WISENET
ABSTRACT
WISENET is a wireless sensor network that monitors the environmental conditions such as light, temperature, and humidity. This network is comprised of nodes called "motes" that form an ad-hoc network to transmit this data to a computer that function as a server. The server stores the data in a database where it can later be retrieved and analyzed via a web-based interface. The network works successfully with an implementation of one sensor mote.
The technological drive for smaller devices using less power with greater functionality has created new potential applications in the sensor and data acquisition sectors. Low-power microcontrollers with RF transceivers and various digital and analog sensors allow a wireless, battery-operated network of sensor modules ("motes") to acquire a wide range of data. The TinyOS is a real-time operating system to address the priorities of such a sensor network using low power, hard real-time constraints, and robust communications.
1. INTRODUCTION
The last few years have seen the emergence of numerous new wireless technologies have reached the market recently. While the general trend is to offer higher and higher data rates, there are many existing and new applications that do not require such a high bandwidth, but would strongly benefit from a wireless communication link. Examples of such applications are wireless sensor networks. In this perspective, the Microelectronics Division has launched a project called WISENET. Its main objective is to develop a low-power wireless ad-hoc network made of many distributed microsensors that are energetically autonomous and able to communicate amongst them and with the external world. WISENET will enable the monitoring and the control of physical and environmental parameters for a variety of applications. For example, WISENET will monitor security and safety in the future homes and offices
The first goal of WISENET is to create a new hardware platform to take advantage of newer microcontrollers with greater functionality and more features. This involves selecting the hardware, designing the motes, and porting TinyOS. Once the platform is completed and TinyOS was ported to it, the next stage is to use this platform to create a small-scale system of wireless networked sensors.
2. SYSTEM DESCRIPTION
There are two primary subsystems (Data Analysis and Data Acquisition) comprised of three major components (Client, Server, Sensor Mote Network).
2.1) Primary Subsystems:
There are two top-level subsystems -
Data Analysis Data Acquisition.
2.1.1)Data Analysis:
This subsystem is software-only (relative to WISENET). It relied on existing Internet and web (HTTP) infrastructure to provide communications between the Client and Server components The focus of this subsystem was to selectively present the collected environmental data to the end user in a graphical manner.
2.1.2)Data Acquisition:
The purpose of this subsystem is to collect and store environmental data for later processing by the Data Analysis subsystem. This is a mix of both PC & embedded system software, as well as embedded system hardware. It is composed of both the Server and Sensor Mote Network components.
3. SYSTEM COMPONENTS
System components are Client, Server, and Sensor Mote Network.
CLIENTSERVERSENSOR MOTE NETWORK
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Internet
HTTP
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TCP/IP
HTTP Server
RS232 SERIAL
Gateway
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980MHZ RF Comm.
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Wise DB
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Web Program
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Web Browser
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SQL
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Data Analysis Subsystem
Data Acquisition Subsystem
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Figure 1: WISENET System Block Diagram
3.1) Client:
The Client component is necessary but external to the development of WISENET. That is, any computer with a web browser and Internet access could be a Client. It served only as a user interface to the Data Analysis subsystem.
3.2) Server:
The Server is a critical component as the link between the Data Acquisition and Data Analysis subsystems On the Data Analysis side, an web (HTTP) server hosting a web application. When a page request came in, the web server executes the web application, which retrieved data from the database, processes it, and returns a web page that the web server transmitted to the Client. For the Data Acquisition system there is a daemon (WiseDB) running to facilitate communication with the Sensor Mote Network.
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WEB page Requests
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Inputs & Outputs
Data packets
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Requested WEB page
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Figure 3: Server Components Inputs/Outputs
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This daemon is responsible for collecting raw data packets from the Sensor Mote Network. These packets are then processed to convert the raw data into meaningful environmental data. This processed data is then inserted into the database. Thus the database is the link between the Data Analysis and Data Acquisition subsystems. The Server also had the potential to send commands to the Sensor Mote Network (via the gateway mote), although this functionality was not explored in WISENET.
It should be noted that since the SQL database connections can be made via TCP/IP, only the web server and web-program (see figure 4) needed to be located on the same physical machine. The web server, the database, and WiseDB could all be on different physical machmes connected via a LAN or the Internet. This allows a flexible Server component implementation that is useful during WISENET development.
