Sun SPOT

Sun SPOT is a technology of networks of sensors without wire conceived by the American company Sun Microsystems Inc. SPOT means “technology for small programmable objects” (Small Programmable Object Technology). The characteristic of SPOT is to provide a software and material platform homogeneous to develop applications with the language of programming Java. The material part rests on standards or spread architectures, such as the interface wireless networking IEEE 802.15.4 and the processors ARM.

Material specifications

A SPOT is the assembly of a chart with the main frame, a chart gathering the various sensors or a station of basic emission, a base to accommodate the batteries, and a hull to contain the whole.

Principal elements of the chart of the processor

Processor ARM920T given rhythm to 180 MHz, 32 bit, 512Ko of random access memory, 4Mo of memory Flash
Interface radio " Zigbee" (based on the standard IEEE 802.15.4, 2.4 GHz)
integrated Antenna
Interface USB

Principal elements of the chart of the sensors

three-dimensional Accelerometer 2G/6G
thermal Sensor
Sensor of light
8 LED, each one being able to post 3 colors different
6 analogical entries
2 switches on return
5 pins from inputs/outputs and 4 high pins of exit for current

Food and Consumption

Batteries refillable lithium-ion, 3.7V, 750 mAh (of simple batteries R6 type can be used)
Consommation of 30 uA in mode of sleep prolonged (“deep sleep mode”)
automatic Gestion of the batteries by the software layer

Software specifications

The SPOT have a virtual Machine Java which deals with the functions of operating system. The technology developed for SPOT names the project Squawk, so originating in Sun Microsystems Inc.

The reasons advanced for this technological choice are that the existing implementations of the virtual machines Java are too expensive for so small machines, and the specifications of Java ME (in particular CLDC) could be optimized more. Squawk is the result of this analysis.

Virtual machine Squawk

Entièrement compatible with the specifications Java ME CLDC 1.1
Intégrations of the essential functionalities of an operating system
direct Exécution starting from the memory Flash
the pilots of peripherals can be entirely written in Java
Energy management

Development tools

Any environment of Java development can be used
the SPOT connected to computers via port USB behave like basic stations to manage and deploy applications.

Safety

The aspect safety is relatively traditional for a Java platform, with certain optimizations. Each application must be signed before being able to be deployed and carried out. The SPOT check that the applications are actually signed before starting them.

Into the level cryptography, Sun integrated versions improved of the algorithms RSA and ECC, in order to allow their execution on the SPOT (these algorithms are in general too gourmant for very small computers).

Other information

Positioning

Sun SPOT is one of last technologies available for the networks of sensors. The platforms appeared before are in particular technologies originating in the University of California, Berkeley, with the operating system TinyOS and the “motes” such as the products of Xbow or Moteiv.

The principal difference between the approaches of Sun SPOT and TinyOS are the respective use of Java and NesC (a componentielle alternative of C more suitable). The advantages of the use of Java are an increased homogeneity due to the portability of the language, and certain more developed aspects of safety. The advantages of the use of NesC are a control moreover low level of the resources and the existence of many extensions supported by an international community.

Availability

The first SPOT have been available for a few months (April 2007 in the United States). The kits of introduction contain 3 Spots, including two with sensors, and one as a basic station, of the development tools software and a cable USB. The software continuation is compatible with Windows XP, Mac OS X 10.4 and the majority of the Linux distributions.

The dates of availability out of the United States were not announced yet.

External bonds

Official site Sun SPOT

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