Intro to Embedded OS, RTOS and Communication Protocols

Team Emertxe
Introduction to Embedded
Concepts
Communication Protocols
RTOS

Introduction to Embedded
Contents
●
Concepts
●
Communication Protocols
●
RTOS
●
A Case Study

Embedded Systems
Concepts
●
What do you understand as Embedded System?
●
How different they are from a General Purpose System (GPS)?

Embedded Systems
Definition
“Any Hardware System which is intended to do a
specific task
can be called as an Embedded System”

Embedded Systems
Requirements
●
Reliability
●
Cost-effectiveness
●
Low Power Consumption
●
Efficient Usage of Processing Power
●
Efficient Usage of Memory
●
Appropriate Execution Time

Embedded Systems
Trends
●
Processors
●
Memory
●
Operating Systems
●
Programming Languages
●
Development Tools

Embedded Systems
Common Design Metrics
●
Time to Prototype
●
Power
●
Performance & Correctness
●
Size
●
NRE
●
Maintainability & Flexibility
●
Safety
●
Unit Cost
●
Time to Market

Embedded Systems
Development Environment - Example

Embedded Systems
Development Tools
●
Compilers and its friends
●
Debuggers
●
Simulators
●
Emulators
●
Programmers or Flashers

Embedded Systems
Communication Protocols - Serial
●
A bit getting transmitted at a given instance of time
●
Must follow one of the below mode
– Simplex
– Half duplex
– Duplex
●
The type of transfer could be
– Synchronous
– Asynchronous
●
Sync entity has be decided

Communication Protocols - I2
C

Embedded Systems
Communication Protocols - I2
C
●
Two Line Interface
– Synchronous
– Half duplex
– Multi master and multi slaves
●
Software Addressable
●
Multi Master with CD
●
Serial, 8 bit Oriented, Bidirectional with 4 Modes

Embedded Systems
Communication Protocols – I2
C - Example
LCD Driver EEPROM RTC
Temperature
Sensor
ADC
Microcontroller
A
Microcontroller
B
DATA
CLOCK

Embedded Systems
C – Wired AND
SCL
SDA
VDD
SCLN1
OUT
SCL
IN
DATA1
OUT
DATA
IN
SCLN2
OUT
SCL
IN
DATA2
OUT
DATA
IN
DEVICE1 DEVICE2

Embedded Systems
Comm... Pro... – I2
C – A complete transfer
SCL
SDA
ADDRESS R/W ACK
1 - 7 8 9
DATA ACK
1 - 8 9
DATA ACK
1 - 8 9
S P

Embedded Systems
C – Multi Master
●
Data arbitration
●
Clock Synchronization

Embedded Systems
Communication Protocols - SPI
●
Synchronous
●
Full Duplex
●
Master / Slave

Embedded Systems
Communication Protocols – SPI - Interface Lines
●
SCLK
●
MOSI
●
MISO
●
nSS

Embedded Systems
Communication Protocols – SPI – HW Interfaces
SCLK
MOSI
MISO
SS1
SCLK
MOSI
MISO
SS
Master Slave 1
Single Master and Single Slave

Embedded Systems
SCLK
MOSI
MISO
SS1
SCLK
MOSI
MISO
SS
Master Slave 1
Single Master and Three Slaves
SCLK
MOSI
MISO
SS
Slave 2
SCLK
MOSI
MISO
SS
Slave 3
SS2
SS2

Embedded Systems
SCLK
MOSI
MISO
SS1
SCLK
MOSI
MISO
SS
Master Slave 1
Single Master and Three Daisy Chained Slaves
SCLK
MOSI
MISO
SS
Slave 2
SCLK
MOSI
MISO
SS
Slave 3

Embedded Systems
RTOS – What?
●
Real Time Operating System
●
An scheduling implementation which that guarantees a
certain capability within a specified time constraint

Embedded Systems
RTOS – Why?
●
Most operating systems appear to allow multiple
programs to execute at the same time, known as
multitasking
●
Scheduler gives an illusion of simultaneous execution by
rapidly switching between each program even though its
running in a single core!!
●
So the GPOS scheduler will try and ensure the system
remains responsive to its user
●
But an embedded system which generally designed to
have single purpose, should efficiently handle all its
events fairly, and would require an better scheduler
which could handle its resources

Embedded Systems
RTOS – How it achieve? - Architectural Difference
Mionolithic Kernel
Based Operating System
Micro Kernel
Based Operating System
VFS
IPC, File Systems
Scheduler, Virtual Memory
Device Drivers, Dispatcher... Basic IPC, Virtual Memory, Scheduling
VFS
Application
Device Drivers, Dispatcher...
HardwareHardware
User
Mode
Kernel
Mode
Application
Unix
Server
Device
Driver
File
Server
System Call

Embedded Systems
RTOS – When?
●
RTOS is not a required component of all real-time
application in embedded systems. An embedded system
in a simple electronic semi automatic washing machine
does not require RTOS.
●
But, embedded systems are becoming more complex
hardware-wise with every generation
●
With increase in its complexity, application programs
running on the embedded system platforms will become
increasingly complex to be managed as they strive to
meet the system response requirement

Embedded Systems
RTOS – Classifications
●
Hard real-time: degree of tolerance for missed deadlines
is extremely small or zero. A missed deadline has
catastrophic results for the system
●
Firm real-time: missing a deadline might result in an
unacceptable quality reduction
●
Soft real-time: deadlines may be missed and can be
recovered from. Reduction in system quality is
acceptable

Embedded Systems
RTOS – Features
●
Multitasking and Pre-emptibility
●
Task Priority
●
Reliable and Sufficient Inter Task Communication
Mechanism
●
Priority Inheritance
●
Predefined Short Latencies
●
Control of Memory Management

Embedded Systems
RTOS – Building Blocks
Task Management
Scheduler
Synchronization
IPC
Semaphore
Memory Management
Interrupt Services
Device I/O Management
BSP

Intro to Embedded OS, RTOS and Communication Protocols

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Intro to Embedded OS, RTOS and Communication Protocols