Well, the Twitter thing is turning out pretty interesting. I originally made fun of all the people on Twitter because I had thought that it was only for people with nothing better to do than post the painful details of their lives. Actually, I found that I'm one of those people. I had a lot of mental resistance to joining it, but eventually gave in because all the people in Tokyo Hackerspace were using it and trying to convince me of all the wonderful things about it. After having used it for about a week now, I have to say that it is in fact pretty useful. I don't think it's for everybody, but it does have two very good qualities that I can see now. The first is that it's an excellent source of information. If you follow people that are roughly in the same industry as you, ie: wireless sensor networks, then you can see them constantly posting links to interesting topics that are relevant. It's especially important for me because I'm trying to aggregate WSN news so I'm always looking for new information sources. The other thing that is quite handy about it is that it's a good way to keep people posted on the status of the project in real time. If you just look at the blog, then it might seem as if the activity is slow. However there are a lot of things that go on behind the scenes that never make it to an actual blog post but can easily be thrown into a sentence on Twitter. I guess I should refer to it as a tweet, but I still find the term a bit embarrassing. In other words, for someone like me, Twitter is a very good communications tool to fill in the information gaps that the blog can't cover as well as find sources of interesting WSN tidbits.

Aside from that, I've finally sent the first FreakZ development platform board files to the PCB fab. The reason it took so long was because I had to verify both the MCU board and the radio board together. I went through three different radio prototypes before settling on the one I have now. It contains both an SMA connector and a chip antenna and either source can be selected by moving a DC blocking capacitor. I had originally thought to use just an SMA connector, but that proved to be a hassle. External antennas are expensive, bulky, or require cables so if you have more than one or two, it becomes unwieldy. Chip antennas are a better choice if you don't need the performance of an external antenna and just want the convenience of having something ready to go.

I decided to leave the SMA on as well though because there are some situations where an external antenna is much better. Chip antennas are not very efficient and the impedance is not always matched correctly to 50 ohms. That means that you may lose energy to impedance mismatch or simply losses in the antenna. Also, chip antennas usually radiate outward uniformly which is not always desired. There aren't many cases where I need to radiate a signal to my ceiling (Z axis) and would rather have the energy concentrated in the XY-axes. There are many excellent external antennae that are directional so if you know the direction of the receiving node, you can point the antenna at it and concentrate the energy towards it. That way, it's a better use of the available transmit power and you can increase the transmission range. There are some fairly inexpensive directional antennae in Akihabara that are 9 dBi which means that they have ~8x the power in the direction they're pointed at compared to a uniformly transmitting (isotropic, which is what the 'i' stands for in dBi) point source antenna. 

The initial FreakZ dev kit will consist of two main boards: the MCU board and the radio board, connected by a standardized connector. The reason they're separated is because I want the freedom to interchange different MCU boards with different radios.  That's also the reason why I'm standardizing my connector and pinout so that all boards can connect with each other. The initial MCU board will be an AVR, more specifically, the AT90USB128 which is the same MCU as on the Raven boards. That way, people that are already using the Raven can use the FreakZ board as well with basically no software change. The reason why you might want to do this is because it's almost impossible to prototype on the Raven boards which I found to be one of its greatest shortcomings. Although Ravens are great for doing protocol stack development, when it comes time to do an actual implementation, it's very difficult. 

That brings me to the third board, which is the breadboard peripheral. This board is the same as the Tokyo Hackerspace breadboard I designed for the hackerspace workshops, and it also includes a standardized connector. The MCU board's I/O, interrupts, SPI/I2C, and power pins are also broken out on the board so that it's easy to interface back to the microcontroller. The main feature is that there is a breadboard where you can quickly try out different sensors and circuits. That way, you can interface the sensor/control circuits to the MCU and communicate the data to other wireless nodes easily. It's basically the rapid prototyping platform that I wanted for myself, including the ability to swap out MCUs and radios which is one of the main points of having an open source stack.

If you remember, I had made some prototype boards previously and actually got two of them working. So in what little spare time I had, I actually set up a 4-node network which was quite nice. What was even nicer was that I was able to do the route discovery across the four nodes properly and communicate with the nodes on the end of the chain, while hopping the intermediate nodes. However I can't really do much real testing until I set up a somewhat larger network so I'll have to wait for the board sets to come back from the fab.

And finally, I'm putting together a couple of application circuits. One of them is an AC energy monitoring module which should come in handy for a lot of power monitoring applications. I'm hoping I don't electrocute myself during development but if it works out, then it might turn into an easy way to add energy monitoring to things like automated light switches/dimmers, or other apps. I'll keep everyone informed about how this goes.

In the meantime, I gotta get my ass back to writing tutorials. My tutorials section has been stagnating on the NWK layer for the past few months. Also, if you want to see what's going on with the project (or me) in real-time, you can check out my Twitter page . I'll try and see if I can figure out a way to publish the messages in a blog sidebar as well. 

Here's some pics of the boards I just sent out: