dash7

[Amir Tahvildaran]

Anyone familiar with or experimented with dash7?

http://en.wikipedia.org/wiki/DASH7

It's at the top of my want-to-play-with technologies but I never seem to get there.

I've never used any ZigBee stuff.  I'm not sure what it means for ZigBee to be proprietary but Dash7 seems to have some other  advantages over it as well.

Are there other low-bandwidth wireless protocols people have used or heard about?  

-Amir

[Sean McBeth]

ZigBee being proprietary means you have to pay a licensing fee to build hardware that uses it or to have their development kit, and you are restricted in how you distribute your code. Spencer Russell can tell you more. This Dash7 thing is interesting.

-Amir

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[Amir Tahvildaran]

Yeah - I'd love to hack around with someone on some dash7 stuff.  I got the TI MSP wireless kit (CC430 I think) but never seem to be able to unpack it :-)

-Amir

[Spencer Russell]

Interesting. There's a reasonably-priced devkit available at http://www.wizzilab.com/solutions/wizzikit/. 100EUR instead of a 600 to a few thousand USD for your average Z-Wave or ZigBee devkit from the major vendors. I can't tell what kind of software it comes with, though, and how much of the standard they implement for you.

It looks like there is an open-source dash7 stack available at http://www.indigresso.com/wiki/doku.php?id=opentag:main.

There's also a form where you can request the specification at https://docs.google.com/spreadsheet/viewform?formkey=dGhNVkNMZGlPR1M4anF6T0MzY0ZDNmc6MQ#gid=0

With ZigBee, what you pay for is to join the ZigBee Alliance, which gives you access to all the documentation and specifications. Typically you also will pick a vendor from whom you'll buy a devkit. The devkit usually includes their software stack on top of which you build your application. The stack code usually comes without a per-unit license, but it only runs on their chips, which is where they make their money. Your vendor is also the one who provides support when you run into trouble, either with understanding how the standard is supposed to work or with their software specifically. Most wireless vendors will also supply development tools like wireless sniffers, code generation tools, tools to send and receive messages from your computer for testing, etc.

I've never worked with the MSP430 wireless stuff, but from what I can tell it only implements the low-level raw-byte communication, so you still need to implement a data protocol on top of it. Looks like you can do Dash7 on them, actually.

A big part of having standards like ZigBee, Dash7, Z-Wave, etc. is interoperability between different devices. If you're looking to do a hobbyist project that may not really be a concern, so you just want a way to get raw data from point A to point B for which there are numerous solutions.  The other piece that you get from building on top of a standard and a vendor's stack is that all the messy routing and network management functions are already implemented and abstracted behind an API, rather than needing to implement it yourself. If you're interested in having a mesh of devices that can route through each other, or having a defined process for joining and leaving the network, or rediscovering and rebuilding routing tables, etc. then building on top of an existing standard starts to make sense. Battery-operated devices add a whole new level of complexity, as you need to figure out how to let a device sleep most of the time. For devices that only send data (like most sensors) this isn't an issue, but if you want the devices to be able to route through each other or if the sleepy device needs to be able to receive data, you need to come up with a synchronization mechanism, or some sort of parent-queue that holds messages for sleepy devices.

Someone has to write all that code though, and it's nontrivial and a relatively small market (as opposed to say, the internet, but it's growing fast), so there aren't as many open-source projects implementing them.

Check out http://freaklabs.org/ though, he's got some good info in there and has implemented a substantial part of the ZigBee spec.

[Spencer Russell]

On reading a bit more, it seems like some of the CC430 kits may be a good fit for Dash7 development. It'd take a bit of digging to see how they compare to the wizzilab one. on price and performance.

-s