Sistema Duplex De Comunicación Inalámbrica De Audio

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The Eighth International Conference on Electronic Measurement and Instruments ICEMI2007

A Duplex Wireless Audio Communication System

Yun Ying Dai Shuguang Mu Pingan Su Tianfa

University of Shanghai for Science and Technology, Shanghai 200093 China

Abstract: This paper mainly introduced the principle,

hardware, software, functions and technical difficulties of the

system. This system applied wireless communication technique,

audio frequency technique and network technique. The

functions was carried out by embedded system. Its core part

was Micro-Controller Unit ET44M210, and it included several

Sub-systems. They were J2A Audio Encoding and Decoding

Sub-system, RF Wireless Communication Sub-system, OLED

Manifestation Sub-system, Alarm Sub-system and FLASH

Memory Sub-system. This system was used in the hospital and

it can make real-time communication, medical record

management, calling alarm and calling manifestation integrate

together then worked perfectly with each other. This duplex

wireless audio communication system contacted patient and

paramedic quickly and efficiently, so it can raise the nursing

efficiency, lighten the intensity of labour, improve the service

level of hospital.

Keywords: ET44M210, wireless communication, J2A, audio,

OLED, duplex

1 Introduction

With the rapid development of technology, the

wireless communication and the audio frequency

technique have been being extensively concerned by

the scientists all over the world. The wireless

communication technique can not only avoid network

breakdown by routing, but also have a beautiful

appearance. The audio frequency technique is the

predominant direction of intelligence calculator

research and the key technique of man-machine

communication. OLED manifestation technique will

have a bright future because of its special structure,

and its advantage can be seen obviously such as high

light rate and no angle etc.

The establishment of this system is according to

the hospital nursing requirement. its purpose is to

carry out the real-time communication between nurse

and patient. Currently, most local hospitals call

systems are still in the stage of bell calling, only a few

hospital carried out the function of electronic

conversation. In these hospitals, they only can realize

conversation but cant make electronic conversation,

patient's medical record management, alarm and

manifestation integrate together. Now this duplexwireless audio communication system carries out

those functions above.

2 System Principle

Design scheme of this system is to use high

capable MCU and peripheral modules. Seen from the

whole structure, the system can be divided into a

nurse station host and several patient extensions,

which are independent mutually. Seen from the

function, the system can be divided into MCU, RF

Wireless Communication Sub-system, J2A Audio

Encoding and Decoding Sub-system, OLED

Manifestation Sub-system, FLASH Memory

Sub-system, Alarm Sub-system and Keyboard. Every

Sub-system works together.

The core part of the system is MCU ET44M210,

and it can make all Sub-systems work in a moderate

situation. The Audio Sub-system adopts J2A Audio

Encoding and Decoding module ET83X432, carries

out the function of voice recording and broadcasting.

The RF Wireless Communication Sub-system adopts

wireless module RFW102. It can transfer audio data

or keyboard data quickly and accurately. The OLED

Manifestation Sub-system adopts ET52141, and can

show the extension number when extension is calling

or called. The Alarm Sub-system is used in the

emergency. The keyboard mainly completes number

calling and voice adjusting. And FLASH MemorySub-system saves bell ring.

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1-4244-1135-1/07/$25.00 2007 IEEE.


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This systems principle is shown in Figure.1.

From Figure.1, we can see the systems every part and

take the systems working principle.

Fig.1 principle chart of this system

The main functions of this duplex wireless audiocommunication system include:

1Nurse Station Host and Patient Extension can call

each other mutually.

2After calling connection, nurse and patient can

communicate with each other in duplex way.

3When host or extension is called, its bell will ring.

4From beginning to the end of the conversation, the

host will show the extension number on display

screen.

5In the nurse station, there will be a medical record

and three-color LEDs for each patient. When nurse

press the corresponding keystoke on the patient

extension, LEDs will show patients nursing state

(calling, nursing or emergency).

