ADVANCED ATM SECURITY USING MEMS AND GSM
Chapter 1 Embedded Systems 1.1 INTRODUCTION TO EMBEDDED SYSTEMS Each day, our lives become more dependent on 'embedded systems', digital information technology that is embedded in our environment. More than 98% of processors applied today are in embedded systems, and are no longer visible to the customer as 'computers' in the ordinary sense. An Embedded System is a special-purpose system in which the computer is completely encapsulated by or dedicated to the device or system it controls. Unlike a general-purpose computer, such as a personal computer, an embedded system performs one or a few pre-defined tasks, usually with very specific requirements. Since the system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product. Embedded systems are often mass-produced, benefiting from economies of scale. The increasing use of PC hardware is one of the most important developments in high-end embedded systems in recent years. Hardware costs of high-end systems have dropped dramatically as a result of this trend, making feasible some projects which previously would not have been done because of the high cost of non-PC-based embedded hardware. But software choices for the embedded PC platform are not nearly as attractive as the hardware. Typically, an embedded system is housed on a single microprocessor board with the programs stored in ROM. Virtually all appliances that have a digital interface -- watches, microwaves, VCRs, cars -- utilize embedded systems. Some embedded systems include an operating system, but many are so specialized that the entire logic can be implemented as a single program. Physically, Embedded Systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants.
In terms of complexity embedded systems can range from very simple with a single microcontroller chip, to very complex with multiple units, peripherals and networks mounted inside a large chassis or enclosure. Definition of an Embedded System Embedded system is defined as, For a particular/specific application implementing the software code to interact directly with that particular hardware what we built. Software is used for providing features and flexibility, Hardware = {Processors, ASICs, Memory,...} is used for Performance (& sometimes security) (or) An embedded system is a special-purpose computer system designed to perform one or a few dedicated functions, often with real-time computing constraints. It is usually embedded as part of a complete device including hardware and mechanical parts. In contrast, a generalpurpose computer, such as a personal computer, can do many different tasks depending on programming. (or) An embedded system is a single-purpose computer built into a larger system for the purposes of controlling and monitoring the system. A specialized computer system that is part of a larger system or machine. There are many definitions of embedded system but all of these can be combined into a single concept. An embedded system is a special purpose computer system that is used for particular task. Features of Embedded Systems The versatility of the embedded computer system lends itself to utility in all kinds of enterprises, from the simplification of deliverable products to a reduction in costs in their development and manufacture. Complex systems with rich functionality employ special operating systems that
take into account major characteristics of embedded systems. Embedded operating systems have minimized footprint and may follow real-time operating system specifics. The special computers system is usually less powerful than general-purpose systems, although some expectations do exist where embedded systems are very powerful and complicated. Usually a low power consumption CPU with a limited amount of memory is used in embedded systems. Many embedded systems use very small operating systems; most of these provide very limited operating system capabilities. Since the embedded system is dedicated to specific tasks, design engineers can optimize it, reducing the size and cost of the product, or increasing the reliability and performance. Some embedded systems are mass-produced, benefiting from economies of scale. Some embedded systems have to operate in extreme environment conditions such as very high temperature & humidity. For high volume systems such as portable music players or mobile phones, minimizing cost is usually the primary design consideration. Engineers typically select hardware that is just “good enough” to implement the necessary functions. For low volume or prototype embedded systems, general purpose computers may be adapted by limiting the programs or by replacing the operating system with a real-time operating system. Characteristics of Embedded Systems
Embedded computing systems generally exhibit rich functionality—complex functionality is usually the reason for introducing CPUs into the design. However, they also exhibit many nonfunctional requirements that make the task especially challenging:
• real-time deadlines that will cause system failure if not met; • multi-rate operation;
• in many cases, low power consumption; • low manufacturing cost, which often means limited code size. Workstation programmers often concentrate on functionality. They may consider the performance characteristics of a few computational kernels of their software, but rarely analyze the total application. They almost never consider power consumption and manufacturing cost. The need to juggle all these requirements makes embedded system programming very challenging and is the reason why embedded system designers need to understand computer architecture. Overview of an Embedded System Architecture Every Embedded system consists of a custom-built hardware built around a central processing unit. This hardware also contains memory chips onto which the software is loaded.
Operating Application Software System H/W
The operating system runs above the hardware and the application software runs above the operating system. The same architecture is applicable to any computer including desktop
computer. However these are significant differences. It is not compulsory to have an operating system in every embedded system. For small applications such as remote control units, air conditioners, toys etc. Applications of Embedded Systems Some of the most common embedded systems used in everyday life are Small embedded controllers:
8-bit CPUs dominate, simple or no operating system (e.g., thermostats)
Control systems:
Often use DSP chip for control computations (e.g., automotive engine control)
Distributed embedded control: Mixture of large and small nodes on a real-time Embedded networks (e.g., cars, elevators, factory automation) System on chip:
ASIC design tailored to application area (e.g., consumer electronics, set-top boxes)
Network equipment:
Emphasis on data movement/packet flow (e.g., network switches; telephone switches)
Critical systems:
Safety and mission critical computing (e.g., pacemakers, automatic trains)
Signal processing:
Often use DSP chips for vision, audio, or other signal Processing (e.g., face recognition)
Robotics:
Uses various types of embedded computing (especially Vision and control) (e.g., autonomous vehicles)
Computer peripherals:
Disk drives, keyboards, laser printers, etc.
Wireless systems:
Wireless network-connected “sensor networks” and
“Motes” to gather and report information Embedded PCs:
Palmtop and small form factor PCs embedded into Equipment
Command and control:
Often huge military systems and “systems of systems” (e.g., a fleet of warships with interconnected Computers)
Home Appliances, intercom, telephones, security systems, garage door openers, answering machines, fax machines, home computers, TVs, cable TV tuner, VCR, camcorder, remote controls, video games, cellular phones, musical instruments, sewing machines, lighting control, paging, camera, pinball machines, toys, exercise equipment Office Telephones, computers, security systems, fax machines, microwave, copier, laser printer, color printer, paging Auto Trip computer, engine control, air bag, ABS, instrumentation, security system, transmission control, entertainment, climate control, cellular phone, keyless entry TYPES OF EMBEDDED SYSTEMS Based on functionality and performance embedded systems categorized as 4 types 1. Stand alone embedded systems 2. Real time embedded systems 3. Networked information appliances 4. Mobile devices
1. Stand alone embedded systems:As the name implies, stand alone systems work in stand alone mode. They take i/p, process them and produce the desire o/p. The i/p can be an electrical signal from transducer or temperature signal or commands from human being. The o/p can be electrical signal to drive another system an led or lcd display
ex digital camera, microwave oven, CD player, Air conditioner etc
2. Real time embedded systems:-
In this type of an embedded system a specific work has to be complete in a particular period of time. Hard Real time systems:- embedded real time used in missiles Soft Real time systems:- DVD players 3. Networked information appliances:Embedded systems that are provided with n/w interfaces and accessed by n/w's such as local area n/w or internet are called Network Information Appliances Ex A web camera is connected to the internet. Camera can send pictures in real time to any computers connected to the internet
4. Mobile devices:Actually it is a combination of both VLSI and Embedded System Mobile devices such as Mobile phone, Personal digital assistants, smart phones etc are special category of embedded systems
2.2 Introduction to Microcontroller Based on the Processor side Embedded Systems is mainly divided into 3 types 1. Micro Processor : - are for general purpose eg: our personal computer 2. Micro Controller:- are for specific applications, because of cheaper cost we will go for these 3. DSP ( Digital Signal Processor ):- are for high and sensitive application purpose
MICROCONTROLLER VERSUS MICROPROCESSOR A system designer using a general-purpose microprocessor such as the Pentium or the 68040
must add RAM, ROM, I/O ports, and timers externally to make them functional. Although the addition of external RAM, ROM, and I/O ports makes these systems bulkier and much more expensive, they have the advantage of versatility such that the designer can decide on the amount of RAM, ROM and I/O ports needed to fit the task at hand. A Microcontroller has a CPU (a microprocessor) in addition to a fixed amount of RAM, ROM, I/O ports, and a timer all on a single chip. In other words, the processor, the RAM, ROM, I/O ports and the timer are all embedded together on one chip; therefore, the designer cannot add any external memory, I/O ports, or timer to it. The fixed amount of on-chip ROM, RAM, and number of I/O ports in Microcontrollers makes them ideal for many applications in which cost and space are critical.
