Our CSS Capstone Project goal was to construct a prototype end-to-end Wireless Sensor Network (WSN) system. This system provides for a challenging array of computer science topics from integrating embedded computing elements, low power sensor network optimization, XML messaging, XML compression, database interfacing, web frameworks, integration with cloud computing elements and user interface deployment within a virtual machine environment.
Major Development Areas / Accomplishments
Our project consisted of several subsystems including:
- Embedded Sensor Radio Platform -- A sensor platform consisting of an ARM CORTEX M4 32-bit microcontroller, Freestar 32-bit ARM/radio module, several sensors, human interface and and a power management subsystem. All of the code (Embedded C) was developed using the Freescale Codewarrior IDE environment as well as a custom (Real-Time Operating System) RTOS optimized for this WSN architecture. All of the hardware was custom design, fabricated and hand assembled (soldered) over the CSS595/596 project timeline.
- Wireless Network -- Initial goals were to integrate an off-the-shelf network called “PopNet”, but time and budget constraints drove us to a Simple MAC (SMAC) provided by the manufacturer of the Freestar radio module. This is provided as an off-the-shelf UART host RF protocol with a number of limited functions that allow for a master/slave, star network, or simple 1-2 hop repeater networks to be developed.
- Wireless Gateway -- One device that is essential to any commercial deployment of a sensor network is a gateway device to enable two-way communication to the IP backbone. This gateway provides flow-through communication of our sensor data from each radio device to the host Linux environment where we have developed a receiving matched XML translation and decoder functions for compressed XML data packets.
- XML and Compressed XML Protocol -- XML compression/decompression algorithms (Ruby) were developed as a part of our CSS600 independent studies. We will be developing actual compressed sensor data payloads within our embedded firmware that will provide maximum bandwidth utilization of the wireless sensor network channels. Currently we are testing the overall system with uncompressed XML protocol messages.
- Database -- A MySQL database was developed and models (tables) generated using the Ruby on Rails Active Record based framework. The database tables model entities within the agricultural application space consisting of Users, Orchards, Radios, and Sensors. (Currently in process)
- Database Service -- A database service will be developed that will allow parsing of incoming XML elements and insertion into the; (MySQL) database model. (Currently in process)
- Web Site - A Ruby on Rails website framework has been generated with a simple sensor database model. This will be further developed as the project site continues beyond the end of the Capstone project. All of these functions are hosted on the CSSVM which is an IBM Linux/VMWare server located in the UWB CSS department.
Our goal has been to develop a framework for an end-to-end WSN system. This was a quadruple challenge with disparate areas of electrical engineering and computer science distinct from each other. We were able to assemble most of the pieces of this framework and our continued plan is to conduct field trials in late June for this system on an actual tree fruit orchard in Wapato, WA, continue to expand the use cases both in the field as well as a the UW Bothell campus.
Figure 1: System diagram
Figure 2: Hardware components
Description: From left to right, top to bottom, the first picture shows the first completed assembly of the AgComm 2.4GHz radio device with the processor/radio/sensor board on the top case and a power management board on the back case housing. The power management unit has both a Lithium Polymer battery (under the PCB) and a 3-AA backup battery pack on the top (visible black structure). The middle picture is a front view of the radio showing the 4 waterproof connectors. The top right shows a precision machining operating needed to accurately position the connectors. The lower left picture shows the development configuration of the units where both the processor and power PCBs are joined together (prior to splitting for assembly). The lower right picture show a very chaotic (but functional) set up in the CSS graduate lab where heavy HW/SW integration work was being performed.
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