetooth Low Energy (BLE) is designed for low power consumption
which is also popularly known as Bluetooth 4.0.
++. BLE uses wireless personal area network technology and optimized for the
devices that require long battery life.
teed
Transfer Connection
Fig. 4.9. BLE
BLE operates in 2.4 GHz ISM band and data rate are high at | Mb/s.
BLE 1OT applications
@ Wearable devices
(i) Smart home devices
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42.2. TIGBEE
ZigBee is a wireless technology IBEE 802.15 4 standard that prov
ommunication. ZigBe
for short rani
of communication protocol
< networking d
Jium range wirel
used in low data rate short ton
& Thuses AES 128 encryption for protecting information on air transfer.
Router (ZR),
onsists of ZigBee coordinator (ZC).
& ZigBee system
device (ZED)
(ZC acts a central unit and is responsible for transfer of data.
(if) ZR allows the data to pass through them to and fro to other devices,
(if) ZED interfaces with end device like sensor and actuator.
2C, ZR, ZED may be connected in form of star, cluster tree, mesh.
ZigBee Architecture
ee
Application Layer
ee
Application Inerface Layer
eo
ZigBee
Security Layer
Network Layer
Medium Access Control Layer IEEE
802.15.4
Standard
Physical Layer
Fig. 4.10, ZigBee Architecture
“> Physical layer: It translates the data packets in the over the air bits for
transmission and vice versa during the reception,
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step 7: On the main taspi-config screen, select finish and rehey a.
The UART serial port is enabled now
programming for Serial Write
#/UST / bin / eny Python
import serial
ger = Serial » Serial (port = ‘/dew /-H1y so’,
baudrate = 9600,
parity
Stopbi
P-NONE;
serial - STOPBITS — ONE
bytesize ~ serial - E
timeout = 1)
counter = 0
while 1: §
Ser - write (‘write counter: % d\n’ % (counter)
time - sleep (1)
counter +=.1
‘The function write the text “write counter : n” to any device at receiving end.
Programming for Serial Read
After setting baudrate, parity, stopbit etc. similar to above, write following code to
perform serial read.
while 1:
X= ser readline ( )
print X
This function read a line until it hits a line that ends
be omitted. Once it reads the value is stores it into X variable.
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46.2. SM COMMUNICATION PROTOCOL
SP ie
| by many different
srocol used
Common communication ;
fer modules, anid 24 GHZ wing
example, SD contd madules, REID card. ren
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trollers,
tninsmitter/recei vers all use SPI to communic
One unique benefit of SPI is the fact that data ¢
ad in a continuous stream, y
interruption. Any number of hits can be sent ar received in 4 “ue * Wit,
ecific number of bits. St,
12C nnd VAR, data is vent in packets, limited to a specific ny : * Sang
acket, so the da
sop conditions define the beginning and end of each Pi dota
interrupted during transmission.
Devices communicating via SPI are in at
lave (usually a
the controlling device (usually a microcontroller), while the slave (usually a senso,
from the master. The simple,
naster-slave relationship. The master,
display, or memory. chip) takes instruction
single slave system, but one master oa,
configuration of SPI is a single master,
control more than one slave (more on this below).
Fig. 4.22, SPI configuration
MOSI (Master Output/Slave Input) — Line for the master to send data to the
slave.
MISO (Master Input/Slave Output) - Line for the slave to send data to the
master
SCLK (Clock) ~ Line for the clock signal.
SS/CS (Slave Select/Chip Select) — Line for the master to select which slave 0
send data to.
Wires Used | 4
Maximum Speed Up to 10 Mbps
Synchronous or Asynchronous? | Synchronous
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The clock signal synchronizes the output of data bits from the master to the
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4.4.1. VERSIONS OF RASPBERRY Pi a —
I 1 | Ethernet | WiFi
soc _|_RAM_| USB port) 1_WiFi_|
Versions
Raspberry Pi -1 RCM 512 MB ' -
| |__2n35__| Macc
Raspberry Pi - 2 BCM | 1GB
2836}
Raspberry Pi-3 | ~BCM | 1GB 4 10/100 | 802.11n_
{ 2837 Mbits/s _|
Raspberry Pi ~ 4 BCM 2/418 4 10/100 | 802.11n
271 GB Mbits/s |
| Raspherry Pi - zero | pcm | 512MB | 1 (Micro s | -
L 2835 USB) |
4.4.2, RASPBERRY Pi- 4
Raspberry Pi - 4 is a single board computer with a dual display. The CPU of this
device comes with powerful and efficient 1.5 GHz quad core processor.
specifications / Oo
(i) Comes with Broadcom BCM 277, Quad-core Cortex A-72 — 64-bit SOC
processor.