CPU platform: Embedded processors can be broken into two distinct categories: microprocessors (μP) and microcontrollers (μC). Microcontrollers have built-in peripherals on the chip, reducing size of the system. There are many different CPU architectures used in embedded designs such as ARM, MIPS, Coldfire/68k, PowerPC, x86, PIC, 8051, Atmel AVR, Renesas H8, SH, V850, FR-V, M32R, Z80, Z8, etc. This in contrast to the desktop computer market, which is currently limited to just a few competing architectures.
PC/104 and PC/104+ are a typical base for small, low-volume embedded and ruggedized system design. These often use DOS, Linux, NetBSD, or an embedded real-time operating system such as QNX or VxWorks. A common configuration for very-high-volume embedded systems is the system on a chip (SoC), an application-specific integrated circuit (ASIC), for which the CPU core was purchased and added as part of the chip design. A related scheme is to use a field-programmable gate array (FPGA), and program it with all the logic, including the CPU. Embedded systems are based on the concept of the microcontroller, a single integrated circuit that contains all the technology required to run an application. Microcontrollers make integrated systems possible by combining several features together into what is effectively a complete computer on a chip, including: * Central Processing Unit * Input/Output interfaces (such as serial ports) * Peripherals (such as timers) * ROM, EEPROM or Flash memory for program storage * RAM for data storage * Clock generator By integrating all of these features into a single chip it is possible to greatly reduce the number of chips and wiring necessary to control an electronic device, dramatically reducing its complexity, size and cost. * Size & Weight: Microcontrollers are designed to deliver maximum performance for minimum size and weight. A centralized on-board computer system would greatly outweigh a collection of microcontrollers. * Efficiency: Microcontrollers are designed to perform repeated functions for long periods of time without failing or requiring service. MICRO CONTROLLER: is a chip through which we can connect many other devices and also those are controlled by the program the program which burn into that chip
INTRODUCTION TO 8051 Intel Corporation introduced an 8 bit micro controller called the 8051 in 1981. While the time of introduction, Intel was given some specific features and particular name as
MCS-51
Features:ROM ---- 4 K bytes of Memory RAM ----- 128 bytes Timers------2 4 ports --- 32 I/O ports ( each 8 bit wide ) Interrupts-----6 serial port-----1 all on a single chip Many semiconductor manufacturers started either manufacturing the 8051 devices as such (Intel was liberal in giving away license to whoever asked) or developing a new kind of microcontrollers based on 8051 core architecture. Manufacturers modified the basic 8051 architecture and added many new peripheral functions to make them attractive to the designers. After that so many industries are come into picture to introduce 8051 again wit some extra features. This has led to many versions of the 8051 with different speeds and amounts of on-chip ROM marketed by more manufactures those are Dallas ------ DS4700 Zilog---------Z Motrolla Freescale Atmel ------- AT89C51/52, AT89S51/52 Phillips ----- P89C51RD2Fn Before these industries came into picture 8051 chips are made with CMOs technology. ATmel
was introduced with ISP (In System Programming)
In System Programming (ISP):In-System Programming (ISP) is the ability of some programmable logic devices, microcontrollers, and other programmable electronic chips to be programmed while installed in a complete system, rather than requiring the chip to be programmed prior to installing it into the system. (or) In-system programming is a valuable feature that allows system firmware to be upgraded without disassembling the embedded system to physically replace memory. Most Maxim 8051-based microcontrollers can be reprogrammed from a PC or laptop via an inexpensive RS-232 serial interface and a few logic gates The primary advantage of this feature is that it allows manufacturers of electronic devices to integrate programming and testing into a single production phase, rather than requiring a separate programming stage prior to assembling the system. This may allow manufacturers to program the chips in their own system's production line instead of buying preprogrammed chips from a manufacturer or distributor, making it feasible to apply code or design changes in the middle of a production run. 2.3 AT89S52 MICROCONTROLLER The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes of in-system programmable Flash memory. The device is manufactured using Atmel’s high-density nonvolatile memory technology and is compatible with the industry-standard 80C51 instruction set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with insystem programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerful microcontroller which provides a highly-flexible and cost-effective solution to many embedded control applications.
8051 PIN DIAGRAM
AT89S52 Architecture consists of these specific features: 8 bit CPU with registers A (Accumulator) and B 16 bit Program Counter(PC) and Data Pointer (DPTR) 8 bit Program Status Word (PSW)
8 bit Stack Pointer (SP) Internal ROM of 8k Internal RAM of 128 bytes Four Register banks each containing eight registers Sixteen bytes, which may be addressed at the bit level Eighty bytes of general purpose data memory 32 I/O pins arranged as four 8-bit ports: P0,P1,P2,P3 Two 16-bit Timers/Counters: T0 and T1 Full duplex serial data Receiver/Transmitter : SBUF Control Registers: TCON, TMOD, SCON, SMOD, PCON, IP and IE.
Two external and three internal interrupt sources. Oscillator and Clock circuits. Pin Description Pin ( 32 – 39 ) Port 0: Port 0 is an 8-bit open drain bidirectional port. As an open drain output port, it can sink eight LS TTL loads. Port 0 pins that have 1s written to them float, and in that state will function as high impedance inputs. Port 0 is also the multiplexed low-order address and data bus during accesses to external memory. In this application it uses strong internal pull ups when emitting 1s. Port 0 emits code bytes during program verification. In this application, external pull ups are required. Pin ( 1- 8 ) Port 1: Port 1 is an 8-bit bidirectional I/O port with internal pull ups. Port 1 pins that have 1s written to them are pulled high by the internal pull ups, and in that state can be used as inputs. As inputs, port 1 pins that are externally being pulled low will source current because of the internal pull ups. Alternate Functions of Port 1 used for In system Programmable P.5
MOSI --------- Instruction Input
P.6
MISO ---------- Data Output
P.7
SCK ----------- Clk in
Pin ( 21 – 28 ) Port 2:
Port 2 is an 8-bit bidirectional I/O port with internal pull ups. Port 2
emits the high-order address byte during accesses to external memory that use 16-bit addresses. In this application, it uses the strong internal pull ups when emitting 1s. Pin (10 – 17) Port 3: Port 3 is an 8-bit bidirectional I/O port with internal pull ups. It also serves the functions of various special features of the 80C51 Family as follows: Port Pin Alternate Function P3.0- RxD (serial input port) P3.1 -TxD (serial output port) P3.2 -INT0 (external interrupt 0) P3.3- INT1 (external interrupt 1) P3.4 -T0 (timer 0 external input) P3.5 -T1 (timer 1 external input) P3.6 -WR (external data memory write strobe) P3.7 -RD (external data memory read strobe) Pin 40 VCC: -Supply voltage Pin 20 VSS: -Circuit ground potential Pin 29 PSEN: Program Store Enable is the read strobe to external Program Memory. When the device is executing out of external Program Memory, PSEN is activated twice each machine
cycle (except that two PSEN activations are skipped during accesses to external Data Memory). PSEN is not activated when the device is executing out of internal Program Memory. Pin 30 ALE/PROG: Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory. ALE is emitted at a constant rate of 1/6 of the oscillator frequency, for external timing or clocking purposes, even when there are no accesses to external memory. (However, one ALE pulse is skipped during each access to external Data Memory.) This pin is also the program pulse input (PROG) during EPROM programming. Pin 31 EA/VPP: When EA is held high the CPU executes out of internal Program Memory. Holding EA low forces the CPU to execute out of external memory regardless of the Program Counter value. In the 80C31, EA must be externally wired low. In the EPROM devices, this pin also receives the programming supply voltage (VPP) during EPROM programming. Pin 18 XTAL1: Input to the inverting oscillator amplifier. Pin 19 XTAL2: Output from the inverting oscillator amplifier.