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WEB Program
TinyOS Daemon WISEDB
SE>SOR NETWORK
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(GATEWAY MOTE)
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▲TCP/IP / SQL / TCP/IP
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Figure 4: Server Component Block Diagram
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3.3) SENSOR MOTES
SERVER PC pCOMMANDS
SENSOR MOTES
SENSOR NETWORK
(GATEWAY MOTE)
ONLY / INPUTS
„ SERVER PC / OUTPUTS
DATA PACKETS
Figur
The primary focus of WISENET is the development of the Sensor Mote Network component. It is the component responsible for collecting and transmitting raw environmental data to the Server. There is also the potential for the motes to receive commands from the Server, although that functionality may not be implemented in WISENET. Uses for this feature would mclude server-based synchronization and wireless network reprogramrning.
t SENSOR NETWORK DATA PACKETS
SENSOR NETWORK
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DATA PACKETS
4ENVIRONMENT HUMIDITY, LIGHT etc.,
nits/Outputs
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This component consists of two parts. The first is the sensor mote. The primary purpose of the sensor mote is to collect and transmit raw environmental data. When not doing this, it went into a low-power idle mode to conserve energy. Another aspect of the sensor motes involved ad-hoc networking and may be for multi-hop routing;
The gateway mote is the second part of the Sensor Mote Network. Its purpose is to serve as the liaison between the Server and the Sensor Mote Network and deliver all the data packets to WiseDB In theory both standard and gateway motes could be implemented on the same hardware PCB and with the same software. For WISENET, however, resource and time constraints necessitated the use of slightly different hardware and software configurations for gateway versus standard motes,
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as described below.___j
4. HARDWARE DESIGN
The selection of components for the sensor motes is a critical process in the development of WISENET. Great functionality and low power are two of the highest priorities in evaluating the fitness of both the microcontroller and the sensor candidates. WISENET is introduced to the new state-of-the-art Chipcon CC1010 microcontroller with integrated RF transceiver. After a little research it was decided the CC1010 would make the perfect microcontroller. It had the following feature list: .1. Optimized 8051-core
Most of the early embedded microcontrollers use processor architectures that were taken from eight bit microprocessors. This is the worst way because the processor addressing is usually not optimized for accessing local hardware registers and their individual bits. Two devices which buck this trend are the Microchip PIC and the Intel 8051. The 8051 was designed from the prespective of what a microcontroller is and what it has to do. It included in the basic design was 4K of Read Only Program Memory, 128 Bytes of Internal RAM, a USART and 32 I/O Pins. The only major problem with the 8051 architecture is the twelve clock cycles per instruction cycle. This has made the 8051 appear non-competitive to other microcontrollers which can have as few as one clock cycle per instruction cycles
2.Active (14.8 mA), Idle (2.9mA) and sleep (0.2mA) power modes
When it is in active mode it takel4.8 mA to work and in the idle state it take 2.9mA and in the sleep state it take 0.2mA for the proper working of the microcontroller.
3.32 kB flash memory
Flash memory is a form of EEPROM_(Electrically-Erasable Programmable Readonly Memory) that allows multiple memory locations to be erased or written in one programming operation. Normal EEPROM only allows one location at a time to be erased or written, meaning that flash can operate at higher effective speeds when the systems using it read and write to different locations at the same time. All types of flash memory and EEPROM wear out after a certain number of erase operations. Flash memory is made in two forms: NOR flash and NAND flash. This makes it suitable for storage of program code that needs to be infrequently updated, as in digital cameras and PDAs. However its I/O interface allows only sequential access to data. This makes it suitable for mass-storage devices such as PC cards and various memory cards, and somewhat less useful for computer memory.
4.2 kB+128 bytes SRAM
5.Three channel 10-bit ADC
lObit Analog to Digital Converter (ADC) uses a four wire SPI interface. The 8515 processor has SPI hardware support built in and using it would have been fast with minimum software overhead. 10 bits is pretty high resolution. To avoid digital noise on the analog signals, added a separate +5V supply (78L05) devoted just to the ADC and the photodiodes used as inputs. The ground for all of the above was tied into one point where the power came into the regulator. With minimal bypass capacitors on the ADC inputs easily get stable readings
6.Four timers / Two PWM's
There are two essentially different versions of PWM: the original very lightweight window manager, and the newer Ion-based PWM2. PWM was the first window manager to implement "tabbed frames" or the back then unique feature allowing multiple client windows to be attached to the same frame. This feature helps keeping windows, especially the numerous xterms, organized. A look at the screenshots below might clarify the idea. Being a lightweight window manager with emphasis on usability, PWM discards some features common in window managers these days: only window shading in lieu of iconification is supported, there are no close and other window buttons (these actions are available conveniently through a menu), simple and elegant look instead of pixmapped themes, et cetera. PWM does have workspaces, menus and Window Maker dockapp support. It has pretty good keyboard support and almost all the functionality is configurable.
