I’m proud to announce the release of two new designs, the Arashi Ethernet Gateway for both 2.4 GHz and 900 MHz wireless sensor networks. There’s quite a bit of history for me with this design. Back when there was a meltdown at Fukushima Dai-Ichi in Japan, I grabbed some Wiznet W5100 ICs and put together a circuit that connected to and uploaded radiation data to servers on the internet. This eventually became a design I called the NetRad and was one of the first DIY geiger counters to be uploading radiation data publicly to the internet during the Fukushima crisis.

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In Tokyo Hackerspace, we deployed a few of them when Sean Bonner emailed me to ask me for links to the data and if I wanted to help a fledgling group that he and Joi Ito were working with called RDTN. Later on, Sean, Joi, me, Bunnie, and a cast of others started working together and Safecast was born .


Here's a shot of one of our first meetings together in Tokyo with Bunnie, Aaron Huslage, Sean Bonner, Joi Ito, Ray Ozzie, and a bunch of people from Keio University.

At the time, geiger counters were completely unavailable which was the main reason we had to build them ourselves. Since we kept on adding to the number of networked geiger counters we had, we eventually caught the eye of a company in Japan called Softbank. They’re a large phone service provider in Japan and recently purchased Sprint in the US. The owner, Masayoshi Son, is the richest man in Japan and interestingly enough, even having a lot of money couldn’t get you geiger counters at that time.

I was asked to attend a meeting with Softbank and Keio University. At the meeting, Softbank mentioned that they wanted to fund a buildout of the networked geiger counters across Japan. They put in approximately $1M into a Keio research fund, I became a Keio researcher that night, and hence the NetRad radiation sensor network project began. All-in-all, we deployed around 400+ networked geiger counters at various locations around Japan and the data was used to analyze the radiation in the area and also understand how the radiation decays and disperses over time.  I was  very impressed with the Wiznet W5100 IC and the Arduino ethernet library and the combination was extremely stable and easy to work with.


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In any case, that’s my first experience with the Wiznet/Arduino Ethernet combination and it was great. It’s simple, reliable, and widely used in the embedded community so there’s a good base of support for it. It’s definitely one of the easiest ways to get sensor data out on to the internet. For the Arashi gateway designs, I also made a few modifications which I think are important.

The first modification is that the ethernet board also has a wireless radio on it. This is important because the main purpose of these boards is to be a gateway from the local sensor network to the internet. The sensor network data can then be uploaded to internet servers and accessed anywhere. This required some slight patching to the Arduino ethernet library to make the SPI (serial peripheral interface) accesses atomic. Otherwise, the stock ethernet library doesn’t play well with other interrupt-driven devices on the SPI bus. This is covered in more detail in the documentation and will probably be the subject of a separate post.

Another modification I made is that this board uses an ATMega1284P, a much beefier MCU than the standard ATMega328P. The ATMega328P has 32 kB flash and 2 kB RAM. If you’re using the TCP/IP/ ethernet library and DHCP, that can easily chew up over 20 kB flash. Also, the 2 kB RAM constraint is tight for an internet enabled application and makes dealing with web APIs or parsing text difficult. I ran into the situation multiple times where I had to trim or optimize code to fit into an ATMega328P which is why I decided to go with a bigger MCU. The ATMega1284P has 128 kB flash and 16 kB RAM. This pretty much removes any resource constraints for most applications unless you’re doing something really big. In that case, then it’s probably best to move up to embedded Linux.

The ATMega1284P is a non-standard MCU for the Arduino environment so certain library files need to be installed so that the Arduino IDE can support it. Most of the core library support is based off the Mighty1284P project which has been tested and works well with the Arashi gateway. Full instructions on installation and getting the board up and running can be found in the documentation. Also, the pinouts for the ATMega1284P will be different than the ATMega328P so there might be some porting required with certain libraries. Because of that, this board is probably best suited for an intermediate Arduino user. However if there are any questions, feel free to email me, post them as a comment, or post them on the forums. I’ll do my best to help clear any issues up.

I guess that’s about it. I hope you enjoy this board. I’m really happy to be able to finally release this board and I think it will make a great companion to the Freakduino series of wireless boards.
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The Arashi 2.4 GHz Wireless Gateway board can be found at the FreakLabs shop here.
The Arashi 900 MHz Wireless Gateway board can be found at the FreakLabs shop here