REGISTERS 8051 is a collection of 8 and 16 bit registers and 8 bit memory locations. These registers and memory locations can be made to operate using the software instructions. The program instructions control the registers and digital data paths that are contained inside the 8051, as well as memory locations that are located outside the 8051. Register are used to store information temporarily, while the information could be a byte of data to be processed, or an address pointing to the data to be fetched. The vast majority of 8051 register are 8-bit registers. Generally there are two types of registers. They are General purpose Registers (GPR’s) and Special Function Registers (SFR’s)
General Purpose Register
The 8 bits of a register are shown from MSB D7 to the LSB D0. With an 8-bit data type, any data larger than 8 bits must be broken into 8-bit chunks before it is processed.
The most widely used registers A (Accumulator)
For all arithmetic and logic instructions B, R0, R1, R2, R3, R4, R5, R6, R7 DPTR (data pointer), and PC (program counter)
16 – bit General Purpose Register are Data Pointer (DPTR) and Program Counter (PC) The program counter points to the address of the next instruction to be executed. DPTR. As the name suggests, is used to point the data. It is used by a number of commands which allows the microcontroller to access external memory. When the microcontroller access external memory it will access at the address indicated by DPTR.
There are 128 bytes of RAM in the 8051 The 128 bytes are divided into three different groups as follows: 1) A total of 32 bytes from locations 00 to 1F hex are set aside for register banks and the stack 2) A total of 16 bytes from locations 20H to 2FH are set aside for bit-addressable read/write memory 3) A total of 80 bytes from locations 30H to 7FH are used for read and write storage, called scratch pad
Special Function Registers The program status word (PSW) PSW register, also referred to as the flag register, is an 8 bit register Only 6 bits are used These four are CY (carry), AC (auxiliary carry), P (parity), and OV (overflow) They are called conditional flags, meaning that they indicate some conditions that resulted after an instruction was executed. The PSW3 and PSW4 are designed as RS0 and RS1, and are used to change the bank. The two unused bits are user-definable
–
2.4 Timer/Counters The Atmel 80C51 Microcontrollers implement two general purpose, 16-bit timers/ counters. They can be used either as timers to generate a time delay or as a counter to count events happening outside the microcontroller. The microcontroller has two 16-bit wide timers. They are identified as Timer 0 and Timer 1, and can be independently configured to operate in a variety of modes as a timer or as an event counter. When operating as a timer, the timer/counter runs for a programmed length of time, then issues an interrupt request. When operating as a counter, the timer/counter counts negative transitions on an external pin. After a preset number of counts, the
counter issues an interrupt request. Register pairs (TH0, TL0), (TH1, TL1), and (TH2, TL2) are the 16-bit counting registers for Timer/Counters 0, 1, and 2, respectively. Timer 0 Register The 16-bit register of Timer 0 is accessed as low byte and high byte. The low byte register is called TL0 (Timer 0 low byte) and high byte register is referred to as TH0 (Timer 0 high byte). These registers can be accessed like any other register, such as A,B,R0,R1,R2,etc. Timer 1 Register Timer 1 is also 16-bits, and its 16-bit register is split into two bytes, referred to as TL1 ( Timer 1 low byte ) and TH1 ( Timer 1 high byte ). These registers are accessible in the same way as the registers of timer 0. TMOD Register (timer mode) TMOD: Timer/Counter Mode Control Register. Not Bit Addressable.
Timer 1
Timer 0
GATE When TRx (in TCON) is set and GATE=1, Timer/CounterX will run only while INTx pin is high (hardware control). When GATE=0,
Timer/Counter will
run only while TRx=1 (software control). C/T
Timer or Counter selector. Cleared for Timer operation (input from internal system clock). Set for Counter operation
M1
Mode selector bit.
M0
Mode selector bit.
(input from TX input pin).
M1
M0
Mode
Operating Mode
0
0
0
13-bit Timer (8048 compatible) (TH1)
0
1
1
16-bit Timer/Counter
1
0
2
8-bit Auto-Reload Timer/Counter (TL1). Reloaded from TH1 at overflow.
1 1
1
3 1
timer 1 halted. Retains count. 3
(Timer 1) Timer/Counter 1 stopped.
TCON: Timer/Counter Control Register Bit Addressable.
The upper four
The lower 4 bits
bits are used to
are set aside for
store the TF and
controlling the
TR bits of both
TF1
Timer1 overflow flag. Set by hardware when the Timer/Counter 1 overflows. Cleared by hardware as processor vectors to the interrupt service routine.
TR1
Timer 1 run control bit. Set/cleared by software to turn Timer/Counter 1 ON/OFF.
TF0
Timer0 overflow flag. Set by hardware when the Timer/Counter 0 overflows. Cleared by hardware as processor vectors to the service routine.
TR0 IE1
Timer 0 run control bit. Set/cleared by software to turn Timer/Counter 0 ON/OFF. External Interrupt 1 edge flag. Set by hardware when External terrupt edge is detected. Cleared by hardware when interrupt is processed.
IT1
Interrupt 1 type control bit. Set/cleared by software to specify falling edge/low level triggered External Interrupt.
IE0
External Interrupt 0 edge flag. Set by hardware when External Interrupt
edge is
detected. Cleared by hardware when interrupt is processed. IT0
Interrupt 0-type control bit. Set/cleared by software to specify falling edge/low level triggered External Interrupt.
2.5 SERIAL COMMUNICATION
The 8051 serial port is full duplex. In other words, it can transmit and receive data at the same time. Unlike any other register in the 8051, SBUF is in fact two distinct registers - the write-only register and the read-only register. Transmitted data is sent out from the write-only register while received data is stored in the read-only register. There are two separate data lines, one for transmission (TXD) and one for reception (RXD). Therefore, the serial port can be transmitting data down the TXD line while it is at the same time receiving data on the RXD line. The TXD line is pin 11 of the microcontroller (P3.1) while the RXD line is on pin 10 (P3.0)
Serial data communication uses two methods, asynchronous and synchronous. The synchronous method transfers a block of data (characters) at a time, while the asynchronous method transfers a single byte at a time. It is possible to write software to use either of these methods, but the programs can be tedious and long. For this reason, there are special IC chips made by many manufacturers for serial data communications. These chips can be commonly referred to as UART (Universal Asynchronous Receiver-transmitter) and USART Asynchronous Receiver-Transmitter). The 8051 chip has a built-in UART. Asynchronous Serial Communication and Data Framing Start Bits and Stop Bits
( Universal Synchronous
In the asynchronous method is character is placed between start and stop bits, this is called data framing. In asynchronous communication, at least two extra bits are transmitted with the data word; a start bit and a stop bit. Therefore, if the transmitter is using an 8-bit system, the actual number of bits transmitted per word is ten. In most protocols the start bit is a logic 0 while the stop bit is logic 1. Therefore, when no data is being sent the data line is continuously HIGH. The receiver waits for a 1 to 0 transition. In other words, it awaits a transition from the stop bit (no data) to the start bit (logic 0). Once this transition occurs the receiver knows a data byte will follow. Since it knows the data rate (because it is defined in the protocol) it uses the same clock as frequency as that used by the transmitter and reads the correct number of bits and stores them in a register. For example, if the protocol determines the word size as eight bits, once the receiver sees a start bit it reads the next eight bits and places them in a buffer. Once the data word has been read the receiver checks to see if the next bit is a stop bit, signifying the end of the data. If the next bit is not a logic 1 then something went wrong with the transmission and the receiver dumps the data. If the stop bit was received the receiver waits for the next data word, ie; it waits for a 1 to 0 transition.
