software platform devoted to serve education, research and development in the fields of ambient .... TinyOS [10] is not real-time and has severe limitations, but it is a good option for .... [4] The ember company website: http://www.ember.com/.
A MODULAR PLATFORM FOR EMBEDDED INFORMATION TECHNOLOGY Csaba Tóth László Kádár
Gyula Simon Tamás Dabóczi Balázs Scherer Gábor Samu Zoltán Benesóczky Gábor Péceli Department of Measurement and Information Systems, Budapest University of Technology and Economics, Hungary and Embedded Information Technology Research Group, Hungarian Academy of Sciences E-mail: {toth,simon}@mit.bme.hu Abstract. This paper presents the design considerations of a modular hardwaresoftware platform devoted to serve education, research and development in the fields of ambient intelligence, ubiquitous/pervasive computing, and networked embedded systems. The primary goal of this new platform is to support Embedded Information Systems Engineering education at the Budapest University of Technology and Economics, one of the few attempts world-wide to cover and integrate the wide range of knowledge required in the field of embedded systems.
1 Introduction The recent technological advances in the field of embedded systems open completely new vistas for the educators and researchers of electrical and computer engineering communities. As a relatively prompt reaction, a new major in Embedded Information Systems Engineering (EISE) was introduced for electrical engineering students at the Budapest University of Technology and Economics (Budapest, Hungary) in February 2000. The major is one of the first attempts in the world to respond to the urgent need of the industry to provide well-educated engineers in Embedded Information Systems (EIS), integrating the wide range of knowledge required by EIS curricula [1]. Its core part (88 ECTS credits) includes 10 mandatory courses in hardware, software, and systems engineering, project laboratory courses, and a master’s thesis. To maintain balance between theory and hands-on experience and to force practical problem solving, in 2004 a new hardware platform called mitmót was introduced for the EISE students, accompanying them during their studies, and serving as target device for several home projects of different major-related subjects. To motivate the students, the devices are capable of solving interesting problems arising in the fields of ambient intelligence, ubiquitous/pervasive computing, and networked embedded systems. Every student can take home his basic mitmót set together with some simple development tools, and ‘play’ with his own ‘mini-laboratory’ using his personal computer. These communicating mini-laboratories together with a well-equipped central laboratory form the mitmót distributed laboratory system.
2 Motivations and challenges Students selecting the EISE major in their 6th semester already have strong background in the basic electrical engineering subjects (math, physics, signals and systems, control theory, programming, etc.), and in the major they study further aspects of signal processing, computing theory, real-time and distributed systems, optimization, evaluation, system architecture and engineering. To help integration of knowledge and the development of practical skills, at each stage of their studies students need hands-on experience, and thus suitable hardware/software platforms. Naturally, educational excellence requires the usage of tools, which are in the current mainstream of the industry and research, and can be used to implement and study state of the art applications and techniques. It is advantageous if the platform is the same at different stages (learning phases can be shortened), but it also must be rich enough to help the development of skills in different areas. The platform should reflect the typical nature of the EIS field, and must be interesting enough to motivate students. The designed platform must be robust and easily usable; must have a well-defined and robust interface (both mechanically and electrically); and a simple and inexpensive debugging tool so that it can be given to the students for home usage. Sensor networks provide an interesting challenge, since in addition to programming and interfacing individual devices the students can work with multiple communicating units, offering interesting application areas and technical problems to solve. During their studies, based on the proposed tools and technologies students learn microprocessor programming, sensor interfacing, digital signal processing, wireless sensor networking, and the basics of complex system design. In the second half of the program, where teamwork is essential, students solve practical sensor networking problems. With this extension of the EIS program the students exercise almost all aspects of embedded systems engineering, and by the end of their studies, they will have real engineering skills and experience.
3 Design considerations of the modular mitmót1 system Among the several sensor-networking platforms available on the market [2], [4], probably the most successful for educational purposes is the Berkeley mote system, which consists of a standard ‘motherboard’ including the processor and the radio, and a wide variety of replaceable sensor boards [2]. Although this is an excellent platform for both educational and prototyping purposes, the proposed mitmót system offers even higher flexibility and more didactical structure, including a higher level of decomposition, multiple processor platforms, several communication modules, and sensor boards. In many embedded systems 8-bit microcontrollers are used, but market trends show the spread of 32-bit processors. For educational purposes in the proposed system multiple processor platforms were chosen, featuring 8-bit and 32-bit controllers. In embedded systems several communication platforms are used, e.g. Ethernet, powerline, and wireless communication. ZigBee, developed for low-speed communication of inexpensive sensors will probably be an important wireless standard in the future [3]. 1
The ‘mitmót’ is a Hunglish pun constructed from the word ‘mit’ (the Hungarian abbreviation of the Department of Measurement and Information Systems, also meaning what) and the Hungarian spelling of the English word ‘mote’, referring to very small, but intelligent devices in the fields of ambient intelligence, pervasive computing, and sensor networks.