(ii) RAM comes with 2 GB/4 GB/8 GB SDRAM.
(iii) 2-lane MIPI ports for display and camera port.
(iv) 40 pin GPIO headers
(v) One 3.0 USB port, one 2.0 USB port, one USB-C port.
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Fig. 4.18. Block diagram
Processor — Raspberry Pi system on chip (SOC) is Broadcom BCM 2835.
This contains ARM11 processor which Supports floating point operation,
The software needs to be compiled for ARMV6 to be used with Raspberry
Pi, BCM 2835 has timers, interrupt controller, GPIO ports, USB, DMA
controller, SPI master and slave, PVM, UART ports,
+ Power supply: It has SV power supply provided through micro-USB
% Camera Module: There is a port for connecting the camera module. There
are two versions of camera module.
(i) Standard version designed to take pictures in normal light.
(ii) NOIR version designed to use it together with an infrared light source
to take pictures in the dark,
% SD card: MicroSD card of 8 or 16 GB is generally used with operating
system installed in it.
+ Display: Any DV/HDMI Monitor can work as a display for the Pi
‘HDMI: High-Definition Multimedia Interface supports high quality digi
video and audio through a single cable. These ports are employe
transmitting audio and video signal between devices,
supports 5.0
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GSM is commonly used for 1OT cellular communicats
consumption, GSM models are id
low complexity, with low energy
long
vel distance
applications that need to transmit real time data ove
GSM Technology Architecture
9$7 interface
Radio nit Abie interface interface a
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i ; MSC ' ISDN
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j i i [Network
[ws] + i, (OMe
Mobile ! Base ! + Operational support * Public Network
station station subsystem
Network swtiching
Fig. 4.17. GSM Architecture
The main elements of GSM architecture.is
(i) Mobile station (MS)
(ii) Base station subsystem (BSS)
(iff) Operational support subsystem (OSS)
(iv) Network and switching subsystem (NSS)
Mobile station ,
It is made up of two entities.
(a) Mobile equipment: It can be portable and uniquely identified by IMEI
number.
(4) Subscriber Identity Module (SIM); It is a smart card that contains IMSI
number, It allows user to send voice or data transmission to or from other
subscribers
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(a) Base Transceiver Station (RTS): BTS encodes multiplexes, modulates and
the RF signal. 1 has transceiver unit
Rase station controller (BSC): BSC has multiple BTS arid manages
resources for BTS. It can handle transcoding and adaptation functionality
handover for cach MS power control
© operational support subsystem (Oss)
F
' Ji supports the maintenance and operation of GSM. OMC operation maintenance
centres used to monitor the performance of cach components. It has three functions:
(a) Maintain all telecommunication hardware and network operations.
(b) Manage all billing process
(c) Manage all mobile equipment
Network Switching subsystem (NSS)
lt is core network of GSM. It manages the switching functions of the system and
allows MSC to communicate with other networks.
k
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F
(a) MSC — Mobile switching center. It is associated with communication
switching functions.
(6) VLR — Visitor Location Register contains the exact location of all
subscribers present in the service area of MSC.
(c) HLR ~ Home Location Register contains pertinent data regarding
subscribers authorized to use GSM network.
(d) AUC — Authentication Center authenticates the mobile subscribers who
‘want to connect in network.
(¢) EIR - Equipment Identity Register keeps record of all allowed or banned
in the network.
(f) PSTN - Public Switched Telephone Network connects with MSC.
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4.3. OPEN PLATFORM
4.3.1, RASPBERRY Pi
The Raspberry Pi is a low cost, small sized computer that can be pl
into computer or TV Monitor.
Raspberry Pi runs over a Debian Linux platform called Raspbian which,
can perform like a normal desktop.
It offers a powerful environment to install variety of packages including
LAMP stack, python, Java and many more.
It allows interfacing sensors and actuators through general purpose 1/9
pins,
4.3.2. RASPBERRY Pi FORMATS
It comes in three different formats.
% Model B — It is the ‘full size’ board which contains Ethernet and USB
ports,
“ Model A - Lighter version of Raspberry Pi with lower specification with
no Ethernet port.
% Zero — The smallest Raspberry Pi kit with less computation, no USB and
no Ethernet.
4.4, RASPBERRY Pi - ARCHITECTURE
Raspberry Pi is single Board computer feature a Broadcom system on a chip
(SOC) with an integrated ARM — compatible central processing unit (CPU) and on-
chip graphical processing unit (GPU).
Most of the Raspberry Pi CPU is based on ARMI] or ARM Cortex processor.
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