6Once the emergency appears, host and extension

will all sound alarm.

7All sorts of data is transferred by Wireless

Sub-system.

3 Hardware Design

3.1 ET44M210 MCU

ET44M210 is a 8-bit micro controller. High

operation speed, low price and high performance are

its remarkable characters. It has USB+BB sub-micro

controller and 8-bit simple instruction. Besides having

the function of micro controller, it also provides ten

peripheral IP modules, such as wireless transfer

module base band (BB). So application of theET44M210 has more flexibility on the design.

Through 42 I/O ports of the MCU, the peripheral

Sub-systems can be connected and controlled by

MCU.

3.2 RF Wireless Communication Sub-system

RF Sub-system applies RFW102, which is the production of RFWaves company. Its working

frequency is 2.4 GHz and its tallest transfer speed is

1MBPS. The RFW102 is very appropriate to this

system, because MCU has an IP module called BB

which has specifical interface to connect RFW102.

What's more, RFW102 matches the technical

specification of American federal correspondence

committee (FCC). RFW102 connects host and

extension to ensure the whole system working

together perfectly. It is the important module of thesystem and we can see the interface circuit diagram in

Figure.2.

Figure.2 the interface circuit diagram of ET44M210 and

RFW102

3.3 J2A Audio Encoding and Decoding

Sub-system

J2A Audio Encoding and Decoding Sub-system

makes use of ET83X432 module to carry out

functions such as recording, encoding, decoding and

broadcasting etc. It applies JPEG 2000 Audio

Technique which can compress voice into J2A form

and broadcast it directly, so it has the ability of

encoding and decoding high quality audio information.

This chip controlled by MCU supports simplex

operation mode and duplex operation mode.

ET44M210 and ET83X432 are all the production of

Etoms Electronics Corp, so they have proper interface.

They won't appear voltage and current mismatch.

ET83X432 carries out the duplex audio

communication between nurse and patient.3.4 OLED Manifestation Sub-system

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Manifestation Sub-system uses Organic Light

Emitting Diode (OLED). Its module number is

ET52141, which supports 96x96 dots and 65 colors.

Whats important is that it has convenient operation

ability and efficient data transfer ability. Its mainfunction is to display the number of extension, then

nurse can fix easily which extension is calling by

vision. According to the data transferred by RF

wireless module, the system host controls OLED.

3.5 Other Sub-systems

Alarm Sub-system is the assistant part of this

system, and has two functions to remind people. First,

it can remind nurse to know the emergency. Second, it

can remind patient of the operations regulation and

agenda. FLASH Memory Sub-system mainly savesthe bell ring. When host or extension is called, its bell

will ring. So it can remind nurse and patients to

answer the calling in time.

4 Software Design

Software program of the system uses the

assemble language of Etoms single chip. This kind of

language is simple, takes small space and carries out

all sorts of functions easily.

4.1 Realization of Wireless Communication

Protocol

(1) wireless transfer of key information

When host calls extension, the host sends 128

bytes extension numbers which is received by

extension. If the received number is same as its own

number, the extension will ring. If they are different,

the extension will not respond. When extension calls

host, extension sends 128 bytes extension numbers

which is received by host. the host judge whether it is

the extension number. If it is, the host will ring,

otherwise the host will not respond.

When conversation is over, any side (host or

extension) can put down the phone. The active side

should send hang up signal through wireless

Sub-system. As soon as another side receives the end

signal, the conversation will be ended immediately.

Key information transfer can make conversation begin

and over.(2) wireless transfer of audio information

After calling is connected, the wireless audio

conversation is established and the wireless module is

working in the stage of audio data transfer. Software

design applies the interruptions of MCU which are

TX_EMPTY, RX_OF, TX_FIFO_AE(almost empty)and RX_FIFO_AF(almost full). When searching the

interruption sign bit setted up, MCU will send data to

TX_FIFO or receive data from RX_FIFO. AA is the

synchronous head of the wireless communication data.

