Friday, May 7, 2010

WSN-intro and Meshnetics breakout boards

A couple of years ago, first news about Wireless Sensor Networks started to appear on the Web. At the beginning there were scattered pieces of information, but slowly it became a recognizable and popular research direction. I really like the idea of wireless sensor networks - tiny, simple devices called "motes" with limited sensing abilities, and processing power are used to collect data about physical and social phenomenons. Single mote has very little usefulness, but a network of them can support really innovative projects. It really sparks up imagination.

The most popular standard in the WSN area nowadays is the Zigbee. It is supported by Zigbee Alliance - association of many international companies (among them Cisco, Atmel, TI and many other). However there are many other standards around - both open and proprietary. I recently became interested in 6LoWPAN - it's a collection of standards maintained by IETF - an international non-profit organization, that also maintains IP, and other Internet-related standards. 6LoWPAN makes it possible to use IP (only v6) on low-power radio links used in WSN.

After doing some research I determined that probably the easiest way to start doing some 6LoWPAN research is to use Contiki OS - operating system for embedded devices from SICS. Contiki already supports many 6LoWPAN concepts and many other are being actively developed. Contiki is available for many different platforms, but I think that MSP430-based devices are best supported. Contiki is equipped with java-based network simulator Cooja - so it's possible to start doing research without actually having any motes. I am getting ready to test that approach - I already installed Ubuntu Linux, and I hope to start some tests soon.

Regardless of the simulator I plan to do some test with real motes. For my development platform I chose Atmel/Meshnetics Zigbit ATZB-24-A2 modules. They are quite cheap, available in Poland and contain a microcontroller, a transceiver and an on-chip antenna. I found a very good French site which contains many useful comments about these modules. My first step was to design a breakout board for the Zigbit modules. Zigbits are quite difficult to solder without hot-air station. I don't have such a station, so I plan to solder the modules once and for good to these breakout boards, and connect the boards to other devices with simple pin headers. My breakout boards will also contain JTAG and power-supply connectors - so I should be able to do some simple programming and debugging only with breakout boards. Here is the picture of the finished board next to a Zigbit module:



I made some rookie mistakes with the design - I got the description printed over the pads, but in general it looks just like I wanted :) . Now I'll have to come up with an idea how to solder it right. Any suggestions?

7 comments:

  1. is it possible to post the breakout bord schematics / board layout ?

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  2. I was wondering, what the rage of these modules are? Have you tested them at all?

    Thanks

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  3. I haven't tested them for the range. I plan to use them for my home automation network, and their range isn't critical for me(10m is good). These are almost plain zigbit modules, so I think you can check range in their datasheet.

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  4. Hi Maciek,
    Thanks alot for the Sch & Board files.
    I tried to open them using Cadence OrCad 16.5, However it failed to open. Are these files meant for Cadence format?

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  5. Hi Kumar,
    these are files for Eagle PCB Design software. You can download free version from:
    http://www.cadsoftusa.com/

    ReplyDelete