Real-time Systems Lab, Computer Science and Engineering, ASU CSE 438/598 Embedded Systems...

Real-time Systems Lab, Computer Science and Engineering, ASU

CSE 438/598 Embedded Systems Programming – Fall 2014

Computer Science & Engineering DepartmentArizona State University

Tempe, AZ 85287

Dr. Yann-Hang [email protected](480) 727-7507


Course Syllabus (1)

Course Goals: Understand the design issues of embedded software and gain an

in-depth knowledge of development and execution environment. Understand the functions and the internal structure of device

interfaces, drivers, and real-time operating systems. Acquire the skill to develop multi-threaded embedded software in

target environment, including good quality and coding style for embedded programming, and testing and debugging approaches.

Develop feasible task scheduling and carry out system performance and task schedulability analyses.

Pre-requisites: Assembly language and computer organization (CSE230),

microprocessor interfaces (CSE 325), and experience of C programming language

Knowledge of operating systems and computer architecture

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Course Syllabus (2)

Introduction: characteristics of embedded applications (2 lecture) Embedded processor architecture: processor architecture,

exceptions and interrupts, and system memory map. (4 lectures) Device interface and programming approaches: interconnection

architecture, serial buses, and device controllers (3 lectures) Device driver: software structure of device driver, Linux loadable

kernel module, blocking and non-blocking IO, top-half and bottom-half ISR. (6 lectures)

Embedded software and thread programming: task model and specification, periodic and aperiodic tasks, imprecise computation, overrun management, signaling, setjmp and longjmp. (5 lectures)

Basic RTOS and services for multiple threads or tasks, mutexes, semaphores and software timers. (4 lectures)

Scheduling algorithms and analysis: cyclic, rate-monotonic, and EDF,scheduling,, priority inheritance, and analysis. (4 lectures)

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Course Syllabus (3)

Office hours –2:30pm-4:00pm, Tuesday and Thursday Evaluation

1st midterm exam* (20%) (in class, 75 minutes, Tuesday, Oct. 21) 2nd midterm exam* (30%) (12:10pm-2:00pm, Thursday, Dec. 11) 5 Lab assignments (40%) Class attendance and participation, discussion board participation,

and video sharing (10%) All exams are closed book and closed notes. The lab assignments must be done individually. There will be a

20% deduction per day for late submission. Request a regrade of exam or assignments within a week from the

date that the grade is returned. Plagiarism and other anti-intellectual behavior will be dealt with

severely.

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Lab Setup

Intel Galileo board and additional periperals

Prepare your own micro SD card (and adapter) for booting

Preferred development software Linux, Eclipse, command lines, GUN tools

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Real-time Embedded Systems

Embedded system the software and hardware component that is an

essential part of another system Real-time system

provide well-timed

computation deadlines, jitters,

periodicity temporal dependency

Plantsensor actuator

Control-rawcomputation

A/D

A/DD/AReference

input

Controller

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Embedded Systems -- Examples

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Emerging Embedded Systems

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Embedded Systems

They are everywhere What are they?

Hardware (chips) + Software (programs)

for specific applications

CPU(micro-

processor)

I/O

I/O

I/O

I/O

Timer

memory

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SW Development for RT ES

To write the control software for a smart washer initialize read keypad or control knob read sensors take an action

System current state state transition diagram external triggers via

polling or ISR If there are multiple triggers and

external conditions – single or multiple control loops

initialization

external trigger?

Take actions

Change system state

ISR: to set/clearevents

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SW Development for RT ES

In the example of smart washer Never-ending in a single control loop Single execution threat and one address space Event triggering and state transitions Small memory footprint

What are missing: no concurrency (real-world events occur in parallel) no explicit timing control (let’s add a timer) difficult to develop and maintain large embedded systems –

verifiable, reusable, and maintainable

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RT ES vs. General Software

Multi-tasking for concurrent events Machine dependence and portability Software abstraction, modular design

information hiding, OO, separate compilation, reusable a sorting procedure -- function, input, output specification

Control timing predictable actions in response to external stimuli deadline (absolute or relative), and jitter

Resource constraints and sharing CPU time, stack, memory, and bandwidth

Scheduling

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Embedded System Development

Need a real-time (embedded) operating system (RTOS) or run on bare metal ?

Need a development and test environment ? Use the host to edit, compile, and build application programs At the target, use tools to load, execute, debug, and monitor

(performance and timing)

Development Host (gnu tool chain + Eclipse)

Target Peripherals + Plant Model

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Development Environment of Linux

Host PC workstation

gcc cross-compiler

Linux

Eclipse IDEGDB Server

Target board

Board

support package

Applications

Linux or Windows

GDB debugger

Command line or IDE (Eclipse, Kdevelop)

Linux and GNU tools

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HelloWorld Example

/* Hello World program */#include <stdio.h>#include <time.h>

int main(void) { int i; time_t curTime;

for (i=0; i<10; i++) { curTime = time(NULL);

printf("Hello, world. The current time is: %s", ctime (&curTime));sleep(i);

}}

CC = i586-poky-linux-gccall: HelloWorld.c

$(CC) -o HelloWorld.o HelloWorld.c

scp HelloWorld.o [email protected]:/home/root/labs/

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Compiler, linker, and loader In ELF: executable, relocatable, shared library, and core

information for relocation, symbol, debugging linker resolves symbol reference

Link script or link command file assigns absolute memory addresses (program area, static data, bss,

stack, vector table, etc.) Startup code to disable interrupts, initialize stack, data, zero

uninitialized data area, and call main().

