Design of Smart Sensor Interface for Industrial WSN

in IoT Environment using Standard of IEEE1451.2

(STIM)

Nilima Khirdekar Aparna Shinde

Department of E&TC Department of E&TC

D. Y. Patil College of Engineering, Akurdi, Pune. D. Y. Patil College of Engineering Akurdi, Pune.

nilimakhirdekar@gmail.com asshinde1@rediffmail.com.

Abstract— To monitor applications in any environment, data

related to that particular application is required. For this

purpose, a sensor interface device is necessary which is used for

sensor data collection of industrial wireless sensor networks in

IoT environment. However, the general identification

information of sensors is restricted by the device. In the Internet

of Things (IoT) environment, for collecting the information of

sensors, each sensor connected to the device has to write a

program code in software language which is very complicated

and time consuming. To solve this problem, this paper presents a

new method to design a Smart Sensor Interface device in which

FPGA is used as core controller for reading data in parallel and

in actual time (in which data collecting process occurs) with high

speed on multiple different sensors. The standard of IEEE 1451.2

intelligent sensor interface specification is also used in this design,

which introduces Transducer to Microprocessor communication

protocols & TEDS formats for sensor information. A new

solution is provided for the traditional sensor data accessions

system by combining the FPGA programmable technology with

the standard of IEEE1451.2 intelligent sensor specification.

Keywords— FPGA, IEEE1451 protocol, TEDS, Internet

of Things (IoT), Sensor data acquisition.

I. INTRODUCTION

Wireless Sensor Network (WSN) is a wireless network

consisting of spatially distributed autonomous devices using

sensors that are used to physical or environmental conditions

such as temperature, pressure sound, intensity etc and to

cooperatively pass their information through the network to

the main location. Therefore, WSN have been employed to

collect data about physical circumstances in various

applications such as surveillance, ocean monitoring, and

habitat monitoring [2]-[5]. As growing technologies brought

about rapid approaches in modern wireless

telecommunication, Internet of Things (IoT) is also popular

now a days and is expected to bring many advantages to

numerous application areas including industrial WSN systems,

and healthcare systems manufacturing [11].WSN systems are

well-suited for long-term industrial environmental data

accession for IoT presentation[6]. Sensor interface device is

essential for detecting various kinds of sensor information of

industrial WSN in IoT environments. It is very useful for

acquiring sensor data. Thus, we can better understand the

surrounding environment information. However, in order to

get the requirements of long-term industrial environmental

information collection in the IoT, the sensor interface device

can accumulate multiple sensor data at the same time, so that

more accurate and various kind of data information can be

collected from industrial WSN. With fast development of IoT,

major manufacturers are working on the research of sensor

acquisition interface equipment which supports multiple and

different kinds of sensors [24]. There are a lot of data

acquisitions multiple interface equipments with growing

technologies on the market. But these interface devices has a

particular working style, so they are not individually

compliant to the changing IoT environment. Meanwhile, these

data acquisition interfaces has some boundary limits in

physical properties of sensors. Now, micro control unit

(MCU) is used as the core controller in normal data

acquisition interface device. Micro control unit has the

advantage of low cost and low power consumption, which

makes it comparatively easy to implement. But, it performs a

task by way of interrupt, which makes these sensor acquisition

interfaces not actually parallel in collecting various &

different sensor data. On the other hand, FPGA has unique

hardware control logic, synchronicity & real-time performance

[12],[13] which enable it to achieve parallel acquisition of

various sensor data and greatly improve real-time performance

of the system Also FPGA architectures make the more

flexible, therefore the interface device which include FPGA as

controller is more flexible to IoT environment. However, in

IoT environment, different industrial WSNs involve a lot of

complex and various types of sensors. At the same time, each

sensor has its own requirements for data collection & readout

and also different users have their own applications that

require different types of sensors. It leads to the necessity of

writing complex sensor driver code and data collection

procedures for every sensor that are (mostly first time)

connected to interface device, which brings many challenges

to the researches.

The remainder of this brief is organized as follows. Section

II provides a background work of data acquisition device.