Goes out first
Baud Rates in the 8051
11.0592 MHz
XTAL oscillat or
Machine
?12
cycle frequency 921.6 kHz
28800 ?32 Hz To timer Timer 1 By UART 1 To set the Baud rate
XTAL = 11.0592 MHz: The frequency of system clock = 11.0592 MHz / 12 = 921.6 kHz The frequency sent to timer 1 = 921.6 kHz/ 32 = 28,800 Hz (a) 28,800 / 3 = 9600
where -3 = FD (hex) is loaded into TH1
(b) 28,800 / 12 = 2400 where -12 = F4 (hex) is loaded into TH1 (c) 28,800 / 24 = 1200 where -24 = E8 (hex) is loaded into TH1
SBUF SBUF is an 8-bit register used solely for serial communication in the 8051. For a byte of data to be transferred via the TxD line, it must be placed in the SBUF register. Similarly, SBUF holds the byte of data when it is received by the 8051’s RxD line. SBUF can be accessed like any other register in the 8051. The moment a byte is written into SBUF, it is framed with the start and stop bits and transferred serially via the TxD pin. Similarly, when the bits are received serially via RxD, the 8051 deframes it by eliminating the stop and start bits, making a byte out of the data received, and then placing it in the SBUF. DATA TRANSMISSION: Transmission of serial data bits begins anytime data is written to sbuf. " TI " (SCON) set to 1 when data has been transmitted and signifies that " SBUF " is empty and that another data byte can be sent. DATA RECEPTION: Reception of serial data will begin if the receive enable bit (REN) in SCON is set to ' 1 ' for all modes. For mode ' 0 ' only RI must be cleared to 0. Receiver interrupt flag ' RI ' (in
SCON) is set after data has been received in all modes. Setting of ' REN ' bit is a direct program control that limits the reception of unexpected data.
SCON ( Serial Control ) Register
SM0
SM1
SM2
REN
TB8
RB8
TI
RI
Mode 0: Serial data enters and exits through RxD. TxD outputs the shift clock. 8 bits are transmitted/received (LSB first). The baud rate is fixed at 1/12 the oscillator frequency.
Mode 1: 10 bits are transmitted (through TxD) or received (through RxD): a start bit (0), 8 data bits (LSB first), and a stop bit (1). On receive, the stop bit goes into RB8 in Special Function Register SCON. The baud rate is variable. Mode 2: 11 bits are transmitted (through TxD) or received (through RxD): start bit (0), 8 data bits (LSB first), a programmable 9th data bit, and a stop bit (1). On Transmit, the 9th data bit (TB8 in SCON) can be assigned the value of 0 or 1. Or, for example, the parity bit (P, in the PSW) could be moved into TB8. On receive, the 9th data bit goes into RB8 in Special Function Register SCON, while the stop bit is ignored. The baud rate is programmable to either 1/32 or 1/64 the oscillator frequency. Mode 3: 11 bits are transmitted (through TxD) or received (through RxD): a start bit (0), 8 data bits (LSB first), a programmable 9th data bit, and a stop bit (1). In fact, Mode 3 is the same as Mode 2 in all respects except baud rate. The baud rate in Mode 3 is variable. In all four modes, transmission is initiated by any instruction that uses SBUF as a destination register. Reception is initiated in Mode 0 by the condition RI = 0 and REN = 1. Reception is initiated in the other modes by the incoming start bit if REN = 1. SM2 Enables the multiprocessor communication feature in Modes 2 and 3. In Mode 2 or 3, if SM2 is set to 1, then Rl will not be activated if the received 9th data bit (RB8) is 0. In Mode 1, if SM2=1 then RI will not be activated if a valid stop bit was not received. In Mode 0, SM2 should be 0.
REN Enables serial reception. Set by software to enable reception. Clear by software to disable reception. TB8 The 9th data bit that will be transmitted in Modes 2 and 3. Set or clear by software as desired. RB8 In Modes 2 and 3, is the 9th data bit that was received. In Mode 1, it SM2=0, RB8 is the stop bit that was received. In Mode 0, RB8 is not used. TI (Transmit Interrupt)
This is an extremely important flag bit in the SCON register. When the 8051 finishes the transfer of the 8-bit character it raises the TI flag to indicate that it is ready to transfer another byte. The TI bit is raised at the beginning of the stop bit.
RI ( Receive Interrupt) This is an extremely important flag bit in the SCON register. When the 8051 receives data serially via RxD, it gets rid of the start and stop bits and places the byte in the SBUF register. Then it raises the RI flag bit to indicate that a byte has been received and chould be picked up before it is lost.
INTERRUPTS An interrupt is a special feature which allows the 8051 to provide the illusion of "multi-tasking," although in reality the 8051 is only doing one thing at a time. The word "interrupt" can often be substituted with the word "event." An interrupt is triggered whenever a corresponding event occurs. When the event occurs, the 8051 temporarily puts "on hold" the normal execution of the program and executes a special section of code referred to as an interrupt handler. The interrupt handler performs whatever special functions are required to handle the event and then returns control to the 8051 at which point program execution continues as if it had never been interrupted. Interrupt Service Routine For every interrupt, there must be an interrupt service routine (ISR). Or interrupt handler. When an interrupt is invoked, the microcontroller runs the interrupt service routine. For every interrupt, there is a fixed location in memory that holds the address of its ISR. The group of memory locations set aside to hold the addresses of the ISRs is called interrupt vector table.
Six Interrupts in 8051 1. Reset : When the reset pin is activated, the 8051 jumps to address location 0000 2. Two interrupts are set aside for the timers: one for the Timer 0 and one for Timer1. 3. Two interrupts are set aside for hardware external interrupts : one for INT0 and one for INT1 4. Serial communication has a single interrupt that belongs to both receive and transmit. Enabling Interrupt (IE) Register All interrupt are disabled after reset We can enable and disable them bye IE EA EA
-IE.7
ET2
ES
ET1
EX1
ET0
EX0
If EA=0, disables all interrupts, no interrupt is acknowledged If EA=1, each interrupt source is individually enabled or disabled by setting or clearing its enable bit.
--
IE.6
Not implemented, reserved for future use.
ET2
IE.5
Enables or disables Timer2 overflow or capture interrupt (8052 only)
ES
IE.4
Enables or disables the serial port interrupt.
ET1
IE.3
Enables or disables Timer 1 overflow interrupt.
EX1
IE.2
Enables or disables external interrupt 1.
ET0
IE.1
Enables or disables Timer 0 overflow interrupt.
EX0
IE.0
Enables or disables external interrupt 0.
Interrupt Priority (IP) Register 0= lower priority, 1= higher priority, reset IP=00H Lower priority ISR can be interrupted by a high priority interrupt. A high priority ISR can not be interrupted.
Low-priority interrupt wait until 8051 has finished servicing the high-priority interrupt.
--
--
PT2
PS
PT1
PX1
--
IP.7
Reserved
--
IP.6
Reserved
PT2
IP.5
Timer2 interrupt priority bit (8052 only)
PS
IP.4
serial port interrupt priority bit.
PT1
IP.3
Timer 1 interrupt priority bit.
PX1
IP.2
external interrupt 1 priority bit.
PT0
IP.1
Timer 0 interrupt priority bit.
PX0
IP.0
external interrupt 0 priority bit.
BASIC REQUIRMENT The following are the basic five requirements of microcontroller 1. Power Supply
PT0
PX0
2. Crystal Oscillator 3. Reset 4. SIP Resistor 5. Resistor for EA Pin 1. Regulated Power Supply
In mains-supplied electronic systems the AC input voltage must be converted into a DC voltage with the right value and degree of stabilization. The common DC voltages that are required to power up the devices are generally in the range of 3 VDC to 30 VDC. Typically the fixed types of DC voltages are 5V, 9V, 12V, 15V and 18V DC.
POWER SUPPLY MODULES:
•
STEP DOWN TRANSFORMER
•
BRIDGE RECTIFIER WITH FILTER
•
VOLTAGE REGULATORS
Transformer Transformers convert AC electricity from one voltage to another with little loss of power. Transformers work only with AC and this is one of the reasons why mains electricity is AC. Step-up transformers increase voltage, step-down transformers reduce voltage. A step down power transformer is used to step down the AC voltage from the line voltage of 110 VAC or 220 VAC i.e, it converts higher voltage at the input side to a lower voltage at the output.
Rectifier There are several ways of connecting diodes to make a rectifier to convert AC to DC. The bridge rectifier is the most important and it produces full-wave varying DC
Bridge rectifier Alternate pairs of diodes conduct, changing over
Output: full-wave varying DC (using all the AC wave)
the connections so the alternating directions of AC are converted to the one direction of DC. Filter Filtering is performed by a large value electrolytic capacitor connected across the DC supply to act as a reservoir, supplying current to the output when the varying DC voltage from the rectifier is falling. The diagram shows the unfiltered varying DC (dotted line) and the filtered DC (solid line). The capacitor charges quickly near the peak of the varying DC, and then discharges as it supplies current to the output.
