A lot of people waiting for the code release are probably wondering what the hell I'm doing. In fact, I'm even wondering that myself sometimes. The truth is, I've been spending all my free time in the last week and a half trying to design development boards for the stack. So I've finally finished the schematics for six different boards, three MCU boards, two radio boards, and a peripheral board. Designing the boards is actually quite fast, and if it were just a matter of putting the components together, then I think I can usually put together a board in a couple of hours. The problem is that component selection takes a long time. Have you ever seen the DigiKey catalog? That thing puts most phone books to shame.
One of the issues with component selection is finding a reliable supply of components. DigiKey has a habit of running out of components right when you need them, so I've been trying to choose components that are generic enough to have a second source supplier. On top of that, I'm trying to use components that I can source locally in Akihabara in case I get into a pinch in terms of delivery schedules. Along with that, you have to check the package sizes, draw the circuit symbols, the PCB footprint, and check the specs to make sure everything is kosher before you actually take a chance and throw it on the board.
The reason I needed to get the schematics out of the way is because I needed to place the orders as soon as possible. Once the orders are placed, then there will be a time lag that would allow me to do other things like finishing the docs and doing the PCB layout. Also, I wanted to grab the components off of DigiKey as quickly as possible because some of them were disappearing quickly. One of them was the DC-DC boost converter from TI (TPS61202) that can boost a 0.5V source up to 5V. I was planning on using these for my main MCU boards so that it would be easy to interface them to batteries and solar cells. Since they were new and energy harvesting is kind of a trendy thing in electronics now, they were disappearing quickly. I finally bought out the last of the stock from DigiKey so they're completely sold out until the next shipment. The MCU boards that use this chip will be a limited edition until the supply stabilizes.
Along with the wireless dev boards, one of the MCU boards I designed was for Tokyo Hackerspace. There are a lot of people there that are curious about electronics and want to learn more about it. So I put together a low cost board using a USB AVR (AT90USB162) with 16 kB flash. The board has the same modular connector that I'm using for my main dev boards so it can interface to the same peripherals. One of the peripherals that I created specifically for this board is a quick prototyping area using an adhesive-backed solderless breadboard. It's those white plastic things with a bunch of holes that you had in electronics lab back in school. Anyways, since the breadboard can plug into the MCU board, it will automatically have a 3.3V and 5V supply as well as GPIO, interrupt, I2C, and SPI lines. I think it's going to make a good learning platform for the people curious about electronics in Tokyo Hackerspace.
The plan is to make a "class set" of about ten boards that everyone can use free of charge and can also be used for a common platform for workshops, classes, and collaborative projects. If people want their own personal board, they can purchase it through Tokyo Hackerspace with the proceeds going to buying basic equipment like soldering irons, hand tools, meters, and scopes for the group.
Also, I'm thinking about what kind of workshops would be interesting. Along with basic electronics and programming, I'll probably collaborate with one of the other geeks on electrical/mechanical interfacing, and of course I think sensor interfacing will be quite fun. I'm also hoping that I can do some more advanced topics like embedded web servers using Contiki and uIP, and of course hands-on tutorials with the FreakZ Zigbee stack, but I'm going to have to wait and see on those ones since they require quite a bit of programming knowledge.
I'll keep everyone posted on how things go with this, but Tokyo Hackerspace looks like it's going to be fun and keep me a little busy. Here's some shots of the initial MCU and breadboard PCBs for THS. No, the tower in the logo isn't the Eiffel tower. It's the Tokyo Tower located in Roppongi and is part of the Tokyo Hackerspace logo. One of these days, I might even go check it out: