An Entire Concept of Embedded systems

EMBEDDED
SYSTEMS
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Agenda
Embedded System Basics – PART 1
Introduction to Embedded systems
Embedded Processors & their Architectures
Serial communication
RTOS Concepts
Videos of Embedded applications
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Embedded Programming in C- PART 2
Embedded Software Development Process and Tools
Embedded programming Demo for PIC Microcontroller & simulation using Proteus & MPLAB IDE
How to write a program
How to handle the datasheets of the processors
Embedded programming Demo for MSP430 by using Code Composer Studio
How to write a program
How to handle the datasheets of the processors
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System Definition
A way of working, organizing or performing one or many tasks according to a fixed set of rules, program or plan.
Also an arrangement in which all units assemble and work together according to a program or plan.
Examples:
Time display system – A watch
 Automatic cloth washing system- A washing machine
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System Examples
It is an automatic clothes washing system Parts: Status display panel, Switches & Dials, Motor, Power supply & control unit, Inner water level sensor and solenoid valve.
Process:
1.Wash by spinning
2.Rinse
3.Drying
4.Wash over by blinking
5.Each step display the process stage
6.In case interruption, execute only the remaining
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Embedded Systems- Definition
“An embedded system is a system that has software embedded into computer-hardware, which makes a system dedicated for an application(s) or specific part of an application or product or part of a larger system.”
It is any device that includes a programmable computer but is not itself intended to be a general purpose computer.”
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Embedded Systems- Architecture
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Microprocessors
CPU for Computers
No RAM, ROM, I/O on CPU chip itself
Example：Intel’s x86, Motorola’s 680x0
CPU
General- Purpose Micro- processor
RAM
ROM
I/O Port
Timer
Serial COM Port
Data Bus
Address Bus
General-Purpose Microprocessor System
Many chips on mother’s board
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•A smaller computer
•On-chip RAM, ROM, I/O ports...
•Example：Motorola’s 6811, Intel’s 8051, Zilog’s Z8 and PIC 16X
A single chip
RAM
ROM
I/O Port
Timer
Serial COM Port
Microcontroller
CPU
Microcontrollers
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Processor Architectures
1-Von Neumann Architecture
Single memory & single bus for transferring the data into & out of the CPU.
Multiplication of two numbers require atleast 3 clk cycles
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2-Harvard Architecture
 Separate memory for data & program with separate buses for each
Both program instructions & data can be fetched at the same time
Operational speed is higher than Von Neumann
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3-Super Harvard Architecture (DSP Processors)
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 DSP Algorithms spend their most of the time in loops. So instruction Cache is added
 Processing of many “high” frequency signals in real time
 Multiply–Accumulate operation
 Fixed point/ floating point, Matrix operations, convolution , correlation, parallelism etc.
eg:C5000, C6000 single core processor families

DSP Pipeline Architecture
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C6000 fetch eight 32 bit instructions per clock cycles

Mechanism in Microcontrollers
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Difference between DSP & μC
DSPs often don't have a flash program memory. They need the software to be 'loaded' into them. Whereas, microcontrollers have a non power off erasable program memory inside, some with EPROM store capabilities.
DSPs are much faster for integer mathematics operations, whereas many microcontrollers do not have the hardware.
DSPs are much faster for floating point operations. In microcontrollers, this has to be done in software.
DSPs are oriented to be an input/output device with 'fast calculating machine'. Microcontrollers are a multi-feature device with several ways of interfacing with the world, however none are the fastest.
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DSPs are not designed to be a 'robust' device. They need a well designed board to work properly. Microcontrollers can work on a Test Board.
DSPs are a fast calculator microprocessor, that is very effective for computing calculations and moving data, whereas, microcontrollers are a more flexible device with more features.
Eg: 1) Image, audio & video processing by DSP
2)Data-transmission & control signals by Microcontroller
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Texas Instruments (DSP+ARM processor)
Davinci- (video streaming applications )
Multicore processors
 OMAP application processors (Image processing)
Analog Devices
Black-fin Processor (DSP+ARM)
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Digital Signal Controllers (Combined Processor Architectures)