Section III presents the introduction to IoT. Sections IV

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presents introduction to STIM. Section V presents

Architecture of sensor interface device. Section VI provides

Implementation part of this project. Section VII gives

Simulation results and section VIII gives the Conclusion of

this paper work.

II. BACKGROUND WORK

Sensor data acquisition interface device is the main part of

study on industrial WSN application. In order to

systematize a wide range of intelligent sensor interfaces in the

market that is information of multiple sensors should be

collected intelligently and to solve the compatibility problem

of advanced sensors, the IEEE Electronic Engineering

Association has launched IEEE1451 smart transducer

interface module standard protocol suite for the future

development of sensors. The protocol demands a series of

specifications from sensor interface definition to the data

accession. The STIM interface standard IEEE1451 enables

sensors to irresistibly search network. But, the sensors with the

protocol standard have a high cost and are not that much

flexible in industrial WSN in IoT environment. At the present,

examples of intelligent sensors available on the market and

adaptable to this standard have some boundary limits. It is

obvious that such restriction should be released, and a

reconfigurable various sensor data acquisition interface with

good compatibility and normative interface standard needs to

be developed in IoT environment. To get the solution for these

problems, some dedicated hardware interfaces based on the

IEEE1451 have been recently proposed, and they are capable

of interfacing with different sensor typologies.

By observing the above issues, this paper designs and

realizes a smart sensor interface for industrial WSN in IoT

environment. This design presents many advantages as

described below. First of all, FPGA is used as the core

controller to release the restriction on the universal data

acquisition interface, and realize truly parallel acquisition of

sensor data. It has not only improved the sensor data collection

efficiency of industrial WSN, but it also allowed a wide range

of applications for the data acquisition interface device in IoT

environment. Secondly, a new design method is proposed in

this paper for different kinds of sensor data collection interface

that can accomplish plug and play for various types of sensors

in IoT environment. The design system uses the IEEE1451

interface protocol standard that is used for smart sensors of

automatically searching network. For the sensors not based on

IEEE1415 protocol standard, the data accession interface

system can achieve the function of plug and play.

III. INTERNET OF THINGS (IOT)

Imagine a world where billions of objects can recognize,

communicate and share information, all interconnected over

public or private Internet Protocol (IP) networks. These

interconnected objects/ things have information regularly &

daily accumulated, analyzed and used for processing,

providing a wealth of intelligence for planning, management

and decision making. This is the world of the Internet of

Things (IoT). The IoT concept was invented by a member of

the Radio Frequency Identification (RFID) development

community in 1999, and it has recently become more relevant

to the practical world largely because of the growth of mobile

devices, embedded and ubiquitous communication, cloud

computing and data analytics.

The Internet of Things (IoT) is the network of physical

objects such as devices, vehicles, buildings and other items

even persons also embedded with electronics,

software, sensors, and network connectivity that enables these

objects to collect and exchange data. The IoT allows objects to

be recognized and controlled remotely across existing network

infrastructure, creating opportunities for more direct

integration of the physical world into computer-based systems,

and resulting in improved efficiency, accuracy and economic

advantage; when IoT is augmented with sensors and actuators,

the technology becomes an instance of the more general class

of cyber-physical systems, which also encompasses

technologies such as smart grids, smart homes, intelligent

transportation and smart cities. Each thing is uniquely

identifiable through its embedded computing system but is

able to interoperate within the existing Internet infrastructure.

fig. (1). Layers present in IoT system.

In IoT there are seven layers present as shown in fig. (1) for

collecting and interchanging the data in IoT environment.

“IoT” is all about physical items communicating with each

other, where machine-to-machine (M2M) communications

and person-to-computer communications will be extended to

“things”. Since IoT is associated with a large number of

wireless sensor devices, it generates a large number of useful

information.

fig. (2) IoT architecture.

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The main three layers of the architecture of IoT that are

required in this paper work are shown in fig. (2) and that are:

1) perception layer; 2) network layer; and 3) application layer

[19]. The design of data acquisition interface is mainly carried

out at the perception layer of IoT [20]. The perception layer of

IoT is mainly composed of sensors, Zigbee network, RFID

readers, cameras, M2P terminals, M2M terminals, and various

data collection terminals. In perception layer and Network

layer the information related to sensor devices in any

applications is get collected. Therefore this paper focuses on

these two layers of IoT architecture.

IV. SMART TRANSDUCER INTERFACE MODULE

Sensor is the general term of the information acquisition

devices, and often used to convert various measurements into

electrical signals, it is an important part to acquire input

signals for kinds of monitoring technology system. As the

development of communication technology, computer

technology, semiconductor technology and network

technology, the sensor technology is walking to the direction

of becoming more networked and smart which making a

continuous improvement of networked monitoring technology.

Compared with the conventional sensor, smart sensor not only

has the function of information collection, but also has a

certain ability of self checking, self analyzing, judgment and

two-way communication [21]. The protocol Conversion is

often required when we connect sensors to the network. In

order to solve this problem, we need a common sensor

interface protocol.

IEEE1451 is an open standard of smart sensor interface

protocol suit, used for unified the interface protocols between

sensors and different network. The American national

standards institute of technology and IEEE association of

sensing technical committee jointly organized to formulate a

common smart sensor communication interface protocol and

related standards. Among IEEE1451 protocol suit, the

IEEE1451.2 is more often used. The IEEE 1451.2 standard

introduces the concept of the STIM [23]. A STIM can range in

complexity from a single sensor or actuator, to many channels

(up to 255 channels) of transducers (sensors or actuators). A

transducer channel is referred as "smart" in this paper, because

of the following three features:

• It is described by a machine-readable Transducer Electronic

Data Sheet (TEDS).

• The control and data associated with the channel are digital.

• Triggering, status, and control are provided to support the

proper functioning of the channel.

Fig. (3). STIM overall design structure diagram.

The overall design structure diagram of STIM is shown in

fig. (3). A STIM contains the following four functions:

1) Transducer Electronic Data Sheet,

2) The Data Transmission module,

3) Channel Trigger Module,

4) Registers Management Module.

TEDS is the logic to implement the transducer interface,

TEDS memory requirements are typically less than two

kilobytes. A STIM is controlled by a NCAP module by means

of a dedicated digital interface [23]. This interface is not a

network. The NCAP mediates between the STIM and a digital

network, and may provide local intelligence. It is desirable

that the STIM and NCAP add little size or cost to the

transducer(s) they describe and interface. Sensor independent

interface TII is the communication part of the smart

transmitter module and network capable application processor

(NCAP).

V. ARCHITECTURE

This paper designs a smart sensor interface device that

integrates data collection, data processing, and wired or

wireless transmission together. This equipment can be used in

different application areas of the IoT and WSN to collect

various types of sensor data in real time. This paper programs

the STIM module of IEEE1451.2 corresponding protocol in its

FPGA. Therefore, our interface device can automatically

discover sensors connected to it, and to collect multiple sets of

sensor data in parallel manner with high-speed. FPGA is core

controller of the interface device. It is used to control data

accession, processing, and transmission intelligently, and

make some preprocessing work for the collected data. The

driver of chips on the interface device is also programmed

inside the FPGA.

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Fig. (4). application and working diagram of the smart sensor

interface device.

In terms of data transmission, the design can achieve wired

communication through Universal Serial Bus (USB) interface

and wireless communication through Zigbee module.

Therefore, we can choose different transmission mode of the

device in different industrial application environments. Fig. 4

is the application and working diagram of the smart sensor

interface device. In practice, the designed device collects

analog signal transmitted from colour sensors, light intensity

sensors, and other similar sensors through an analog signal

interface. It can also collect digital signal transmitted from the

digital sensors, such as temperature sensors, digital humidity

sensors, and so on, through a digital signal interface. The

analog to digital Converter module and signal interface on the

interface device are controlled by the FPGA. The core

controller i.e. FPGA sets the collected data into Random

Access Memory (RAM) on the interface device and these

collected data can be transmitted to the host computer side by

way of USB serial wired communication or Zigbee wireless

communication, so that the user can analyze and process the

collected information.

