MULTIFUNCTION SYSTEM BASED ON A STATE-OF-THE-ART

MICROCONTROLLER

José Manuel Rodríguez Ascariz, Luciano Boquete

Electronics Department, Alcalá University, Plaza S. Diego, Alcalá de Henares, Spain

Keywords: e-Payment, Point of Sale Terminal, Linux, Hardware Design, Ethernet, e-Health.

Abstract: This paper presents the hardware and software design of a new point of sale terminal. It is a multifunction

system with a wide range of functionalities: state-of-the-art user interface, a host of communication

possibilities (RS232, Ethernet, GSM, RTB MODEM) etc. The core of the whole development is the IMX21

microcontroller which allows the system design to be simplified. The Linux operating system is used due to

the complexity of the hardware systems and the fact that it has to be reconfigured for different

functionalities. The peripheral drivers have therefore been programmed. The result is a totally portable, low-

consumption system capable of performing many functions.

1 INTRODUCTION

This paper describes the hardware and software

design of a new portable terminal, the main purpose

of which is to serve as a Point of Sale Terminal

(POS), implemented with the state-of-the-art

technologies currently available. Devices of this type

are used on an increasingly massive scale every day

(e-Payment) in shops, the service sector, etc. One of

the most important functions of a POS is that of

connecting up to a financial institution and reading

the various types of payment cards (magnetic,

contactless, etc.), obtaining in each case an approval

code after remote consultation with the financial

institution and printing the corresponding receipt.

This function calls for a series of security standards

to be met, to cut down the chances of fraud and

mistakes (Dhem & Feyt, 2001). The options for

establishing this long-distance communication are a

conventional telephone line (IDSN), the mobile

telephony network (GSM) or the Ethernet protocol,

calling for specific modems to be designed for each

type of communication.

But these terminals can also be set up for other

functions, such as issuing car park tickets, issuing

fines, receiving orders in a restaurant, etc., and in

general, tasks involving the issuing of a paper ticket

and, in certain cases, connection with a central

control unit.

This device needs to be portable and user

friendly. The user interface has to have a keyboard

(normally reduced in size), a printer and a display

monitor (if possible in colour); if a touch screen is

used the information can be input from the screen,

thus making it even easier to use. It is also useful for

certain applications to have a multimedia sound

generation capacity, one use of which might then be

the giving of guidance in how to use the device.

Other worthwhile functions are those of

communicating with other electronic equipment

through USB, RS232, JTAG, for such tasks as

transferring information, reconfiguration, etc.

As regards the developers that might be used for

programming new system functions, the POS control

software needs to be easily programmable, cutting

down the design costs without forfeiting any of the

design reliability commitments. To this end a Linux

operating system has been implemented as the

control core of the hardware system and the

developer is furnished with a series of drivers to

harness the hardware resources to the full. This

allows the POS to be configured for new

applications, such as a variation of the information

shown on the display or the information furnished

by the printer, use of a given MODEM type, storage

132

Manuel Rodríguez Ascariz J. and Boquete L. (2006).

MULTIFUNCTION SYSTEM BASED ON A STATE-OF-THE-ART MICROCONTROLLER.

In Proceedings of WEBIST 2006 - Second International Conference on Web Information Systems and Technologies - Society, e-Business and

e-Government / e-Learning, pages 132-135

DOI: 10.5220/0001246901320135

 SciTePress

of certain types of events, use of different types of

cards, etc.

In light of all the above the general specifications

of the system developed are the following:

• 32-bit architecture with sufficient memory

for different complex applications and for storing

data.

• Flash memory, RAM and MMC and SD

CARD.

• User interface: keyboard, touch screen

(TFT) and thermal printer.

• Means of payment: readers for magnetic

cards, SAM and contactless cards (MIFARE).

• Communications: RS232, Ethernet, USB-

OTG, RTB Modem and GSM Modem.

• Low consumption, fed by rechargeable

batteries.

• Laptop, implying an integrated architecture

giving a compact and robust footprint, necessary due

to the terminal use conditions.

The main software specifications are an open

operating system with free 32-bit Linux code and the

development of the necessary APIs for controlling

all peripherals and programming particular

applications without needing to have an in-depth

knowledge of the hardware controlled.

