Design of wireless handheld magnetic stripe card information terminal

0 Introduction

A magnetic stripe card is an identification card made of magnetic material. Because magnetic stripe cards are easy to carry, low-priced, and easy to popularize, they have been widely used in bank cards, membership cards, medical treatment cards and other application fields. This paper designs a handheld wireless magnetic stripe card information terminal based on GPRS. After the handheld wireless magnetic stripe card information terminal reads the user identification on the magnetic stripe card through the magnetic stripe card interface, it sends the user identification information and operation information to the central server through the GPRS wireless network. After the central server performs corresponding processing, it returns the response information to the handheld information terminal for processing and display. The handheld wireless magnetic stripe card information terminal can work independently without relying on a PC, has low cost and low power consumption, and can be used in application systems such as member consumption points inquiry and medical treatment inquiry.

1 System Design

The magnetic stripe card information terminal is based on ARM single-chip microcomputer and μC/OS-Ⅱ real-time operating system. μC/OS-Ⅱ is an open source real-time operating system written by Jean J. Labrosse. However, μC/OS-Ⅱ only provides an operating system kernel, and does not provide support for network protocol stack, file system, etc. By transplanting the open source embedded TCP/IP protocol stack LwIP on the μC/OS-II operating system and using Siemens GPRS module MC39i, wireless Internet access can be achieved. The overall system block diagram is shown in Figure 1.

2 Hardware Design

The block diagram of the system hardware is shown in Figure 2. The system is based on the ARM microcontroller, which mainly includes NXP's microcontroller LPC2106/01, GPRS wireless MODEM MC39i, magnetic stripe card interface chip BS100E, keyboard and LCD module, etc.

NXP's LPC2106/01 microcontroller is a high-performance 32-bit RISC microprocessor based on the ARM7TDMI core. LPC2106 embeds 128 KB of in-system programmable FLASH and 64 KB of SR-AM, and integrates multiple 32-bit timers, PWM outputs, 2 UARTs interfaces and 32 GPIOs. The maximum CPU clock frequency supported by LPC2106 is 60 MHz.

The GPRS MODEM uses Siemens' MC39i. MC39i is a dual-band GSM/GPRS module that supports the standard ITU-TAT command set and GPRS Class 10 functions. It has the advantages of low power consumption and simple interface. The MC39i module requires an external SIM card holder and antenna. The UART1 interface of LPC2106 is connected to the data serial port of the MC39i module, and the MC39i module is triggered by the IGT signal.

The data recording format on the magnetic stripe card adopts the ISO7811 international standard and contains up to 3 tracks. In most applications, only track 2 information is used. The magnetic stripe card interface of the system consists of a magnetic head and an interface chip. The magnetic stripe card interface chip uses the single-track F2F decoding chip BS100E from Taiwan Vikintek, which can amplify the head signal and recover the F2F encoded data. The MSIA+ and MSIA- pins of BS100E are connected to the head output; the CLS (Card Load Signal) pin is the card swipe valid signal of the magnetic stripe card, the signal is valid at low level, and is connected to the external interrupt IO port of LPC2106; RDPA and RCPA are the data signal and clock signal of the decoded output respectively, RDPA is connected to the GPIO port of LPC2106, and RC-PA is connected to the external interrupt IO port of LPC2106. RCPA is set to trigger the interrupt on the rising edge.