VI. IMPLEMENTATION

1) Hardware Architecture:

The FPGA hardware block diagram of Smart Sensor

Interface device is shown in fig. 5. The overall structure of

smart sensor interface consists of FPGA chip (Spartan-6) ,

high-speed RAM, power supply, communication circuit for

turning USB to serial port, Zigbee wireless communication

module, digital sensor interface for digital sensors, analog

sensor interface for analog sensors and I2C protocol

interface for the sensors that fall into category of I2C

communication protocol.

Fig. (5). FPGA Hardware block diagram of Smart Sensor Interface Device.

The hardware system can also send and receive data

besides the basic sensor data acquisition. It can send data to

the control centre via USB serial port or Zigbee wireless

module. Zigbee wireless communication module can be used

as wireless data transceiver node when the main controller

receives trial or executive instructions.

2) Verilog design:

The overall structure diagram of Verilog part of the system

is shown in fig. 6.

Fig. (6). Overall structure diagram of verilog part of the system.

1) Part 1: As per the structure diagram of STIM module,

this paper designs Digital sensor interface, analog sensor

interface and I2C bus interface i.e. in this paper, by

using these 3 sensor interfaces a transducer electronic

datasheet is designed for digital sensors, analog sensors

and for the sensors which uses I2C bus protocol for

transmitting and receiving data. For the designing of

TEDS of Analog sensors and sensors based on I2C

protocol, this paper uses the datasheet of 8-Bit

microprocessor Compatible A/D Converters with 8-

channel multiplexer and 8-bit CMOS data acquisition

device with a serial I2C bus interface respectively.

2) Part2: In this part this paper implements, Master state

machine which manages the switching process between

each STIM state, include data transmission, triggering

the sensor channel and control of data storage etc as

shown in fig. 7.

Fig. (7). STIM State Machine design structure diagram.

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According to related characteristics of IEEE 1451.2

protocol, the master state machine switches operations

of the process as shown in fig.8.

Fig. (8). STIM main state machine process diagram.

3) Part 3: In part 3, the paper implements the verilog code

for serial port communication module. In this part, the

standard of serial communication RS-232 is used for

data transmission. The code of serial communication

standard is programmed by using baud rate (speed of

data transmission) of 9,600 bits per seconds.

4) Part 4: In this part, single port high-speed RAM is going

to code in verilog software for storing the collected data

of sensors.

VII. SIMULATION RESULT

The Results of the simulation for collecting the data from

different sensors is given in the following figure for 3 types of

different sensors.

For digital Sensors:

For Active High digital sensor, when input to the

sensor is High then output we get that should be High

& if input is low then output is also low. But this is

reverse in case of Active Low digital sensor. The

simulation results for both Active low and Active

High Digital Sensors is shown in following figure

(9a) and (9b) respectively.

Fig. (9a). Simulation result for Active Low

digital sensor with “a” as I/p and “d” as o/p.

Fig. (9b). Simulation result for Active High digital

sensor with “a” as I/p and “d” as o/p.

1) For Sensors based on I2c protocol:

For this type of sensors the output of simulation

proposed methodology got as per serial data

line (SDA) and serial clock line (SCL) is as

shown in following fig. (10).

Fig (10). i2c bus serial communications.

2) For Analog Sensors:

For analog sensors, the proposed methodology got

the output results which are shown fig (11).

fig. (11). Simulation result for ADC.

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The simulation result for serial Communication rs232 is

shown in fig. (12).

fig. (12). Simulation result for rs232.

VIII. CONCLUSION

This paper describes a smart sensor interface for

industrial WSN in IoT environment. The system can

collect identification information of sensor intelligently. Its

design is based on IEEE1451.2 protocol by combining

with FPGA and the application of wireless communication.

It is very suitable for real-time performance and effective

requirements of the high-speed data acquisition system in

IoT environment. The application of FPGA simplifies the

design of peripheral circuit and it also provides parallel

processing of data collection. FPGA also makes the whole

system more flexible and it expand the range of

applications in IoT for the sensor interface device.

Application of IEEE145.2 protocol enables the system to

collect sensor data intelligently. By using this device,

information of different types of sensors (that falls into

above described three categories) can be connected to the

system without writing any complicated program.

20% working of this project is remaining and it is on the

way of completion. Main design method of the smart

sensor interface device is described in this paper.

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