From Source to Executable

cc

asm

ldlinker loader debugger

linker script executable

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Debugger

Observability, real-time analysis, and run control At host: GUI, source code, symbol table, type

information, line number Communication to the target

serial port, Ethernet, USB, etc. read/write memory and registers control processor execution (single step, breakpoint, watchpoint,

etc.) At target:

debugging stub (software): at breakpoint, replace the instruction with breakpoint inst. or invalid instruction to trigger exception

BDM (JTAG interface): hardware breakpoint, trace buffer, flash programming

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Trends of RT Embedded Systems Applications

Wide-spreading, distributed, connected, and heterogeneous Mission and safety critical High-end consumer products

cell phone, HDTV, home network, PDA, GPS, appliances Quality of the products

portable/reusable, reliable/dependable, interoperable, predictable (schedulable), and secured

Software extensive A new S-class Mercedes-Benz

over 20 million lines of code nearly as many ECUs as the new Airbus A380 (excluding the plane's

in-flight entertainment system).

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Software Complexity

Software in Smartphones = apps + android + Linux Linux kernel:

Android:

Language Code Comment Blank PercentageC 15,213,100 3,277,849 2,919,083 94.5%Assembly 474,013 99,107 77,428 2.9%C++ 238,689 107,606 49,138 1.7%XML 85,470 520 7,079 0.4%Make 39,575 11,901 10,859 0.3%Totals 16,086,836 3,504,100 3,070,580

Language Code Comment Blank PercentageC 4,790,691 1,541,950 1,021,643 42.5%C++ 2,922,477 896,141 624,506 25.7%Java 1,530,288 770,935 321,929 15.2%HTML 955,041 51,284 220,949 7.1%XML 524,855 75,396 34,453 3.7%Totals 11,431,145 3,546,030 2,333,226

(Analyses from http://www.ohloh.net/)

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Reliable Embedded Software

Bill Gate: in FOCUS, 1995, “There are no significant bugs in our released

software that any significant number of users want fixed.” Numerous recalls for software bugs have occurred in

automobiles Smart cars: transition from mechanical to electronic control Toyota Prius: a software problem that caused the gas engines

to stall at highway speeds Volvo’s recall of S60 sedans due to software problems with the

fuel pumps. Jaguar: a software bug prevented cruise control from being

turned off

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Toyota’s ETCS-i and Unintended Acceleration

Electronic Throttle Control System, Intelligent (ETCS-i) a closed loop throttle control function. learning algorithms to recalibrate sensor inputs. NASA “found no electronic flaws .. to create UA incidents”

But, in Appendix A compiler warnings extensive use of global

variables, indirection,

name overloading, and

code duplication dead code, warnings from

static analyzer violations of coding standards (NASA Engi. and Safety Center Technical

Assessment Report)

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Advances in general-purpose computers PCs are powerful, cheap, and versatile Information processing is ubiquitous

Thanks for the growth in productivity The design gaps

Building Embedded Systems

Process technology

Hardware design

Software design

2x/18 months

1.6x/18 months

2x/5 years

0 3 6 9 12 151

10

100

1,000

HW gap

SW gap

(International Technology Roadmap for Semiconductors, 2011)

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Embedded Software

Characteristics Concurrent, time dependent, and device/environment dependent

Embedded software development 80% programs in embedded system is with C/C++ and 15% in

assembly the same thing that has been done more than 30 years (Ada?)

Software complexities inherent and cannot be eliminated, i.e. algorithm, concurrency, etc. accidental (due to technology or methods used), i.e. memory leaks

What can we do? abstraction (e.g. high-level languages, modeling) automation (e.g. compiler)

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Design for Performance and Predictability

A system vs. a piece of code Computer science is about abstraction, but resource is

needed to run any piece of code a switch statement a branch table if (unlikely(!timer)) return -EINVAL;

Benchmarking and profiling data measurement and interpretation resource usage and hot spots

A good understanding on what hardware and software are doing space and time tradeoff compiler optimization time and resource requirement

abstract

physical

model

data structure

algorithm

O(n), O(n2)…

object

operating system

compiler library

CPUmemory

instruction set

IO & Bus

time/cyclesignal

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Embedded Coding Practices

Informal rules to improve the quality of software applications simplify their maintenance

MISRA-C:2012 143 rules checkable using static code analysis makes development as predictable as possible, across projects or

pieces of code, without errors of interpretation Holzmann’s “Power of Ten” and JPL coding standard Examples:

check return value of non-void functions name convention – dump_data_to_file() no compilation warnings no errors or warnings resulting from static code analyzers

(Image credit: Wikidave)

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http://www.flickr.com/photos/wikidave/7118464049/sizes/c/





Embedded Software Analysis Tools (1)

Static and dynamic tools to show the correctness and performance of software systems

VDC Research (2012-02-01). "Automated Defect Prevention for Embedded Software Quality"

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Embedded Software Analysis Tools (2)

A simple example:

Static analysis tools Lint, PolySpace, CODAN of Eclipse null pointer de-reference, use after free, array indexing errors,

stack and heap overrun, etc.

IDE, debug and trace tools Performance and profiling tools:

gprof, perf, Valgrind profiler,

Intel Amplifier Memory and thread tools:

Valgrinde memcheck and DRD, Intel Inspector

in single core in dual core

vs.

(Wind River Workbench’s System Viewer)

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