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
Copyright
c
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
DC
. 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