Download Java for embedded systems

Java for embedded systems
Felix G. Hamza-Lup
Outline
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Embedded systems characteristics
Application domains
Java characteristics
Java in embedded systems
Future trends
References
Embedded systems
• Real-Time systems
– Timing constrains play a critical role in their
design and implementation.
• Have dedicated functionality i.e. designed
strictly for a specific set of tasks
• Incorporate relatively low-speed
microprocessors and may have a limited
amount of memory.
Embedded systems - Inputs
• Random
• Short-lived external signals
• Processor must interrupt whatever else it is
doing to capture the data, or it will be lost
=> embedded programs are organized as a set of
individual, but cooperating threads of
execution.
Hardware for embedded applications
• Most embedded systems are housed within
a highly-constrained box.
– lack of space
– excessive vibration
=> embedded applications will be structured as a
small section of initialization code that starts
the programs from a ROM disk
Outline
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Embedded systems characteristics
Application domains
Java characteristics
Java in embedded systems
Future trends
References
Embedded systems – applic. domains
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Machine and process control
Medical instruments
Data acquisition
Network components: routers and switches
Less constraints
• Telephony: mobile phones, pagers
• PDAs
Outline
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Embedded systems characteristics
Application domains
Java characteristics
Java in embedded systems
Future trends
References
Characteristics
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Portability – platform independence
Software reuse – OO
Simplicity – easy to learn
Safety and security
- JavaTM Authentication and Authorization
Service (JAAS)
- JavaTM Cryptography Extension (JCE)
- Secure Socket Extension (JSSE)
Some key characteristics
• The key characteristics of Java that make it
attractive as a specification language for
embedded systems are:
– Built in multithreading and synchronization
– Lack of pointer arithmetic
– Automatic memory management
Outline
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Embedded systems characteristics
Application domains
Java characteristics
Java in embedded systems
Future trends
References
Technical challenges for embedded environment
Problems with “Desktop” Java
• Too big: JVM + JIT (just-in-time)
compiler+libraries  16 MB
• Too slow: 5 x slower than C code
• No notion of address: most often hardware
is accessed referring to a specific address
• Security, portability, dynamic behavior –
not needed in embedded systems
Problems with “Desktop” Java
• Java Garbage Collector - collect unused memory
• JCG – dangerous in embedded systems “stop-theworld effect”
• Memory allocation is not fast enough and not
predictable
Java embedded: alternatives …
• Special purpose JVM and core libraries
• JVM with JIT compiler
• Compiled JAVA (instead of interpreted)
Special purpose JVM and Frameworks
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Sun’s PersonalJava
Sun's EmbeddedJava
JIT – compiler
J2MicroEdition
JADE’s LEAP
PersonalJava
• Re-implements the full set of Java APIs defined by
the Java application environment
• Fits into smaller devices with more limited
memory configurations
EmbeddedJava - Goals
• Standardize software development for embedded
devices
• Integrate a compact EmbeddedJava application
environment directly into new devices
• Small adjustable memory footprint <=
Configurable APIs based on application.
EmbeddedJava - Sun's advanced tools streamline
• JavaFilter - builds a list of the specific fields and
methods used by the Java platform to run the Java
application
• JavaCodeCompact - optimizes the code by
removing unused parts of the platform.
• JavaDataCompact – for linking in auxiliary data
files such as HTML, image, and sound files.
Sun's EmbeddedJava Technology
EmbeddedJava Application Environment
JIT compiler
JIT vs. interpreted
Slow
JVM/JIT compiler & Products
• Dynamic compilation technique using a JIT
compiler but tradeoff between:
• performance
• memory consumption
• startup time
• KAFFE JIT- one order of magnitude better execution time
than Sun's JDK VM
• SuperCede VM - performs 58% and 91% faster then JDK
• Guava by Softway -better than Sun's JDK 1.0.2 VM
• Microsoft's JVM/JIT- in Internet Explorer ; PC Magazine,
“is the fastest JVM/JIT for the PC market.”
• KVM – Kilo Virtual Machine – small code size kernel
Compiled JAVA
• Java  native machine language
• Seems to be the current trend
• “Bye, bye”
– portability
– load new classes on-the-fly
• Best real-time behavior
J2MicroEdition
• A subset of the Java Standard Edition
• Notion of configuration
J2MicroEdition
• CDLC config.
– 160-512 kB of memory
– 16-32 bit processor
– network connectivity
• J2ME Wireless Toolkit
– debugging capabilities
– emulators
JADE
• Java Agent DEvelopment Framework
• Software framework fully implemented in
Java language
• A middle-ware that simplifies the
implementation of multi-agent systems
• Complies with the FIPA specifications
JADE’s LEAP on embedded systems
• Lightweight Extensible Agent Platform
• LEAP is an extension of JADE to enable it to run
on wireless devices and PDA's such as cell phones
and Palms
• 02/05/02 - LEAP 2.1 has been released
LEAP Architecture
LEAP agent communication
Target devices for LEAP
Outline
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Embedded systems characteristics
Application domains
Java characteristics
Java in embedded systems
Future trends
References
Trends
• Some constraints are relaxed: more
memory, cheaper CPUs …
• Real-time functionality - delivered by OS
not by JVM
• Tendency to link Java code with OS
proprietary code
• Real-time threads parallel to JAVA threads
• New distributed services
Trends - Real-time threads
References (1)
• http://java.sun.com/products/embeddedjava
• “What are the advantages of Java in embedded
systems?” F.Mueller, ECE 2002
• “Using Java in Embedded Systems” V.Ivanovic,
M. Mahar, Circuit Cellar, 1999.
• “Java on embedded systems” M.Gafen, NSI.com.
• “Personal Java – Application Environment
Specification v.1.1.2” 1999.
• Embedded systems conferences:
http://www.esconline.com/
References (2)
• “LEAP: a FIPA platform for mobile and handheld
devices” Frederico B., Agostino P.
• “Introduction to Java 2 Micro Edition”, Jeff
Brown, OCI (Object Computing Inc)
• JADE: http://sharon.cselt.it/projects/jade/
• LEAP: http://leap.crm-paris.com/
• FIPA: http://www.fipa.org/