7.Fully integrated UHF RF transceiver (433 MHz / 868 MHz nominal)
The wireless transceiver contains at least two physical links, each with its own transmitter-receiver circuit in addition to digital and analog signal processing circuits to communicate with other wireless units using Orthogonal Frequency-Division Multiplexing (OFDM) protocol. The design approaches address the issues of noise interference between analog and digital subsystems, noise interference between two links on the same chip, and high-frequency self-test, measurement of funtional parameters (SNR, jitter, etc.), and interface between on-chip test facilities and external low-cost testers. The methodology is validated by a complete design, fabrication, and test of a case study selected in consultation with industry partners. _ Programmable output power (-20 to 10 dBm)
_ Low current consumption (11.9 mA for RX, 17.0 mA for TX at OdBm) _ RSSI output that can be sampled by the on-chip ADC
WISENET includes a socketed evaluation board (CC1010EB) and two evaluation modules (CC1010EM). CC1010 - The industry's first truly complete RF System-on-Chip solution! On a single die, the award winning 300 to 1000 MHz CMOS CC1000 RF Transceiver has been integrated with an industry standard 8051 microcontroller core. The CC1010 integrates a very low-power 300 to 1000 MHz RF transceiver and a 8051-compatible microcontroller that has 32 kB in-system programmable Flash, hardware DES encryption/decryption and a three channel 10-bit ADC. This means only a few external passive components are necessary to make a powerful embedded system with wireless communication capabilities, sensor interfacing possibilities and a lot of processing power.The evaluation board provided access to all of the analog and digital pins on the CC1010, as well as two serial ports, a parallel programming port, RF network analysis ports, and other peripherals. Each evaluation module featured the CC1010, RF network hardware, an antenna port, and an analog temperature sensor. The modules connected to the evaluation board via two sockets. These sockets also allowed the possibility of designing a custom expansion board.
WISENET is designed to measure light, temperature, and humidity. There are many digital temperature sensors available, but there is a much smaller selection of digital humidity and light sensors. A larger selection of analog sensors are available; however, analog sensors tended to require more power and be less precise than their digital counterparts, in addition to requiring more complex circuitry. For these reasons, digital sensors are given higher priority. Two new sensors provided the required functionality. First, Sensirion released the SHT11, a digital temperature and humidity sensor with ultra low power consumption (550 MicroA while measuring, 1 MicroA when in sleep mode), a 14 bit analog to digital converter, and the desired accuracy (±5% relative humidity, ±3°C). It also featured a simple serial interface. The light sensor chosen was the Texas Advanced Optoelectonic Solutions (TAOS) TSL2550 ambient light sensor with SMBus interface. This sensor also featured ultra-low power (600 MicroA active, 10 MicroA power down), a 12-bit analog to digital converter, and dual photo diodes. The TSL2550 uses both photo diodes to compensate for infrared light and to produce a measurement that approximates the human eye response.
The final stage of hardware design involved creating the Add-on module. The WISENET Add-On Module has the two digital sensors described above. The Sensirion SHT-11 humidity and temperature sensor has a 2-wire proprietary serial interface. The TAOS TSL2550 digital light sensor uses an SMBus serial interface. SMBus is a standardized 2-wire serial interface. The layout must be carefully designed such that the light, temperature and humidity sensor does not underneath the evaluation module when it is plugged into the board, which would make them useless.
5. SOFTWARE DESIGN-SHELF PRODUCTS
The server using for WISENET should have four commercial off the shelf applications installed on it that worked together to create the Data Analysis portion of the Server component.
Apache, MySQL, and PHP are open-source products freely available on the Internet. In addition, Chart-Director the trial version of the commercial application Chart-Director was used.
Apache is a standard web-server, which makes a web document available on the Internet. The Apache http server is a powerful, flexible, implements the latest protocols is highly configurable and extensible with third-party modules can be customised by writing 'modules' using the Apache module API provides full source code and comes with an unrestrictive license runs on Windows NT/9x, Netware 5.x and above, OS/2, and most versions of Unix, as well as several other operating systems is actively being developed encourages user feedback through new ideas, bug reports and patches implements many frequently requested features, including: