RealTimeAndEmbeddedSystems_Part5 mathhoang vietnam_hoangminhnguyen

8/8/2019 RealTimeAndEmbeddedSystems_Part5 mathhoang vietnam_hoangminhnguyen

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Real-Time and EmbeddedSystems

Nam HoDr. Anh-Vu Dinh-Duc


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8/20/2010 Embedded Systems Course: Development of Embedded Systems - 2010 2

Module Outline

Introduction to Real-Time SystemsReal-Time Task SchedulingReal-Time Operating Systems (RTOS)Measuring Execution Time and Real-Time Performance

Development of Embedded SystemsOur Research Results in EmbeddedSystems


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Development of EmbeddedSystems

Development ProcessConsists of cycles of editing-testing-debuggingProcessor and hardware part oncechosen remains fixed, the applicationsoftware codes have to be perfected by anumber of runs and tests


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Cross-Platform Development


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Cross-Platform Development

Software for an embedded system is developed onone platform but runs on anotherThe host system is the system on which the

embedded software is developedThe target system is the embedded system underdevelopmentA set of connections might be available betweenthe host and the target system

JTAGBDMSerial PortEthernet


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Host System

Offering essential development tools(toolchain)

EditorCross compiler, assemblerLinkerSource-level debugger

Produces executable binary image that will runon target system

At PC, workstation, laptop


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Toolchain for BuildingEmbedded Software

Target system

Building Process


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GNU Toolchain for Developmentof Embedded Systems

Free SoftwareGNU make : Automation tool for compilation andbuildGNU Compiler Collection (GCC): Suite of compilersfor several programming languagesGNU Binutils : Suite of tools including linker,assembler and other tools

GNU Debugger (GDB): Code debugging toolC Library : uLibc, gLibcSupporting x86, ARM, MIPS, PowerPC, SuperH
http://en.wikipedia.org/wiki/Make_%28software%29http://en.wikipedia.org/wiki/GNU_Binutilshttp://en.wikipedia.org/wiki/GNU_Debuggerhttp://en.wikipedia.org/wiki/GNU_Debuggerhttp://en.wikipedia.org/wiki/GNU_Binutilshttp://en.wikipedia.org/wiki/Make_%28software%29


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Integrated DevelopmentEnvironments (IDE)

An IDE is referred as a programming environmentthat has been packaged as an application programTypically consisting of

Code editorSimulatorToolchainGraphical user interface (GUI) builder

Companies design the IDE to develop embedded

systems on specified microcontrollersIncluding BSPStartup CodeDevice Driver


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KEIL IDE


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Eclipse IDE for C/C++ Developerwith GNU Toolchain for ARM


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Target System

Actual hardware for the embedded system under developmentEmbedded developers are required to understand the target system

How to store the program image on the target embedded systemHow to develop and debug the system iteratively


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Target System & Final System

In target system, it might be repeated downloadingof the codes during the development phaseReprogramming the EEPROM or the flash memoryeach time the code changes due to bugs or codeaddition is time consumingDevelopers transfer the image directly into thetarget system's RAM memory over serial/networkconnection or through JTAG/BDM interfaceFinal system (product) may employs ROM in placeof flash, EEPROM or EPROM in embedded system


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Compiling & Linking

Executableimage

Compiling/Linking

How ?

How ?


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Compiling

Output from compilation is an object fileAn object file contains

File size, binary code and data size, andsource file name from which it was created

Machine-architecture-specific binaryinstructions and dataSymbol table and the symbol relocationtableDebug information, which the debuggeruses

Two common object file formatsCOFF (common object file format)ELF (extended linker format)


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Compiling The ELF Format

.o .elf


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Compiling Object File

Object file contains headerthat describe the rest of

the sectionsBlocks regrouped

Code blocks in text sectionInitialized global variables indata sectionUninitialized globalvariables in bss section


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Linking

Linker combines several object (.o) files into asingle executable file (.elf)


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Linking Linker

Merges text, data, and bss sectionsUnresolved symbol matching

Referred variable is undeclared in one file but isdeclared in another fileLinker will replace with reference to the actualvariable

Normally, the address in the executableimage is the absolute address (physicaladdress)


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Linking Linker Script

Set of linker directives that controls how thelinker combines the sections and allocatesthe segments into the target systemTwo of the more common directivessupported by most linkers are MEMORYand SECTION

The MEMORY directive is used to describe thetarget systems memory map The SECTION specifies how the sections are tobe merged and at what location they are to beplaced


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MEMORY {ROM: origin = 0x0000h, length = 0x0020hFLASH: origin = 0x0040h, length = 0x1000hRAM: origin = 0x1000h, length = 0x10000h

}

SECTION {.text :{

my_section *(.text)}loader : > FLASHGROUP ALIGN (4) :{

.text,

.data : {}

.bss : {}} >RAM

}


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Downloading the ExecutableImage to the Target System

Programming the entire image into theEEPROM or flash memory

Downloading the image over either aserial (typically RS-232) or networkconnection

Downloading the image through eithera JTAG or BDM interface


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The boot image prepares the system to execute the loader (ex. Testing RAM)The loader prepares the serial or network connection to receive the imagefrom host

Setting the baud rateInitiating the transfer protocol (FTP, TFTP)

The monitor (boot image + loader) has a set of commands allowing thedeveloper to (via serial/network connection)

download the imageread from and write to system memory locationsset and clear different types of breakpointssingle-step instructionsreset the system

Target debug agent functions much like the monitorThe target agent gives the host debugger enough information to provide visualsource-level debug capabilitySometimes a RTOS vendor offers a host-based debugger (target server)

Debugging solutionsICEJTAGBDM


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VxWork runs on the x86 target


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Debugging the ExecutableImage on the Target System

How to debug the loader/ monitor ? (Board bring-upprocess)Using an Emulator

A circuit for emulating target systemDebug startup code and programs running from ROM


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In-Circuit Emulator (ICE)Replaces microprocessor in target systemExpensive


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On-Chip Debugging (OCD)Built-in microprocessor debugging

BDM and JTAG solutions


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JTAG (Joint Test ActionGroup)Founded by electronics

manufacturers to develop anew and cost-effective testsolutionThe IEEE1149.1 standard


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BDM (Background Debug Mode)Introduced by Motorola and found onits processor chips


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Target Boot Scenarios

After embedded processors are poweredon, they fetch and execute at the reset vector

The reset vector is usually a jump instructioninto another part of the memory spacewhere the real initialization code is foundAfter that the startup initialization code can

begin at the flash memory addressInitializes the hardware (only the necessarydevices)Contains the target image loader


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Target Boot Scenarios

ldr pc, [pc, #64] ; 00000040

Embeddedprocessors are built-

in a small boot code


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Executing from ROM usingRAM for data


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Executing from RAM afterimage transfer from ROM


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Executing from RAM afterimage transfer from Host


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Target System SoftwareInitialization Sequence

Task objectsSemaphore objectsMessage-queue objectsTimer servicesInterrupt servicesMemory-management servicesCreating necessary stacks

Setting up execution handlersInitializing interrupt handlersInitializing bus interfaces, such asPCI, and USBInitializing board peripherals such asserial, LAN, and SCSI.


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Reference

Qing Li and Carolyn Yao, Real-Time Concepts for Embedded Systems,

CMP Books, 2003Raj Kamal, Embedded Systems - Architecture, Programming and

Design , McGraw-Hill Pulisher, 2008

Documents

RealTimeAndEmbeddedSystems_Part5 mathhoang vietnam_hoangminhnguyen