The system is used for making money transfers

and as such has to meet the additional security

requisites to suit this circumstance: a) Security, the

terminal cannot be allowed to degrade the security

level of the cards themselves. b) If the terminal is

opened or dismantled, the sensitive information has

to be erased before allowing access. c) Its protection

systems include multiple-tamper-detectors to protect

customers' PINs, magnetic stripe data, application

programme and transaction data.

This paper has been broken down into the

following sections: after this introduction section

two below gives an account of the hardware block

diagram, with a comment on all the modules making

up the design; section 3 deals with the software

architecture; section 4 comments on the results and

winds up the article with the main conclusions.

2 HARDWARE ARCHITECTURE

Figure 1 shows the block diagram of the

implemented hardware system. This block diagram

gives a good idea of the device’s functionality; it

should also be taken into account that the system is

totally reconfigurable at hardware level: for example

the GSM modem could be implemented in a

commercial model instead of the RTB modem,

obviously accompanied by the suitable software.

The system has been designed around a state-of-

the-art microcontroller with a sufficiently wide

range of resources for the design to be optimised.

Freescale’s iMX21 (Freescale Semiconductor, 2004)

microcontroller is the central unit of the POS. This is

a device especially designed for multimedia

applications, with sufficient resources for

implementing the design: ARM9 core, JTAG

connection, timers, equipad, SLCD controller,

SDRAMC, MMC, multimedia accelerator, a

complete memory access interface, bootstrap, etc.

This microprocessor’s wealth of internal resources

has enabled the hardware development of this

system to be greatly simplified.

The following sections comment on the main

characteristics of each one of the blocks of figure 1.

CPU + Memory + Power: power feed control:

As already pointed out, the core of the system is the

IMX21. Its capacities have been optimised in the

interests of achieving the best possible design. This

circuit is fed with 3.2 volts, which is the working

voltage of most of the circuits. The module for the

control of the circuit power-feed is based on C.I.:

TPS 65012.

The system has been equipped with 32 Mb of

FLASH memory and 64 Mb of SDRAM (133 MHz),

sufficient for running the Linux Kernel and

implementing the applications for which the system

has been designed. The FLASH memory is

implemented with the low-consumption integrated

circuit S29GL128M, at 3.0 V

. The SDRAM is

Figure 1: Hardware block diagram.

CPU

RAM

FLASH

MMC

RS232

ETHERNET USB JTAG

MODEM

RTB

/GSM

KEYBOARD

TFT

PRINTER

AUDIO

ISO7811

ISO7816

ISO14443

POWER

CODEC

CPU

RAM

FLASH

MMC

RS232

ETHERNET USB JTAG

MODEM

RTB

/GSM

KEYBOARD

TFT

PRINTER

AUDIO

ISO7811

ISO7816

ISO14443

POWER

CODEC

MULTIFUNCTION SYSTEM BASED ON A STATE-OF-THE-ART MICROCONTROLLER

133

implemented with the integrated circuit

K4M513233A.

MMC/SDCARD: The multimedia cards allow

the storage and conveyance of mass data using a

widely used standard. For this reason an SD card

reader/writer has been implemented.

Means of payment

The following means of payment have been

incorporated into the POS:

• Magnetic stripe cards, (ISO 7811): These

are the oldest type of card and have the lowest

storage capacity but they are used on a mass scale

due to their low cost. A system has been set up for

reading the tracks recorded on the magnetic stripes

of these cards.

• Contact smart card, (ISO 7816): The

connection is made when the reader contacts a small

gold-plated area on the front of the card. The

integrated circuit TDA8007BHL is used for reading

the cards, according to standard ISO 7816, allowing

the control of up to 3 SAM. It is a dual card interface

for dual smart card readers.

• Contactless cards, (ISO 14443). Contactless

or proximity smart cards communicate at RF (radio

frequency). The point-of-sale terminal can

communicate with contactless cards by means of the

MIFARE protocol. Philips Mifare is the standard for

contactless and dual interface smart card and reader

technology operating at 13.56Mhz, in accordance

with ISO 14443, allowing a transfer rate of 106

Kbs/s up to a distance of 10 cms. The advantages of

contactless cards are their ease of use, immunity to

dirt, grease, etc; they are also less vandalism prone

since the reader needs no slots.