The wireless program flow chart is shown in Figure.3

and Figure.4.

Fig3 send flow chat Fig.4 receive flow chat

4.2 Software Realization of Duplex Wireless

Audio Communication

In the software design, the most important of the

Audio Sub-system is the realization of audio duplex

operation. Its working principle can be seen from

Figure.5.

Fig.5 duplex working principle of audio module

ET83X432 DATA FIFO can temporarily save 64

bytes data. When encoding, if Aux FIFO fills with 64bytes and can't read out immediately, ET83X432 will

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stop compression. When decoding, if Main FIFO is

empty, ET83X432 will stop work. So in the duplex

operation mode, we must ensure that two FIFOs are

neither empty nor full.

5 Technical Difficulty of System

There are several technical difficulties in this

system. And we have already hurdled them to realize

the functions. We can see the solutions as follows:

1The establishment of wireless communication

protocol. If we want to carry out real-time

communication, we must set up a proper protocol. We

establish a protocol that can send or receive 8 bytes

per time with high frequency.2The duplex communication. Because RWF102 is a

kind of half duplex working chip, how can we carry

out duplex working style? We write software to make

up defect of the hardware.

3The interception ability of wireless signal, how to

prevent interference. We choose RWF102, for it

adopts two kinds of techniques to acquire good

interception ability: First is a RSSI, the other is the

usage of an interception arithmetic.

4OLED must be illumed and refurbished in time.

This problem is solved by the software design.

6 Performance Analysis

This system has stable function and good

dependability. It uses 5V electrical source, so it is safe

and convenient. It avoids the disadvantages of wired

system such as troublesome routing, low utilization

rate and so on. Although the wireless call system

havn't wiring trouble, its transfer distance isn't very far.

The wireless medium isn't protected by environment

like wire medium, so it may be interrupted or decayed.

We should use proper methods to settle these

problems according to the actual application.

7 Summarize

This system makes use of wireless

communication technique, J2A audio Encoding andDecoding duplex communication technique, no angle

OLED manifestation technique and FLASH memory

technique. And it realizes the function of dupex

wirless audio communication and real-time

manifestation. This system's small structure, simple

communication protocol and convenient applicationare all its advantages. It can raise the nursing

efficiency, lighten the intensity of labour, improve the

service level of hospital greatly.

It is a duplex communication system that suits

for the low level market. It not only can be applied in

the hospital sickroom, but also can be used in some

small working places. To sum up, this system has high

practicability and plasticity. If we modify software of

the system, it can be used in other realms

conveniently.

References

[1]competition committee. Transactions of Shanghai embedded

system innovative design competition in 2005[M].Beijing:

Beihang University Press, 2005.10

[2]Zhu Renlong, Zhao Junyi, Huang Yong. ET44M210 SoC

micro controller based on IP design. Journal of Singlechip

and Embedded System Application, 2004.6, pp: 50-52

[3]Liu Mingfang, Xiang Xuejun. Design and Application of RF

Front End Using RFW102 Chipset, Journal of China Three

Gorges Univ. (Natural Sciences), Vol 27No 5,2005.10, pp:

434-436

[4]Shen Huaiyang, Song Jianbo, Wang Shijie. First Exploration

of Voice Technology Applied to Intelligent Instrument. New

Technique and New Instrument. Vol 21, No 4, 2004, pp:

21-25

[5]Fan Guanghua, Chen Huimin. Implementation of the Novel

IP Phone Terminal. Transactions of wireless science and

technology proseminar. Vol 8, No 10, 2002, pp: 303-306

Author Biography

Yun Ying female, born in Jan 1984, master. Study in

University of Shanghai for Science and Technology, Optical

and Electronic Engineering College, Measuring and Testing

Technologies and Instruments Department. Research directions

include image processing and detection technique etc.

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