T-106.5840 Seminar on Embedded Systems
eCos - An Embedded Configurable
Operating System
Shilei He
Department of computer science and engineering
Aalto University
shilei.he@aalto.fi
December 4th, 2014
Overview
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Introduction
Background
Layout and Components
Configuration Systems
Configuration tools
Comparison between eCos and other OS
Introduction
● eCos is a real-time operating system intended for
embedded applications.
● Open source, royalty-free
● Single process, multiple thread operating environment
● Single linked ELF binary image
● Highly configurable nature
● eCosCentric sells a closed , industrial strength
“eCosPro”
Background
● Initially developed by Cygnus Solutions on 1997.
● Primary goal was to bring a cost-effective, high-quality
embedded software solution to the marketplace
● Later bought by Red Hat in November 1999.
● In January 2004, Red Hat agreed to transfer its eCos
copyrights to the Free Software Foundation and finally
implemented in May 2008, changed name to
eCosCentric.
Layout of eCos
Example embedded software system showing layering
of eCos packages
Source: Anthony J. Massa , “Embedded Software
Development with eCos” . 2002-11-25
eCos Core Components
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Hardware Abstraction Layer (HAL)
Real-time Kernel
ISO C and math libraries
Device drivers
GNU debugger (GDB) support
Hardware Abstraction Layer
(HAL)
•The HAL is a software layer.
•It provides a platform independent API for
platform specific functionality.
•Enhances portability of code.
Real-time kernel
● The Kernel is the core component of eCos
system.
● Supports standard functionality:
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interrupt and exception handling
scheduling
thread synchronization
timers
device drivers
memory management
C and math libraries
Configuration system
● It is the key innovation technology of eCos.
● Select only the packages that are necessary through
configuration.
● Component architecture: standard eCos release,
commercial third party developers and open source
contributors
● Advantages of configuration system:
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customizable to precise application requirements
minimize the resource footprint / memory use
reduce time to market for embedded products
reduce costs
Configuration system (cont’d)
Software components control:
● At run time
o code size to be much larger
● At link time ( selective linking)
o unreferenced functions and data are removed
o But, only entire functions can be removed—an all-or-nothing approach
● Compile-time control/ source-level configuration
o configure at earliest stage
o best results in terms of code size
o applications are faster - not at run time
o the code is tailored for the application, creating an application-specific
RTOS
o reduce costs
Configuration system (cont’d)
● eCos uses compile-time control methods for its software
components, along with selective linking provided by the
GNU linker.
● This allows the application writer control over individual
lines of code in the packages.
● The control methods are implemented through C
Preprocessor
Configuration tools
● eCos uses Component Definition Language (CDL) to
describe the configuration of the system.
● Each system should have at least one CDL script file
● Two configurators:
o Configtool: GUI based
o ecosconfig: command line based
Configuration tools (cont’d)
#ifdef INCLUDE_FUNCTIONALITY
...
#else
...
#endif
Source-level configuration
Configtool
Source: Invoking the eCos Configuration Tool,
Web source:
http://ecos.sourceware.org/docs-latest/user-guide/
config-tool-invoking.html
Comparison
Comparison between eCos and Realtime Linux, MicroC/OS-II on
memory requirement, context switch
and interrupt latency
Minimum
memory
requirement
eCos
(Bytes)
RTLinux
(Bytes)
MicroC/OS-II
(Bytes)
10K
4M
2K
Table 1: Minimum memory requirement
Source:
1. Amir Hossein Payberah, “Embedded OS
Benchmarking”
2. Fei Li, “Comparison of several open-source realtime operating system”, October 2013.
Context
Switch (us)
Interrupt
Latency
(us)
Testing
environment
eCos
15.84
19.2
MPC860A3
(33MHz)
RTLinux
Idle system
33.1
13.5
PowerPC 604
(300MHz)
RTLinux
Loaded
system
193.9
196.8
PowerPC 604
(300MHz)
MicroC/OS-II
29.7~34.2
78.8
Intel80186
(33MHz)
Table 2: Kernel performance comparison
Conclusion
● eCos is a free open source real-time operating system
intended for embedded applications.
● High configurability
● eCos uses compile-time control methods.
● Feature and Advantage
o customizable to precise application requirements
o minimize the resource footprint / memory use
Question?
Reference
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Red Hat, “Red Hat to contribute copyrights held in the eCos code based to the Free Software
Foundation”, in Press. 2004-01-13.
“The GNUPro Toolkit”, 2007, Red Hat, Inc. Retrieved 2014-11-25
Jonathan Larmour, “Smaller, faster, open source, free: the eCos RTOS”, 2006
eCos website, Web source: http://ecos.sourceware.org/, accessed on 2014-11-15.
Pentek, Inc, Real-Time Embedded Configurable Operating System, Retrieved 2014-11-25
“eCosCentric annouces eCosPro Developer’s Kit ”(Press release). OSNews. 2003-09-02.
Retrieved 2014-11-25
Anthony J. Massa , “Embedded Software Development with eCos” . 2002-11-25
Invoking the eCos Configuration Tool, Web source:
http://ecos.sourceware.org/docs-latest/user-guide/config-tool-invoking.html, accessed on
2014-11-16
Arnaud Hubaux , Yingfei Xiong, Krzysztof Czarnecki, “A User Survey of Configuration
Challenges in Linux and eCos”, 2012
Fei Li, “Comparison of several open-source real-time operating system”, October 2013.
Amir Hossein Payberah, “Embedded OS Benchmarking”, Retrieved 2014-11-25