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8/4/2019 Sistema Duplex De Comunicacin Inalmbrica De Audio
1/4
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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The Eighth International Conference on Electronic Measurement and Instruments ICEMI2007
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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The Eighth International Conference on Electronic Measurement and Instruments ICEMI2007
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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The Eighth International Conference on Electronic Measurement and Instruments ICEMI2007
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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