Although low-level programming of embedded systems is an important skill for EIS engineers, more demanding applications require the utilization of (real-time) operating systems. TinyOS [10] is not real-time and has severe limitations, but it is a good option for many applications due to its very small footprint. Real-time operating systems (free for educational purposes) are also available, such as µC/OS [6], [7] and eCos [8], [9]. Power awareness is an important feature of real sensor networks and embedded systems in general, thus power saving modes must be supported by both hardware and software. The packaging and mechanical properties of the mitmót system are of crucial importance, since the devices are mainly dedicated for educational purposes. The connectors must be especially robust and durable, also providing sufficiently stable mechanical connection between the stacked boards.
4 The mitmót system The mitmót system is dedicated to education and prototyping; thus the main functionalities are implemented on separate modules. The mitmót modules enable the creation of various devices from the standard processor-, communication-, sensor-, and actuator modules. The complete list of standard mitmót modules can be found in Table 1. The set of mitmót modules is continuously extended and the students are strongly encouraged to design and build new modules for their projects if the standard set is not suitable for their purposes. All devices are built upon one of the microcontroller modules, performing the computation tasks and the coordination of other modules. For didactical reasons two processor boards were designed: the 8-bit board is built around the Atmel AVR, while the 32-bit board (see Figure 1) features a Philips processor with ARM7 core. Multiple communication modules can provide information exchange in the sensor network and also towards higher-level external devices (e.g. a wireless and an Ethernet module). The wireless module uses the 802.15.4/ZigBee compliant CC2420 radio chip. The sensor and actuator modules allow interfacing with the physical environment. The basic I/O module provides a simple man-machine interface, while the acoustic and DC motor drive modules allow creation of more sophisticated mobile applications. The power is supplied primarily by three AA-size batteries, but the board accepts other sources in a wide voltage range. All components are designed to have low power consumption and can be switched off when not in use to spare energy. All the mitmót modules are stackable. Mechanical and electrical connections are provided by two robust 28-pin connectors. The primary operating system is the µC/OS [6], which has small footprint, is easily configurable and easy to understand. For the 32-bit board the more powerful eCos [8] is also used. The students’ mini-laboratories are accompanied by shareware development tools for both processor platforms [7], [9], while the central mitmót laboratory located at the University provides additional proficient development and debugging tools. Table 1. Standard mitmót modules 32-bit Philips LPC2106 processor board ARM7 core, 128 KB flash, 64 KB SRAM, 54 MIPS µC/OS, eCOS real-time operating systems Radio module (CC2420) 2.4 GHz, spread spectrum, max 250 kbps, ZigBee Basic I/O module LEDs, display, pushbuttons, switches, thermometer Acoustic module analog I/O, microphone, loudspeaker
8-bit ATMEL AVR processor board 128 KB flash, 4 KB SRAM, 8 MIPS µC/OS real-time operating system Ethernet module Ethernet MAC, 10 Mbit/s Power line module communication through the power line, max 1 kbps DC motor driver module 2 DC motor drivers, 2 rotation sensors
Figure 1. The 32-bit microcontroller module and the stacked mitmót modules
5 Concluding remarks The Embedded Information Systems Engineering (EISE) major offered at the Budapest University of Technology and Economics is extended by a set of tools accompanying the students through their last 4-5 semesters. The mitmót system, primarily designed for educational purposes, provides high motivation for the students who can take their own minilaboratories home, encouraging them to experiment with the system even in their spare time, thus providing deeper understanding and practical experience in the field of embedded information technology. The mitmót system is highly modular, providing a wide range of functional units, including various processor, communication, and sensor/actuator boards. Easy expandability was a primary goal during the design. The mitmót system is an excellent platform for research projects, too, providing fast prototyping and testing possibilities for ideas in the fields of ambient intelligence, pervasive computing and sensor networks. The modular design offers high flexibility, and a wide variety of possible devices can quickly and easily be created from the available set of modules.
References [1] Guidelines for a Graduate Curriculum on Embedded Software and Systems (http://www.artist-embedded.org ). [2] Hill, J., and Culler, D., “Mica: A Wireless Platform for Deeply Embedded Networks,” IEEE Micro, Vol. 22(6), Nov/Dec 2002, pp. 12-24. [3] The ZigBee Alliance website: http://www.zigbee.org/ [4] The ember company website: http://www.ember.com/ [5] Chipcon radio frequency integrated circuits (http://www.chipcon.com). [6] Jean J. Labrosse: “µC/OS-II, The Real-Time Kernel.” Second Edition. CMP Books, 2002. [7] The µC/OS home page: http://www.ucos-ii.com [8] Anthony J. Massa: “Embedded Software Development with eCos.” Bruce Perens’ Open Source Series. Prentice Hall, 2002. [9] The eCos home page: http://sources.redhat.com/ecos/ [10] The TinyOS website: http://www.tinyos.net/