Communications

One of the design priorities was to ensure that

the system had a great capacity of communicating

with other devices in different formats. The system

has therefore been fitted with 2 RS232, USB ports,

and JTAG.

The system as designed allows for

communication through 2 different mobile telephony

modems; firstly, through a GSM modem and

secondly through the conventional telephone line

(RTB Model). The system also offers the

possibility of communicating via a GSM modem, by

exchanging the appropriate commands with a

conventional modem. Other option is to use the

conventional telephonic line; this module has been

designed on the basis of integrated circuit IPS3333.

The Ethernet protocol is widely used for

transferring information between computers and

other devices; its popularity is largely to due to

internet, facilitating access to a wide range of

information points. The integrated circuit CS8900A

has been used for implementation of Ethernet

communications; this circuit includes one on-chip

RAM, 10Base-T transmit-and-receive filters, and a

direct ISA-Bus interface. The CS8900A´s analog

front end incorporates a Manchester

encoder/decoder, clock recovery circuit, 10BASE-T

transceiver, and complete Attachment Unit Interface

(Figure 2).

20 Mhz.

CS8900A

C

RJ45

10BASE-T

1:1

1:2 .5

TRANSFORMER

(1)

(2)

(3)

(6)

Keyboard + printer + display

The user interface is implemented by means of a

keyboard of 5x4 keys, a thermal printer and a state-

of-the-art TFT, making it possible for state-of-the-art

graphics to be displayed. A colour touch screen has

been implemented, using the integrated circuit

ADS7843 for obtaining the point selected by the

user. The print is a roll paper, usefulness in this type

of devices

CODEC

The system has been designed with a codec

(WM8731) with audio amplifier and loudspeaker

outlet to endow it multimedia possibilities, including

the generation of sounds and reproduction of MP3

files.

3 SOFTWARE ARCHITECTURE

The Linux operating system is used for managing

the resources of the designed system, for the

following reasons:

• It is a scalable operating system that can be

run in a great variety of hardware devices. This also

means that it can be customised to meet the needs of

each case or application.

Figure 2: Ethernet communications.

WEBIST 2006 - SOCIETY, E-BUSINESS AND E-GOVERNMENT

134

• It is an open, well documented operating

system with a network of experienced developers.

• The manufacturer itself provides drivers in

this operating system.

The operating system is divided into the

following layers:

• System boot.

• Kernel, version 2.4.20 for ARM processors.

• Root file system, based on JFFS2.

The Kernel is mainly responsible for the

following functions:

• The scheduling of tasks

• The on-demand granting of non volatile

memory pages and volatile zones pages

• The inter-task communication

• The access control to non volatile memory

• The context switching

The dedicated operating system offers the

appropriate services for managing the system

hardware resources: display, printer, smart power

supply, etc.

4 RESULTS

Once the system had been implemented both at

hardware level (Figures 3 and 4) and at software

level, the relevant checks were carried out to make

sure the design specifications had been met. By way

of example, the consumption of the circuit on stand-

by is 50 microamperes; when running with the

colour display it is 300 milliamperes).

In short, the system as developed can be used as

an indispensable item in many services of e-

Payment, e-Commerce, e-Health (Hall et al.,

2003)(Song et al., 2002), etc.

ACKNOWLEDGEMENTS

This work has been supported by Ministerio de

Educación y Ciencia (Spain), ref: TRA2005-08734-

C02-01 and INTELLIGENT DATA.

REFERENCES

Dhem, J-F., Feyt, N., (2001). Hardware and Software

Symbiosis Helps Smart Card Evolution. IEEE Micro,

21, 14-25.

Hall, E. S., Vawdrey, K., Knutson, C. D., Archibald, J. K.,

(2003). Enabling Remote Access to Personal

Electronic Medical Records [Electronic version]. IEEE

Engineering in Medicine and Biology Magazine, 22,

133-139.

i.MX21.Applications Processor Reference Manual.

Freescale Semiconductor. 2004

Song, W. J., Ahn, B. H., Kim, W. H., (2002). Healthcare

Information Systems Using Digital Signature and

Synchronized Smart Cards via the Internet. In

ITCC´02 International Conference on Information

Technology: Coding and Computing.

Figure 4: Real system.

Figure 3: Real system.

MULTIFUNCTION SYSTEM BASED ON A STATE-OF-THE-ART MICROCONTROLLER

135