The kitchen node I described in the previous post has a USB port. Why?
Because the kitchen will also house the user interface. As I mentioned before, I initially looked at the Raspberry Pi. But I wanted a nice touch screen to go with it, and they aren't cheap. And then I realized that by the time I add wifi, sound (for alarms, if nothing else), and power, I might as well get one of those cheap Chinese Android tablets. I'll save all the hassle of connecting the display and touch screen, and have a powerful environment to program the UI.
So, somewhere mounted on the kitchen cupboards, we will have a nice 7in tablet, talking to the Jeenode using USB. The one I've ordered (Ainol Paladin) is not the cheapest available, but it's the cheapest running Android 4.0 (so I can play with the newest Android version), has a capacitive screen, and it's not one of the (reportedly) underpowered VIA 8650 based systems. Apparently, the VIA chip is on its way out, to be replaced by something faster. I would have liked an Allwinner 10 based device, but they are more expensive.
There remains the question how to connect the tablet to the jeenode. One option I found is a low-level debug mode based connection as used in the IoIo. That's supposed to work on most devices, but the ioio is a bit more expensive, and since it's not actually an arduino-type node (more of a dumb direct io extension of the android device), driving an rfm12b wireless node off it is not straightforward.
The other option is based on Android's new Open Accessory Development Kit. Not all devices support this mode, and because the USB host in this case is the arduino, it needs a more powerful (and expensive) mega based node.
But don't tablets support USB host mode? After all, most of them come with external dongles with ethernet and additional USB ports? That wouldn't make sense if they only could work as USB clients.
Indeed they do, and as this great post describes, it is possible to connect Arduinos as simple serial clients. Perfect.
At least, that's the theory. The tablet will come tomorrow (and there's always a worry about quality with cheap Chinese devices), and the jeenode parts have shipped from Holland as well. We'll find out.
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