Wednesday, March 09, 2011

AT91SAM7S and Android help you bang bits

There are plenty of test instruments (oscilloscopes, logic analyzers, spectrum analyzers, etc) where you plug some hardware into your laptop's USB port, and the laptop screen shows a display that would have appeared on a cathode-ray tube in decades past. It's very cool that we can do this, and these USB instruments are much more affordable (and much much easier to carry) than the old-school stuff that I grew up with.

The BluetoothBitBang is a gadget that comprises two boards from Sparkfun Electronics. One is a AT91SAM7S-64 header board, the other is a Bluetooth serial interface. You can see there are also some AA batteries in there to power the thing. This connects over Bluetooth to your phone, running a free app available on the Android Market. You can use buttons on your phone's screen to set or clear six output bits, and you can read six input bits. The two boards cost $71, and if you're willing to do some fine soldering and use the bare version of the Bluetooth module, you can knock off twenty bucks. If I'm energetic, maybe I'll see about putting together some kind of significantly cost-reduced version. That might depend on the level of interest I see in the thing. I've posted a Wikipedia page with a lot more information, including the schematic of how the boards are wired up.

The SAM7 firmware and the Android app source code are both publicly available on Github. I'm an Android fan, but the Bluetooth protocol for talking to the board is quite simple and if anybody is interested in writing an iPhone or BlackBerry app for the thing, I'll be happy to provide some support to make that relatively easy.

I think this whole thing gets a lot more interesting when (1) you move from a phone to an Android tablet, which will be cost-effective as tablets flood the market over the next year or two, and (2) start building much more sophisticated data acquisition front-ends. This is just about the simplest acquisition hardware I could imagine that would still be worth the effort of building and debugging it, but no reason one couldn't do a Bluetooth-connected oscilloscope or logic analyzer.

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