GSM (Global System for Mobile communication) is a digital mobile telephony system. GSM digitizes and compresses data, then sends it down a channel with two other streams of user data, each in its own time slot. It demonstrate the principle of interfacing GSM with ARM LPC2148 microcontroller. It operates at either the 900 MHz or 1800 MHz frequency band. There are various GSM modules available in market like SIM900, SIM700, SIM800, SIM808, SIM5320 etc.SIM900A module allows users to send/receive data over GPRS, send/receive SMS and make/receive voice calls. It communicates serially with the devices like microcontroller, PC using AT commands. To interface SIM900A module with cellular network, it requires SIM card provided by a network operator.

ARM is a family of instruction set architectures for computer processors based on a reduced instruction set computing (RISC) architecture developed by British company ARM Holdings .A RISC-based computer design approach means ARM processors require significantly fewer transistors than typical processors in average computers. This approach reduces costs, heat and power use. These are desirable traits for light, portable, battery-powered devices including smartphones, laptops, tablet and notepad computers and other embedded systems. A simpler design facilitates more efficient multi-core CPUs and higher core counts at lower cost, providing higher processing power and improved energy efficiency for servers and supercomputers.

The ARM LPC2148 features are as follows:

1. Architecture: ARM v4T

2. Processor: ARM7-TDMI-S

3. Instructions: 32-bit ARM and 16-bit Thumb

4. Debug support: RT Embedded ICE, Embedded Trace interface

5. Static RAM: 32 KB

6. (On-chip)Additional: 8 KB for USB DMA

7. Flash Program: 512 KB

8. Mem.(On-chip)Programming: ISP/IAP via on-chip boot-loader program

9. GPIO No. of pins: up to 45 (fast GPIO lines, 5V tolerant), Configurable to fast GPIO

10. External Interrupts: Four; No. of pins: Nine

The ARM LPC2148 has two ports Port 0 and Port 1 respectively each port contains 32-bits for I/O operations. The Port 0 has 32-bit of I/O pins for individual directions and Port 1 has 32-bits of I/O pins for bidirectional purpose. It has two timers of each 32-bit. It has capable to storing 128-bit memory for interfacing.

Over the last few years, the ARM architecture has become the most pervasive 32-bitarchitecture in the world, with wide range of ICs available from various IC manufacturers. ARM processors are embedded in products ranging from cell/mobile phones to automotive braking systems. A worldwide community of ARM partners and third-party vendors has developed among semiconductor and product design companies, including hardware engineers, system designers, and software developers.

The ARM7 (LPC2148) is a 32 bit microcontroller and it supports two serial ports. The GSM module communicates to the microcontroller with mobile phones through UART. GSM modem  interfaces with microcontroller for SMS control of industrial equipments. Sending an SMS through GSM modem when interfaced with microcontroller or PC is much simpler as compared  to sending an SMS through UART. Text messages may be sent through the modem by interfacing only three signals of the serial interface of modem with microcontroller i.e., TxD, RxD and GND. In this scheme, RTS and CTS signals of serial port interface of GSM Modem are connected with each other.

The transmit and receive signals of the microcontroller serial port are connected to the corresponding signals of the serial interface of GSM module. The SMS message in text mode can contain only up to 140 characters. It depends upon the amount of information collected from GPS Engine that you need at the base station for tracking a vehicle or a person. Display text in mobile from LPC2148 kit by using GSM module through UART. The entire LPC2148 kit contains two serial interfaces that are UART0 & UART1.  The Interfacing GSM module with LPC2148 program is very simple and straight forward, which send a message to mobiles from LPC2148 Primer Board through GSM module by using UART0. Some delay is occurring when a single data is sent to mobile through UART.

The transmit and receive signals of the microcontroller serial port are connected to the corresponding signals of the serial interface of GSM module. The SMS message in text mode can contain only up to 140 characters. It depends upon the amount of information collected from GPS Engine that you need at the base station for tracking a vehicle or a person.

Display text in mobile from LPC2148 kit by using GSM module through UART. The entire LPC2148 kit contains two serial interfaces that are UART0 & UART1. The Interfacing GSM module with LPC2148 program is very simple and straight forward, which send a message to mobiles from LPC2148 Primer Board through GSM module by using UART0. Some delay is occurring when a single data is sent to mobile through UART. The interface is with a PIC microcontroller rated at 5V or a low rating which may not match exactly with the GPS modem. Therefore, there is a need to design additional power supply unit – other than the microcontroller power supply unit. Such a designing process includes rectification, filtration and regulation of units to obtain a regulated DC supply from the mains AC supply.

• Improved spectrum efficiency

• International roaming

• Support for new services.

• SIM phonebook management

• Compatibility with integrated services digital network (ISDN)