How the PC Starts
Microcontroller searches its first instruction to execute
BIOS in Flash chip provides the Initial instructions to the μc
BIOS does several sequences:
1. Check the CMOS Setup for custom settings
CMOS setup present in Nonvolatile RAM (NVRAM) or CMOS RAM
CMOS RAM & RTC integrated as a Southbridge Chipset, which is powered by CMOS battery (CMOS RAM-64 to 512 bytes capacity)
CMOS setup consists of sys time/date, Chipsets status, memory management
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2. Load the interrupt handlers and device drivers
3. Initialize registers and power management
4. Perform the power-on self-test (POST)
5. Display system settings
6. Determine which devices are bootable
7. Initiate the bootstrap sequence – the order to Boot OS
Cold boot – restart PC with the power being off
Warm boot or normal boot- restart PC when the power is ON
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HARD DISK
MOTHER BOARD

VARIOUS MICROCONTROLLERS
INTEL
8031,8032,8051,8052,8751,8752, Pentium etc
PIC
8-bit PIC16, PIC18, 16-bit DSPIC33 / PIC24, PIC16C7x
Motorola
MC68HC11
ARM – ARM7, ARM9, ARM 11
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Types of Processors
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EMBEDDED PROCESSOR
Special microprocessors & microcontrollers often called, Embedded processors.
An embedded processor is used when fast processing fast context-switching & atomic ALU operations are needed.
Examples : ARM 7, INTEL i960, AMD 29050.
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DIGITAL SIGNAL PROCESSOR
DSP as a GPP is a single chip VLSI unit.
It includes the computational capabilities of microprocessor and multiply & accumulate units (MAC).
DSP has large number of applications such as image processing, audio, video & telecommunication processing systems.
It is used when signal processing functions are to be processed fast.
Examples : TMS320Cxx, SHARC, Motorola 5600xx
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APPLICATION SPECIFIC SYSTEM PROCESSOR (ASSP)
ASSP is dedicated to specific tasks and provides a faster solution.
An ASSP is used as an additional processing unit for running the application in place of using embedded software.
Examples : IIM7100, W3100A
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APPLICATIONS
Household appliances:
Microwave ovens, Television, DVD
Players & Recorders
Audio players
Integrated systems in aircrafts and
missiles
Cellular telephones
Electric and Electronic Motor controllers
Engine controllers in automobiles
Calculators
 Medical equipments etc...
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Automotive embedded systems
Today’s high-end automobile may have 100 microprocessors
4-bit microcontroller checks seat belt
microcontrollers run dashboard devices
16/32-bit microprocessor controls engine
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SERIAL COMMUNICATION
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SERIAL PORT:
one bit can communicate & the bits transmitted at periodic intervals generated by a clock.
Short and long distance communication.
PARALLEL PORT:
Multiple bits can communicate over a set of parallel lines at any given instance.
Communication within the same board.
Short distance communication.
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Serial communication
Mainly divided into
Synchronous- Data is received or transmitted at constant time intervals with uniform phase differences. Eg: audio inputs, frames sent over a LAN
Asynchronous- Data is received or transmitted at variable time intervals. Eg: keypad communication, Modem.
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Synchronous
Asynchronous
Constant time intervals
Random time intervals
No Handshaking between Tx & Rx
Handshaking between Tx & Rx
Clock is known to the receiver explicitly
Clock is known to the receiver implicitly
Eg: SPI, SCI, SI and SDIO
Eg: RS232, UART, HDLC etc
DIFFERENCE
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Synchronous Transmission
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Asynchronous Transmission
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What is the difference between RS232 and UART?
RS232 is a specification for serial communications between a DCE and DTE it defines electrical characteristics, the 25-way 'D' connector and the various functions of the various signal lines.
A UART is a Universal Asynchronous Receiver and Transmitter - it is an electronic circuit which handles communication over an asynchronous serial interface - very often an RS232 interface.
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UART Frame format
1
0
1bit time= 1/baud rate
10 transition
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RS232
Interfacing signal standard
Follows asynchronous UART protocol
Point to point interface
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UART circuit within microcontroller
RS232
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SERIAL COMMUNICATION PROTOCOLS
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SPI- Synchronous Peripheral Interface
-Defined by Motorola on the MC68HCxx line of microcontrollers
-Full duplex
-It supports 1) full master mode 2) slave mode(with general address call) - Addressing each device is not needed
•-If SS pin set as 1- Master
-If SS pin set as 0- Slave
-It is called as 3 wire communication
-Allows 8 bit to transmit & receive
-Generally faster than I2C, capable of several Mbps
-Bus Arbitration logic is needed
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 A master sends a clock signal, and upon each clock pulse it shifts one bit out to the slave, and one bit in, coming from the slave.
Master PIC
Slave PIC
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Using separate chip selects Daisy chaining
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BUS ARBITRATION

Applications of SPI
Like I2C, used in EEPROM, Flash, and real time clocks
Better suited for “data streams”, i.e. ADC converters
Full duplex capability, i.e. communication between a codec and digital signal processor
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I2C (Inter Integrated Circuit)
Developed by Philips Semiconductor for TV sets in the 1980’s
2-wire serial bus – Serial data (SDA) and Serial clock (SCL)
Half-duplex, synchronous
I2c supports 1) master mode
2)slave mode
3)multi master mode
 Addressing is needed (eg: In PIC- MSSP Address Register )
No chip select or arbitration logic required
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I2C
1. Master sends start condition (S) and controls the clock signal
2. Master sends a unique 7-bit slave device address
3. Master sends read/write bit (R/W) – 0 - slave receive, 1 - slave transmit
4. Wait for/Send an acknowledge bit (A).
5. Send/Receive the data byte (8 bits) (DATA).
6. Expect/Send acknowledge bit (A).
7. Send the STOP bit (P).
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I2C Data Transfer
Data Transfer from master to slave
Data transfer from slave to master
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Example

Applications
Used as a control interface to signal processing devices that have separate data interfaces, e.g. RF tuners, video decoders and encoders, and audio processors.
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CAN
CAN is a serial bus system, which was originally developed for automotive applications in 1980 by BOSCH
Data link layer protocol internationally standard as ISO 11898-1
Referred as network of independent controllers
CAN provides 2 Communication Services:
Sending of a message- data frame transmission
Requesting of a message- remote transmission request
Message based protocol not an address based protocol
Bidirectional and the data rate is 1 Mbps
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12
6
7Bits(all zeros)
1 1 1
If RTR sets as 1- packet is a data to the RX
If RTR sets as 0- packet is a request for the data from the RX
CAN DATA FRAME FORMAT
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3.75v
2.5v
1.25
2.5v
1
0
1
CAN HIGH
CAN LOW
Idle
Transmitting Bits
Idle
Recessive Dominant Recessive
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USB (Universal Serial Bus)
Bus between host system & number of interconnected peripheral devices
Addressable bus system
Hot swapping or hot plugging or plug & play- no Interruption, no reboot, auto configuration.
Bus powered
Star topology
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Star topology

3 standards are :
USB 1.1-1.5 Mbps to 12 Mbps, support up to 127 devices
USB2.0-1.5, 12 and 480 megabits per second data transfer
USB 3.0-Super Speed >4.8 Gbits/sec
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Up stream
Down stream
PIN Diagram

USB ROOT HUB CONTROLLER or HOST INTERFACE CONTROLLER
USB STICK
MASTER
SLAVE
MEMORY CONTROLLER
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When the Host powers up, Enumeration process starts (host address 0x00)
-polls each of the Slave devices
-assigns unique address (7bit address code)
-finds each device Speed and type of data transfer
-device drivers are loaded for auto configuration
-virtual pipes are established for data communication
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(Unidirectional)

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USB can support four data transfer types or transfer mode: 1. Control 2. Isochronous eg: keyboard, mouse 3. Bulk eg: printer 4. Interrupt eg: memory stick

Secure Digital (or SD) is a non-volatile FLASH memory card format for use in portable devices, such as mobile phones, digital cameras, GPS navigation devices, and tablet computers.
Flash memory is an electronic non-volatile computer storage device that can be electrically erased and reprogrammed.
Programmable for communication in SPI mode or 1bit SD mode or 4bit SD
Secure Digital Card(SDIO)
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Multi media cards
2 NAND CHIPS AND ONE SD CONTROLLER
Secure Digital Card(SDIO)
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Memory Model
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When func calls, temporary variables are pushed.
When func exits, variables are popped
Dynamic memory allocation, Malloc,realloc,free
Objects and
Program memory
Data memory

Stack : store temporary variables created by funcs
Fast access
Managed automatically by CPU
Local variables only
Limited stack size. (stack overflow will occur)
Grows downwards- going to reach its limit
Heap : memory allocation can be done by using malloc, realloc & free (dynamic memory allocation)
Slow access
Managed by the programmer
Variables can be accessed globally
No limit on memory
Grows upwards- its limit increases continuously
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Process and Threads
A process is an instance of a computer program that is being executed. It contains the program code and its current activity
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PROCESS
THREADS
Instance of a computer program being executed
Subsets of a process
Independent resources & memory
Shared resources & memory
Context switching is slow
Context switching is fast
Independent
Depends on their own process

Process Concept
Process – a program in execution process execution must progress in sequential fashion
A process includes:
program counter
stack
data section
Task is a similar one to process. But the term TASK is often used in RTOS.
Task – a embedded program in execution
But in some RTOS, the term PROCESS is also used
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Process State
As a process executes, it changes state
new: Create & memory allotted
ready: The process is waiting to run while the high priority tasks are running
running: executing with allotted resources. Some times it preempts by another priority task
Waiting(blocked): The process is waiting for some event to occur
terminated: The process has finished execution & memory gets de-allotted.
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Diagram of Process State
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(Blocked)

Process Control Block (PCB)
Information associated with each process
Process state
Program counter
CPU registers
CPU scheduling information
Memory-management information
Accounting information
I/O status information
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CPU Switch From Process to Process
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Process Scheduling Queues
Job queue – set of all processes in the system
Ready queue – set of all processes residing in main memory, ready and waiting to execute
Device queues – set of processes waiting for an I/O device
Processes migrate among the various queues
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Ready Queue And Various I/O Device Queues
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Migration of ‘A’ From Disk to Register
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Interrupts is a mechanism for alleviating the delay caused by this uncertainty and for maximizing system performance.
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Transferring Data Between the CPU and I/O Device
What is Interrupt Mechanism ?

Transferring Data Between the CPU and I/O Device
•Polling
•Wait states
•Interrupts
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Polling
One method used in small system to alleviate the problem of I/O devices with variable delays.
Repeatedly checking its ports
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CPU
I/0 device
Request Again
Device ready signal
Fails
Request
Data transfer

wait states
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CPU
I/0 device
am waiting
Device ready signal
Please wait
Request
Device ready signal
Data transfer

Disadvantages of Polling & wait states
The CPU does not perform any useful work while waiting for the I/O device to become ready to transfer data. To make use of this wasted CPU time, interrupts are developed.
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Interrupts
Instead of polling the device or entering a wait state, the CPU continuously executing its instructions & performing useful work.
When the device is ready to transfer data, it sends an interrupts request to the CPU; this is done via a dedicated signal on the control bus.
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CPU
I/0 device
Interrupt ACK signal
Interrupt Request
Data transfer

1. Normal program execution
2. Interrupt occurs
3. Processor state saved
4. Interrupt routine runs
5. Interrupt routine terminates
6. Processor state restored
7. Normal program execution resumes
Handling an Interrupt
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Context switching
Context switching

Shared data problem
•Arises when an interrupt service routine and the task code share the data or between two tasks that share the data.
•In order to solve the problem, we need to make the shared data “atomic”
•A part of the program is said to be “atomic” if it cannot be interrupted by anything
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Semaphores
Semaphores: Introduced by Dijkstra in 1960s
Semaphore is a variable or a signal event
Provides the synchronization mechanism
Eg: open-close, up-down, pend-post, lock-unlock
Synchronization mechanism is required at the entry and exit of critical section to ensure exclusive use. This mechanism is semaphore.
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Semaphores have two purposes
Mutex: Ensure threads don’t access critical section at same time
Scheduling constraints: Ensure threads execute in specific order
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Semaphores

Real time Semaphores
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Railways
Airways
Navy

Mutual Exclusion (Mutex)
Mutex is a program or object that is created, when we start the process.
Any task needs the resource must use the Mutex to lock the resource from other task while it is using the resource.
If the Mutex is already locked, other tasks are queued.
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Critical section
In concurrent programming, a critical section is a piece of code that accesses a shared resource that must not be concurrently accessed by more than one thread of execution.
Semaphore taken critical section semaphore release
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Conditions for Implementing the Critical Section
Disable the interrupts, when try to enter into the CS
Avoid system calls that can cause a context switch while inside the CS.
Whatever may be, any kind of code must not disturb the CS, until the original thread leaves its CS.
This approach can be improved by using semaphores.
Eg: Printer can only be accessed by one process at a time
But other processes are free to gain the control of CPU & execute other code or CS that are protected by different semaphores.
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Deadlock Characterization
Deadlock can arise if four conditions hold simultaneously.
Mutual exclusion: only one process at a time can use a resource.
Hold and wait: a process holding at least one resource is waiting to acquire additional resources held by other processes.
No preemption: a resource can be released only voluntarily by the process holding it, after that process has completed its task.
Circular wait: there exists a set {P0, P1, …, P0} of waiting processes such that P0 is waiting for a resource that is held by P1, P1 is waiting for a resource that is held by P2, …, Pn–1 is waiting for a resource that is held by Pn, and P0 is waiting for a resource that is held by P0.
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Pre-emption
The act of temporarily interrupting a task being carried out by a computer system without requiring its cooperation.
Preemptive scheduler consists of high priority tasks which has the power to preempt or interrupt any process.
But kernel functions cannot be preempted
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Embedded Software's:
IDE- Integrated Development Environment
Compiler The compiler turns source code into machine code packaged in object files. (HI-tech compiler, CCS etc)
Cross compilerA cross-compiler produces object files that will then be linked for the target instead of the computer running the compiler
A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the compiler is running.( eg: GCC for linux)
DebuggerA special program used to find errors (bugs) in other programs. A debugger allows a programmer to stop a program at any point and examine and change the values of variables.
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The Simulator tries to duplicate the behaviour of the device. The Emulator tries to duplicate the inner workings of the device.(mimicry)
Emulation is the replacement of a real world device with an model at a well defined interface for the purposes of allowing controlled responses from the emulated real world device.
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Introduction to MSP430
The MSP430 can be used for low powered embedded devices.
The electric current drawn in idle mode can be less than 1 μA.
The top CPU speed is 25 MHz. It can be throttled back for lower power consumption.
Six different low-power modes, which can disable unneeded clocks and CPU.
Capable of wake-up times below 1 microsecond, allowing the microcontroller to stay in sleep mode longer, minimizing its average current consumption.
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PIN DIAGRAM OF MSP430G2553
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Digital IO Control:
Digital I/O is configured by user software
– Input Register PxIN
– Output Register PxOUT
– Direction Register PxDIR
– Pullup/Pulldown Resistor Enable Register PxREN
– Function Select Registers PxSEL and PxSEL2
• Most likely will not need to use these
– Each pin has interrupt capabilities
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Input Register PxIN
Each bit in each PxIN register reflects the value of the input signal at the corresponding I/O pin when the pin is configured as I/O function.
Bit = 0: The input is low
Bit = 1: The input is high
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Output Registers PxOUT
Each bit in each PxOUT register is the value to be output on the corresponding I/O pin when the pin is configured as I/O function, output direction, and the pullup/down resistor is disabled.
Bit = 0: The output is low
Bit = 1: The output is high
If the pin's pullup/pulldown resistor is enabled, the corresponding bit in the PxOUT register selects pullup or pulldown.
Bit = 0: The pin is pulled down
Bit = 1: The pin is pulled up
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Direction Registers PxDIR
Each bit in each PxDIR register selects the direction of the corresponding I/O pin, regardless of the selected function for the pin. PxDIR bits for I/O pins that are selected for other functions must be set as required by the other function.
Bit = 0: The port pin is switched to input direction
Bit = 1: The port pin is switched to output direction
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Pullup/Pulldown Resistor Enable Registers PxREN
Each bit in each PxREN register enables or disables the pullup/pulldown resistor of the corresponding I/O pin. The corresponding bit in the PxOUT register selects if the pin is pulled up or pulled down.
Bit = 0: Pullup/pulldown resistor disabled
Bit = 1: Pullup/pulldown resistor enabled
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Function Select Registers PxSEL and PxSEL2
Port pins are often multiplexed with other peripheral module functions. See the device-specific data sheet to determine pin functions. Each PxSEL and PxSEL2 bit is used to select the pin function - I/O port or peripheral module function.
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How to enable the pins or bits
Each pin in port can also acts as a register.
If the port 1 has 8 pins (p1.0 to p1.7)
To enable the pins: just set 0 or 1
For example set P1.1 & P1.6 and form the hexadecimal code
4 2
Write as 0x42
P1.7
P1.6
P1.5
P1.4
P1.3
P1.2
P1.1
P1.0
0
1
0
0
0
0
1
0
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Low power modes
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#define LPM0_bits (CPUOFF)
#define LPM1_bits (SCG0+CPUOFF)
#define LPM2_bits (SCG1+CPUOFF)
#define LPM3_bits (SCG1+SCG0+CPUOFF)
#define LPM4_bits (SCG1+SCG0+OSCOFF+CPUOFF)
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#define LPM0 _bis_SR_register(LPM0_bits) /* Enter Low Power Mode 0 */
#define LPM0_EXIT _bic_SR_register_on_exit(LPM0_bits) /* Exit Low Power Mode 0 */
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Led toggling:
#include <msp430g2553.h>
unsigned int i;
void main(void)
{
 WDTCTL=WDTPW + WDTHOLD;// watch dog timer disabled
 P1DIR |= 0X41; // here itself P1OUT = 0100 0001 //led on the pin will glow
 while(1)
 {
 P1OUT ^= 0X41; //0100 0001 Exor 0100 0001= 0000 0000// led will off for the given delay
 for(i=0;i<50000;i++);
 }
}
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Analog to digital module
The ADC10 module is a high-performance 10-bit analog-to-digital converter.
Refer the data sheet page no: 558
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The USCI module is used for serial data communication. The USCI module supports synchronous communication protocols such as SPI (3 or 4 pin) and I2C, an asynchronous communication protocols such as UART, enhanced UART with automatic baudrate detection (LIN), and IrDA. Not all packages support the USCI functionality.
USCI_A0 provides support for SPI (3 or 4 pin), UART, enhanced UART, and IrDA.
USCI_B0 provides support for SPI (3 or 4 pin) and I2C.
Universal Serial Communications Interface (USCI)
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UART Steps:
1. The I/O pins have to be selected for the UART function
2. A clock with a certain frequency must be sourced to the UART module
3. Enable UART TX or RX or Both
4. Select the byte format as 7- or 8-bit data with odd, even, or non-parity
5. Set the baud generator correctly so as to get a correct baud rate from the clock sourced
6. Enable the module
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synchronous
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16X2 LCD PIN OUT
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EMBEDDED COMPANIES
Intel
Texas Instruments
 Freescale
 Philips
 Samsung
 LG Electronics
 Tata Elxsi/Sasken
 Ittiam Systems
 Infosys/TCS
 HCL Technologies/Wipro
 Analog Devices
 Mphasis/BFL
 Symphony
 Sonata Software
 Mistral/eInfochips
Dexcel Designs
Robosoft/Yindusoft
Qualcomm
Etc…………….
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Thank you
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An Entire Concept of Embedded systems

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An Entire Concept of Embedded systems