Typically 1000 μf capacitor is used
Regulator This is a simple DC regulated supply project using 7805 voltage regulator to obtain a variable DC voltage range from 5V to 15V
Pin out of the 7805 regulator IC. 1. Unregulated voltage in 2. Ground 3. Regulated voltage out If you need other voltages than +5V, you can modify the circuit by replacing the 7805 chips with another regulator with different output voltage from regulator 78xx chip family. The last numbers in the the chip code tells the output voltage. Remember that the input voltage must be at least 3V greater than regulator output voltage ot otherwise the regulator does not work well. Crystal Oscillator The 8051 uses the crystal for precisely that: to synchronize it’s operation. Effectively, the 8051 operates using what are called "machine cycles." A single machine cycle is the minimum amount of time in which a single 8051 instruction can be executed. although many instructions take multiple cycles. 8051 has an on-chip oscillator. It needs an external crystal that decides the operating frequency of the 8051. The crystal is connected to pins 18 and 19 with stabilizing capacitors. 12 MHz (11.059MHz) crystal is often used and the capacitance ranges from 20pF to 40pF. A cycle is, in reality, 12 pulses of the crystal. That is to say, if an instruction takes one machine cycle to execute, it will take 12 pulses of the crystal to execute. Since we know the we can calculate how many instruction cycles the 8051 can execute per second: 11,059,000 / 12 = 921,583
11.0592 MHz crystals are often used because it can be divided to give you exact clock rates for most of the common baud rates for the UART, especially for the higher speeds (9600, 19200).
Reset RESET is an active High input When RESET is set to High, 8051 goes back to the power on state.The 8051 is reset by holding the RST high for at least two machine cycles and then returning it low. Initially charging of capacitor makes RST High, When capacitor charges fully it blocks DC.
SIP Resistor Sip Resistor is a single in pack Resistor (i.e.,) 8 resistors connected in series. Basically SIP resistor is a 9 pin connector first pin is for power supply to the entire 8 resistors in SIP. Generally SIP Resistor is used to close the open drain connections of Port 0.
Chapter 3 Block Diagram BLOCK DIAGRAM:
LCD 16 x 2
RPS
MICROCONTROLLER
ADC
AT89S52 Buzzer
Cryst al GSM MODEM
MAX 232
Accele romet er
DESCRIPTION:
Microelectromechanical systems (MEMS) is the technology of the very small, and merges at the nano-scale into nano- electromechanical systems (NEMS) and nanotechnology. MEMS are also referred to as micro-machines or Micro Systems Technology - MST. MEMS are made up of components between 1 to 100 micrometres in size and MEMS devices generally range in size from 20 micrometres to a millimetre. They usually consist of a central unit that processes data, the microprocessor and several components that interact with the outside such as microsensors. Due to MEMS large surface area to volume ratio, surface effects such as electrostatics and wetting dominate volume effects such as inertia or thermal mass. This property is used to detect any motion or change in acceleration due to gravity or simply called G force. The system needs to be secured and at the same time, should be protective for valuable items such that no body can try to theft our valuable items. The present project deals with designing an activation system for the protection of valuable items by checking the change in G force. If motion or change is detected the protection system is activated. In this project microcontroller is interfaced with mems sensor with accelerometer, buzzer and LCD. Microcontroller continuously monitors the mems sensor. Any change in x and y direction is detected the voltage level of the sensor varies which is an analog signal. ADC converts the analog signal to digital and is given to the microcontroller. When the microcontroller detects the change in the sensor the buzzer is switched on, the same is displayed on LCD and the GSM modem is used to send sms to the mobile number programmed in the microcontroller.
The system uses a compact circuitry build around flash version of at89s52 microcontroller with a non volatile memory Programs are developed using embedded c, compiled using ride tool. Isp is used to dump the code into microcontroller.
Chapter 3 HARDWARE IMPLEMENTATION Power Supply interface with microcontroller
The power supply consists of a 9-0-9 step down transformer. A bridge rectifier is used to rectify and convert AC to DC. A 1000uF capacitor is used to filter the ripples and the output is connected to 7805 voltage regulator. This comprises the power supply for the entire circuit. Vcc is connected to Pin 40 the power supply of microcontroller.
INTRODUCTION TO MEMs
Microelectromechanical systems (MEMS) is the technology of the very small and miniature systems and merges at the nano-scale into nanoelectromechanical systems (NEMS) and nanotechnology. MEMS are made up of components between 1 to 100 micrometres in size (i.e. 0.001 to 0.1 mm) and MEMS devices generally range in size from 20 micrometres (20 millionths of a metre) to a millimetre. They usually consist of a central unit that processes data, the microprocessor and several components that interact with the outside such as microsensors. At these size scales, the standard constructs of classical physics are not always useful. Due to MEMS' large surface area to volume ratio, surface effects such as electrostatics and wetting dominate volume effects such as inertia or thermal mass.
Micro-Electro-Mechanical Systems (MEMS) is the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. While the electronics are fabricated using integrated circuit (IC) process sequences (e.g., CMOS, Bipolar, or BICMOS
processes),
the
micromechanical
components
are
fabricated
using
compatible
"micromachining" processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices.
MEMS promises to revolutionize nearly every product category by bringing together silicon-based microelectronics with micromachining technology, making possible the realization of complete systems-on-a-chip. MEMS is an enabling technology allowing the development of smart products, augmenting the computational ability of microelectronics with the perception and control capabilities of microsensors and microactuators and expanding the space of possible designs and applications.
Microelectronic integrated circuits can be thought of as the "brains" of a system and MEMS augments this decision-making capability with "eyes" and "arms", to allow microsystems to sense and control the environment. Sensors gather information from the environment through measuring mechanical, thermal, biological, chemical, optical, and magnetic phenomena. The electronics then process the information derived from the sensors and through some decision making capability direct the actuators to respond by moving, positioning, regulating, pumping,
and filtering, thereby controlling the environment for some desired outcome or purpose. Because MEMS devices are manufactured using batch fabrication techniques similar to those used for integrated circuits, unprecedented levels of functionality, reliability, and sophistication can be placed on a small silicon chip at a relatively low cost.
APPLICATIONS
There are numerous possible applications for MEMS and Nanotechnology. As a breakthrough technology, allowing unparalleled synergy between previously unrelated fields such as biology and microelectronics, many new MEMS and Nanotechnology applications will emerge, expanding beyond that which is currently identified or known. Here are a few applications of current interest: Biotechnology MEMS and Nanotechnology is enabling new discoveries in science and engineering such as the Polymerase Chain Reaction (PCR) microsystems for DNA amplification and identification, micromachined Scanning Tunneling Microscopes (STMs), biochips for detection of hazardous chemical and biological agents, and microsystems for high-throughput drug screening and selection. Communications High frequency circuits will benefit considerably from the advent of the RF-MEMS technology. Electrical components such as inductors and tunable capacitors can be improved significantly compared to their integrated counterparts if they are made using MEMS and Nanotechnology. With the integration of such components, the performance of communication circuits will improve, while the total circuit area, power consumption and cost will be reduced. In addition, the mechanical switch, as developed by several research groups, is a key component with huge potential in various microwave circuits. The demonstrated samples of mechanical switches have quality factors much higher than anything previously available.
Reliability and packaging of RF-MEMS components seem to be the two critical issues that need to be solved before they receive wider acceptance by the market. Accelerometers MEMS accelerometers are quickly replacing conventional accelerometers for crash airbag deployment systems in automobiles. The conventional approach uses several bulky accelerometers made of discrete components mounted in the front of the car with separate electronics near the air-bag. MEMS and Nanotechnology has made it possible to integrate the accelerometer and electronics onto a single silicon chip at a 5-10 times lower cost. These MEMS accelerometers are much smaller, more functional, lighter, more reliable, and are produced for a fraction of the cost of the conventional macroscale accelerometer elements.
A/D CONVERTER An analog-to-digital converter (abbreviated ADC, A/D or A to D) is a device which converts continuous signals to discrete digital numbers. The reverse operation is performed by a digital-toanalog converter (DAC). Typically, an ADC is an electronic device that converts an input analog voltage (or current) to a digital number proportional to the magnitude of the voltage or current. However, some nonelectronic or only partially electronic devices, such as rotary encoders, can also be considered ADCs.
RESOLUTION The resolution of the converter indicates the number of discrete values it can produce over the range of analog values. The values are usually stored electronically in binary form, so the resolution is usually expressed in bits. In consequence, the number of discrete values available, or "levels", is usually a power of two. For example, an ADC with a resolution of 8 bits can encode an analog input to one in 256 different levels, since 28 = 256. The values can represent the ranges from 0 to 255 (i.e. unsigned integer) or from -128 to 127 (i.e. signed integer), depending on the application.
ACCURACY An ADC has several sources of errors. Quantization error and (assuming the ADC is intended to be linear) non-linearity is intrinsic to any analog-to-digital conversion. There is also a so-called aperture error which is due to a clock jitter and is revealed when digitizing a time-variant signal (not a constant value). These errors are measured in a unit called the LSB, which is an abbreviation for least significant bit. In the above example of an eight-bit ADC, an error of one LSB is 1/256 of the full signal range, or about 0.4%.
QUANTIZATION ERROR Quantization error is due to the finite resolution of the ADC, and is an unavoidable imperfection in all types of ADC. The magnitude of the quantization error at the sampling instant is between zero and half of one LSB. In the general case, the original signal is much larger than one LSB. When this happens, the quantization error is not correlated with the signal, and has a uniform distribution. Its RMS value is the standard deviation of this distribution, given by
. In the eight-bit ADC
example, this represents 0.113% of the full signal range. At lower levels the quantizing error becomes dependent of the input signal, resulting in distortion. This distortion is created after the anti-aliasing filter, and if these distortions are above 1/2 the sample rate they will alias back into the audio band. In order to make the quantizing error independent of the input signal, noise with an amplitude of 1 quantization step is added to the signal. This slightly reduces signal to noise ratio, but completely eliminates the distortion. It is known as dither.
SAMPLING RATE
The analog signal is continuous in time and it is necessary to convert this to a flow of digital values. It is therefore required to define the rate at which new digital values are sampled from the analog signal. The rate of new values is called the sampling rate or sampling frequency of the converter. A continuously varying bandlimited signal can be sampled (that is, the signal values at intervals of time T, the sampling time, are measured and stored) and then the original signal can be exactly reproduced from the discrete-time values by an interpolation formula. The accuracy is limited by quantization error. However, this faithful reproduction is only possible if the sampling rate is higher than twice the highest frequency of the signal. This is essentially what is embodied in the Shannon-Nyquist sampling theorem. Since a practical ADC cannot make an instantaneous conversion, the input value must necessarily be held constant during the time that the converter performs a conversion (called the conversion time). An input circuit called a sample and hold performs this task—in most cases by using a capacitor to store the analog voltage at the input, and using an electronic switch or gate to disconnect the capacitor from the input. Many ADC integrated circuits include the sample and hold subsystem internally.
MCP3208 (ADC) Description The Microchip Technology Inc. MCP3204/3208 devices are successive approximation 12-bit Analog to Digital (A/D) Converters with on-board sample and hold circuitry. The MCP3204 is programmable to provide two pseudo-differential input pairs or four single ended inputs. The MCP3208 is programmable to provide four pseudo-differential input pairs or eight single ended inputs. Differential Nonlinearity (DNL) is specified at ±1 LSB, while Integral Nonlinearity (INL) is offered in ±1 LSB (MCP3204/3208-B) and ±2 LSB (MCP3204/3208-C) versions.
Communication with the devices is accomplished using a simple serial interface compatible with the SPI protocol. The devices are capable of conversion rates of up to 100 ksps. The MCP3204/3208 devices operate over a broad voltage range (2.7V - 5.5V). Low current design permits operation with typical standby and active currents of only 500 nA and 320 μA, respectively.
MMA7260 (MEMs Sensor) The device consists of two surface micromachined capacitive sensing cells (g-cell) and a signal conditioning ASIC contained in a single integrated circuit package. The sensing elements are sealed hermetically at the wafer level using a bulk micromachined cap wafer. The g-cell is a mechanical structure formed from semiconductor materials (polysilicon) using semiconductor processes (masking and etching). It can be modeled as a set of beams attached to a movable central mass that move between fixed beams. The movable beams can be deflected from their rest position by subjecting the system to an acceleration.
As the beams attached to the central mass move, the distance from them to the fixed beams on one side will increase by the same amount that the distance to the fixed beams on the other side decreases. The change in distance is a measure of acceleration. The g-cell beams form two back-to-back capacitors. As the center beam moves with acceleration, the distance between the beams changes and each capacitor's
value will change, (C = Aε/D). Where A is the area of the beam, ε is the dielectric constant, and D is the distance between the beams. The ASIC uses switched capacitor techniques to measure the g-cell capacitors and extract the acceleration data from the difference between the two capacitors. The ASIC also signal conditions and filters (switched capacitor) the signal, providing a high level output voltage that is ratiometric and proportional to acceleration.
Global System for Mobile Communication (GSM)
Definition
Global system for mobile communication (GSM) is a globally accepted standard for digital cellular communication. GSM is the name of a standardization group established in 1982 to create a common European mobile telephone standard that would formulate specifications for a pan-European mobile cellular radio system operating at 900 MHz. A GSM modem is a wireless modem that works with a GSM wireless network. A wireless modem behaves like a dial-up modem. The main difference between them is that a dial-up modem sends and receives data through a fixed telephone line while a wireless modem sends and receives data through radio waves. A GSM modem can be an external device or a PC Card / PCMCIA Card. Typically, an external GSM modem is connected to a computer through a serial cable or a USB cable. A GSM modem in the form of a PC Card / PCMCIA Card is designed for use with a laptop computer. It should be inserted into one of the PC Card / PCMCIA Card slots of a laptop computer. Like a GSM mobile phone, a GSM modem requires a SIM card from a wireless carrier in order to operate. As mentioned in earlier sections of this SMS tutorial, computers use AT commands to control modems. Both GSM modems and dial-up modems support a common set of standard AT commands. You can use a GSM modem just like a dial-up modem.
In addition to the standard AT commands, GSM modems support an extended set of AT commands. These extended AT commands are defined in the GSM standards. With the extended AT commands, you can do things like: •
Reading, writing and deleting SMS messages.
•
Sending SMS messages.
•
Monitoring the signal strength.
•
Monitoring the charging status and charge level of the battery.
•
Reading, writing and searching phone book entries.
The number of SMS messages that can be processed by a GSM modem per minute is very low -- only about six to ten SMS messages per minute. GSM AT COMMANDS AT AT&D0 AT+IFC=00 ATCMGF=1 AT+CNMI=22000 AT commands features 1. Setting up your GSM modem
Most GSM modems comes with a simple manual and necessary drivers. To setup your T-ModemUSB, download the USB GSM Modem Quick Start ( Windows ) guide (460kB PDF). You would be able to send SMS from the
Windows application and also setup GPRS connectivity. The GSM modem will map itself as a COM serial port on your computer.
Windows based control panel to setup GSM modem, GPRS and send SMS 2.
Using the HyperTerminal
Hint :: By developing your AT commands using HyperTerminal, it will be easier for you to develop your actual program codes in VB, C, Java or other platforms. Go to START\Programs\Accessories\Communications\HyperTerminal (Win 2000) to create a new connection, eg. "My USB GSM Modem". Suggested settings :: -
COM
Port
::
As
indicated
in
the
T-Modem
Control Tool
- Bits per second :: 230400 ( or slower ) -Data Bits : 8 - Parity : NoneStopBitsFlowControl: HardwareYou are now ready to start working with AT commands. Type in "AT" and you should get a "OK", else you have not setup your HyperTerminal correctly. Check your port settings and also make sure your GSM modem
is
properly
3. Initial setup AT commands
connected
and
the
drivers
installed.
We are ready now to start working with AT commands to setup and check the status of the GSM modem. AT
Returns a "OK" to confirm that modem is working
AT+CPIN="xxxx" To enter the PIN for your SIM ( if enabled ) AT+CREG? AT+CSQ
A "0,1" reply confirms your modem is connected to GSM network Indicates the signal strength, 31.99 is maximum.
4. Sending
SMS
using
AT
commands
We suggest try sending a few SMS using the Control Tool above to make sure your GSM modem can send SMS before proceeding. Let's look at the AT commands involved .. AT+CMGF=1
To format SMS as a TEXT message
AT+CSCA="+xxxxx" Set your SMS center's number. Check with your provider. To send a SMS, the AT command to use is AT+CMGS.. AT+CMGS="+yyyyy"> Your SMS text message here The "+yyyyy" is your receipent's mobile number. Next, we will look at receivingSMSviaATcommands. GSM INTERFACE WITH MICROCONTROLLER
In this project GSM Modem is interfaced with the microcontroller through rs232 interface. Since the voltage levels of the microcontroller are different with that of the GSM modem we use a voltage converter or the line driver such as MAX232 to make them rs232 compatible.
RS232
The most popular serial communication standard for asynchronous communications is RS-232 (Recommended Standard – 232. This specifies the rule of how different connected devices communicate. The connected devices can either be terminals or communication equipments commonly referred as DTE & DCE.
According to RS232 interface, it requires only 3 lines i.e. Rx, Tx & Ground when compared to the bunch of connectors required for parallel communication. Even though parallel communication is easier to establish, serial communication is preferred based on the costs for the communication lines. The EIA (Electronics Industry Association) RS232C Standard specifies & suggests a maximum baud rate of 20,000bps, and RS232D is an advanced version of the same, which allows 1.5 Mbps. The connectors specified are D-TYPE 25 pin connector and D-TYPE 9 pin connector.
D-Type-25 pin no. Pin outs
Function
pin no. 3
2
RD
Receive Data (Serial data input)
2
3
TD
Transmit Data (Serial data output)
7
4
RTS
Request to send (acknowledge to modem that UART is ready to
D-Type-9
exchange data
8
5
CTS
Clear to send (i.e.; modem is ready to exchange data)
6
6
DSR
Data ready state (UART establishes a link)
5
7
SG
Signal ground
1
8
DCD
Data Carrier detect (This line is active when modem detects a carrier
4
20
DTR
Data Terminal Ready.
9
22
RI
Ring Indicator (Becomes active when modem detects ringing signal from PSTN
FIGURE 4.1 DB-9 PIN CONNECTOR
According to RS232 specifications, the logic ‘1’ and logic ‘0’ are called as ‘mark & ‘space’. The signal voltage levels are specified as ‘mark’ should be in the range of -3 to -15 volts and ‘space’ should be in the range of 3 to 15 volts. The modern low power consuming CMOS devices use different logic levels than the RS232 line specification. The logic levels of CMOS devices are in the range of 3.3v-5.5v for ‘1’ and -0.3v to 0.8v for ‘0’. Therefore when communicating with such CMOS/TTL devices, the logic levels need to be converted
RS232 INTERFACED TO MAX 232
2
T
1
O
U
1
T T
5
6 0
. 1
u
C0 . 5 1
u
0
u
f
. 1
3
1 3 f4 5
1 2
0
I NT I NT 1 1 2 2
V V 7 M . 1
I RN I RN
2 1
C C C C
f2 6
C
16
R R
1 0 .11 1 T T
XPD 3 C 4
V
C
8
A
1 2 O 9 U O U
1 2
T T
1 2
O O
T 1 4 7U T U T
2
3
2
P
3 R . 0X D 1
O
U
T
+ + -
+ u
C 1 1 u f
VCC
5 4 3 2 1
3
GND
9 8 7 6
U
X 3
15
J
f
Fig 4.2 RS232 INTERFACED TO MAX232
Rs232 is 9 pin db connector, only three pins of this are used ie 2, 3, 5 the transmit pin of rs232 is connected to rx pin of microcontroller
MAX232 INTERFACED TO MICROCONTROLLER
.
MAX232 is connected to the microcontroller as shown in the figure above
17,
18 pins are connected to the TX and RX pin i.e. transmit and receive pin of microcontroller
LIQUID CRYSTAL DISPLAY
INTRODUCTION: An LCD or a liquid crystal display consists of liquid crystals between electrodes. The arrangement consists of polarization filters which are aligned perpendicular to each other. This arrangement doesn’t allow any visible light if there was no liquid crystal between the filters. This arrangement is aligned in between transparent conductors. When sufficient voltage is applied to a certain pixel, the crystal at that pixel aligns such that no light passes through it. Therefore that particular pixel appears dark. If such an electric field is applied for a longer period, the alignment of the crystal change and the quality of LCD degrades. In a bigger LCD display, to provide voltage sources to each pixel, the rows and column lines are multiplexed.
PIN DESCRIPTION OF THE LCD:
TABLE: 4.1 PIN DESCRIPTION OF LCD
LCD INTERFACE WITH MICROCONTROLLER
Microcontroller P O R INTERFACING T P I N S
LCD TO MICROCONTROLLER
The LCD is generally interfaced in 8-bit mode or 4-bit mode. in this project LCD is connected in 4-bit mode the interface connections of LCD with microcontroller are as follows RS of LCD is connected to p0.0 of microcontroller EN of LCD is connected to p0.1 of microcontroller D4 of LCD is connected to p0.4 of microcontroller D5 of LCD is connected to p0.5 of microcontroller D6 of LCD is connected to p0.6 of microcontroller D7 of LCD is connected to p0.7 of microcontroller
In 8-bit mode, the complete ASCII code is sent at once along with the control signals. But in 4-bit mode, the data is divided into two parts, i.e. MSB & LSB, and are called upper nibble & lower nibble. The control signals are RS, R/W & E. RS is used to select the internal registers i.e. data register & command register. R/W is used to set the mode of LCD to read mode or write mode. E is used as chip select and is used to push the data internally to the corresponding registers. To transfer the data/command in 8-bit mode, the data is written to the 8-bit data bus after selecting the required register and setting the mode to write mode. The E signal pin is then given a high to low signal to transfer the data. To transfer the data/command in 4-bit mode, the higher nibble is first written to the MSB of the data port and the E is given a high to low signal. After a little
delay or when the LCD is not busy, the lower nibble is transferred in the same procedure.
LCD COMMANDS
Buzzer Piezo Electric buzzers are Solid state devices that produce an Audible signal when powered. _ They are basically made up of piezo crystal. _ The fundamental property of Piezo crystal states that when a voltage is applied to the crystal in a particular plane. It enters into oscillations. _ A simple oscillator circuit is used to make these signals audible.
Piezo electric buzzers operate right from 3V up to 24V DC. Similar to the LED drive, a transistor driver is used for driving the load. The other advantage with this scheme is that the drive voltage can be much higher than the operating voltage of the microcontroller. A protection diode is included in all inductive load circuits to prevent the back emf from damaging the driving transistor & subsequently the microcontroller.
BUZZER INTERFACE WITH MICROCONTROLLER
In this project buzzer is connected to P0.0 pin of the microcontroller.
Chapter 4 Software implementation 4.1 RIDE Please note that in this page RIDE will reference to RIDE6 software which supports 8051, XA and other derivates. For ARM, ST7 and STM8 family the software is RIDE7. RIDE is a fully featured Integrated Development Environment (IDE) that provides seamless integration and easy access to all the development tools. From editing to compiling, linking, debugging and back to the start, with a Simulator, ICE, Rom Monitor or other debugging tools, RIDE conveniently manages all aspects of the Embedded Systems development with a single user interface.
Fig: RIDE Multi-file Editor RIDE is based on a fast multi-document editor designed to meet the specific needs of programming. The various methods, menus, commands, and shortcuts are all fully compliant with the Microsoft® specifications for Windows 2000, XP and NT. Classic commands, such as string search and block action are integrated. Advanced features such as Matching Delimiter (parenthesis, brackets), Grep (multi-file search) and Indenter are integrated as well. The customizable color-highlighting feature is very useful to indicate specific syntactic elements as they appear in the source file: keywords, comments, identifiers, operators, and so on. The colorhighlighting feature is automatically keyed to the intrinsic file type (which means, it works differently for C and assembler).This permits the user to identify quickly and easily those parts of the code responsible for syntax errors. http://www.raisonance.com/products/info/RIDE.php - top Project Manager: The project manager creates links between the various files that includes a project and the tools necessary to create that project. A project is dedicated to a particular target: 8051, XA, or other microcontrollers. The linker manages object and library files, and output format conversion as necessary.
Fig Project Manager Tree-structured projects ease the management of the most complex applications (bank switching, flash, multi-processor, multi-module...). The ‘Project Make’ command directs the integrated "make" utility to build or rebuild the target programs for the current project. To avoid wasting time, each source file will be translated by its associated tool only if any of its dependencies are found to be out of date. Dependency analyses, even directly or indirectly included
files,
are
automatic.
Options can be defined as global (for all the files) or as local (for a specific node or file). Individual attributes can be set for any file in the project. Similarities between the different tools make migration from one processor family to another immediate and easy, permitting multiprocessor projects. http://www.raisonance.com/products/info/RIDE.php-top. The Message Window and the On-line Help: The message window displays all warning, error, and progress messages generated during the
processing
of
files
associated
with
each
project.
Clicking on an error string in the message window automatically positions the cursor at the point of that error in the source code window. The Online help system is context-sensitive and provides information on nearly all aspects of RIDE. A specific help file is supplied with each tool driven by the IDE ('C' Compiler,
Assembler, Linker, and RTOS). Online menu hints appear on the status line whenever you select a menu command.
Fig Message http://www.raisonance.com/products/info/RIDE.php-top. The Script Language: Most RIDE commands can be run from a script file. Scripts are written in a C-like language, and are interpreted at execution time. With the script language, most repetitive tasks can be done automatically thus speeding up operations and reducing the probability of errors. Scripts are very useful for Hardware Testing (board, emulator) and to initialize the system to a known status, but can also be conveniently used for other tasks such as creating very complex breakpoints or redirecting some output to a file to run a 'batch' debug session. http://www.raisonance.com/products/info/RIDE.php-top. Context Saving: When a project is closed, the whole associated context is saved (open file list, window size and position etc.). Settings associated with the debugger are also saves such as breakpoints, watches etc... http://www.raisonance.com/products/info/RIDE.php-top Integrated High-level Debug:
RIDE provides a fully integrated source-level debugging environment. All information necessary is derived from the translators used to accomplish each step of the process. This includes mundane aspects such as "path names", and source code specific information such as details of complex data types. With the simple click of a mouse button, the user can select among several powerful capabilities: simulate, monitor, or emulate. The fast smooth integration given by RIDE promotes a feeling of familiarity and ease of use, while providing a level of comfort and efficiency that reduces the most difficult and complex applications to tasks that are easily managed. This seamless progression of the "code-translate-link-debug-test" cycle is the result of perfect communication between the programming tools and the debugger. This is the heart of RIDE.
Fig : Debugger Integral Simulation: RIDE includes simulation engines for most 8051, and XA derivatives. The simulator/debugger is cleanly integrated into the presentation Windows. A wide range of 'views' can be selected to provide flexible direct examination of all memory spaces as well the all internal peripherals. The simulation engines perform detailed and faithful simulations (including IDLE or Power down modes), of all peripherals (including interrupt and watchdog events) present on the selected component. Advanced Features
RIDE provides a rich variety of 'views' into an application. These views or windows are associated with control commands like complex breakpoints or high level trace recording.
http://www.raisonance.com/products/info/RIDE.php - top 4.2 ISP 3.0 Introduction This ISP Programmer can be used either for in-system programming or as a stand-alone spi programmer for Atmel ISP programmable devices. The programming interface is compatibe to STK200 ISP programmer hardware so the users of STK200 can also use the software which can program both the 8051 and AVR series devices. Hardware The power to the interface is provided by the target system. The 74HCT541 IC isolates and buffers the parallel port signals. It is necessary to use the HCT type IC in order to make sure the programmer should also work with 3V type parallel port. The printer port buffer
interface
is
same as
shown
in
figure
1.For
the
u-
controllera40pinZIFsocketcanbe used. This programmer circuit can be use to program the 89S series devices and the AVR series device switches are pin compatible to 8051, like 90S8515. For other AVR series devices the user can make an adapter board for 20, 28 and 40 pin devices. The pin numbers shown in brackets correspond to PC parallel port connector.
Software The ISP-30a.zip file contains the main program and the i/o port driver. Place all files in the same folder. The main screen view of the program is shown in figure 3. Also
make
sure
do
not
program
the
RSTDISBL
fuse
in
ATmega8,
ATtiny26 and ATtiny2313 otherwise further spi programming is disable and you will need
a
parallel
programmer
to
enable
the
spi programming. For the fuses setting consult the datasheet of the respective device. For the auto hardware detection it is necessary to short pin 2 and 12 of DB25connector, otherwise the software uses the default parallel port i.e. LPT1. Following are the main features of this software,
Read and write the Intel Hex file.
Read signature, lock and fuse bits.
Clear and Fill memory buffer.
Verify with memory buffer.
Reload current Hex file.
Display buffer checksum.
Program selected lock bits & fuses.
Auto detection of hardware. Note: The
memory
buffer
contains
for the devices which
have
eeprom
both
the
code
memory.
The
data
and
eeprom
the
eeprom
memory
data
address
in buffer is started after he code memory, so it is necessary the hex file should contains the eeprom start address after the end of code memory last address i.e. for 90S2313 the start address for eeprom memory is 0x800.
The software
does
not
provide
the
erase
command
because
th
s function is performed automatically during device programming. If you are required to erase
the
controller, first use the clear
buffer command then program the controller, this will erase the controller and also set the AVR device fuses to default setting.
Fig Main screen of the program ISP-Pgm Ver 3.0a 4.3 EMBEDDED ‘C’ Ex: Hitec – c, Keil – c HI-TECH Software makes industrial-strength software development tools and C compilers that help software developers write compact, efficient embedded processor code. For over two decades HI-TECH Software has delivered the industry's most reliable embedded software development tools and compilers for writing efficient and compact code to run on the most popular embedded processors. Used by tens of thousands of customers including
General Motors, Whirlpool, Qualcomm, John Deere and many others, HI-TECH's reliable development tools and C compilers, combined with world-class support have helped serious embedded software programmers to create hundreds of breakthrough new solutions. Whichever embedded processor family you are targeting with your software, whether it is the ARM, PICC or 8051 series, HI-TECH tools and C compilers can help you write better code and bring it to market faster. HI-TECH PICC is a high-performance C compiler for the Microchip PIC micro 10/12/14/16/17 series of microcontrollers. HI-TECH PICC is an industrial-strength ANSI C compiler - not a subset implementation like some other PIC compilers. The PICC compiler implements full ISO/ANSI C, with the exception of recursion. All data types are supported including 24 and 32 bit IEEE standard floating point. HI-TECH PICC makes full use of specific PIC features and using an intelligent optimizer, can generate high-quality code easily rivaling hand-written assembler. Automatic handling of page and bank selection frees the programmer from the trivial details of assembler code. Embedded C Compiler ANSI C - full featured and portable. Reliable - mature, field-proven technology. Multiple C optimization levels. An optimizing assembler. Full linker, with overlaying of local variables to minimize RAM usage. Comprehensive C library with all source code provided. Includes support for 24-bit and 32-bit IEEE floating point and 32-bit long data types. Mixed C and assembler programming. Unlimited number of source files. Listings showing generated assembler.
Compatible - integrates into the MPLAB
IDE, MPLAB ICD and most 3rd-party
development tools. Runs on multiple platforms: Windows, Linux, UNIX, Mac OS X, and Solaris. Embedded Development Environment. PICC can be run entirely from the. This environment allows you to manage all of your PIC projects. You can compile, assemble and link your embedded application with a single step. Optionally, the compiler may be run directly from the command line, allowing you to compile, assemble and link using one command. This enables the compiler to be integrated into third party development environments, such as Microchip's MPLAB IDE.
