Development

The SquidBee open sensor network

By Forrest Cook
December 5, 2007

SquidBee is a project that uses an open hardware design as well as open-source software as a platform for remote control and sensing: "SquidBee is an Open Hardware and Source wireless sensor device. The goal of SquidBee is getting an "open mote" to create Sensor Networks." SquidBee uses the ZigBee self-organizing low power wireless mesh network protocol. ZigBee operates in the unlicensed 2.4 GHz, 915 MHz and 868 MHz ISM bands with data rates from 20-250 kbit/second, per channel. ZigBee is optimized for super low power operation so that the devices can be operated from battery power for long amounts of time. For long-running outdoor applications, powering the devices from photovoltaic panels would be an obvious technology choice. Using the 1mW XBee power level, the XBee maximum device-to-device range is 100 meters. At the 100mW XBee pro power level, the range is extended to 1KM. Each additional node can extend the range of the mesh network, since data passes through the nodes.

ZigBee is supported by members of the ZigBee Alliance: "The ZigBee Alliance is an association of companies working together to enable reliable, cost-effective, low-power, wirelessly networked monitoring and control products based on an open global standard".

The operation of SquidBee is described:

How does SquidBee work? 1. Acquires values from environment parameters: temperature, humidity, lightness, presence, pressure or (almost!) whatever you can sense. 2. Operates with these values, when required. 3. Transmits these values using a low power consumption wireless technology (ZigBee). 4. Sleeps until next timeout and repeats from the first step. Second step is not always necessary, depending of the calculations needed it may be better to make them in receiver computer to save nodes energy.

SquidBee is built on top of the Arduino open-hardware prototyping platform: "The Arduino board is a cheap, robust i/o board based on the ATmega168. It has 13 digital pins (6 of which allow PWM output) and 6 analog inputs. There are USB, serial, bluetooth, and mini versions, which you can buy or build yourself. Note: The reference designs for arduino are distributed under a Creative Commons license ". An add-on MaxStream XBee Shield board and a power source are combined with the Arduino board to create the SquidBee node. See the SquidBee Data-Sheet [PDF] and the XBee Data-Sheet [PDF] for technical specifications.

Communication between a Linux machine and a network of SquidBee nodes can be accomplished by turning a SquidBee module into a gateway node and connecting the gateway to a Linux machine over the USB bus. The example Receiving data with the Gateway in Linux software shows how to achieve basic communication with the mesh network. The recently launched Zigbuzz project is working on an in-Kernel device driver for USB-connected ZigBee devices, no software has been released yet since it is still in the design phase. A Libelium MeshLium Router box can be used to connect a ZigBee wireless network to an 802.11 WiFi network. The SquidBee software page includes a control program for the Arduino board, other utilities and some example programs.

Some of the possible uses for the SquidBee technology include home automation, scientific data collection, remote control and security systems. The project has documentation (in some cases placeholders for documentation) on using a variety of I/O devices including: generic analog and digital sensors, light and temperature sensors, ultrasonic range finders, GPS modules, accelerometers, switches and LEDs, LCD displays and beepers. Although not listed, remote cameras, motion detectors and more weather sensors seem like obvious additions.

If you are looking for a convenient way to extend the reach of your system''s peripherals, SquidBee looks like the right project for the job.

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