I've got a big update regarding the Bluetooth implementation!
The last couple weeks I've been finalizing the design for the Bluetooth interface. I've learned a lot through the research as well as comments and suggestions from backers (I feel I have a very brilliant team of people helping here!). My original plan was to use traditional Class 2 (low-range) bluetooth via Roving Networks RN-42 module. Max (an iPhone developer in Germany) informed me that the iPhone does not allow data bluetooth connections without a special Apple Authorization coprocessor chip, which must be purchased from Apple. The chips only cost $0.60 each, but the project must first be submitted to Apple (MFI program) and then wait for approval, a process which can take anywhere from 2-6 months without guarantee of acceptance. Compatibility would not be a problem, however, with most Android phones. (I'm generally an Apple fan, but not over this particular issue!)
While communication with smartphones was never my main reason for bluetooth (it's primarily for connecting to future accessories and other Timelapse+ devices), I still wanted to be able to use it with the iPhone. However, trying to get accepted by Apple's MFI program wasn't very feasible at this point.
This brought me to Low Energy Bluetooth (also suggested by Max -- thanks!), a part of the new Bluetooth 4.0 specification. LE Bluetooth devices do not require approval by Apple. They are also better for multi-point networks and WAY better in terms of power consumption. Accessories for the Timelapse+ could literally be powered for years by a single coin-cell battery. Additionally, it has a much lower latency, providing quicker response times for future remote triggers and sensors.
The only drawback is that only the iPhone4S and the very latest android phones support LE Bluetooth. As a brand-new technology, existing support is limited but sure to expand in the near future. I'd assume that most new devices from here on out will be supporting LE Bluetooth. What I'm excited about is that it's much better suited for this type of device, and uses a fraction of the battery power of traditional Bluetooth.
- Way better battery life (potentially years for accessories)
- Faster to setup ~3ms connection setup time (compared to 6 seconds for pairing conventional Bluetooth)
- Lower latency
- Limited support from existing devices (currently only the iPhone4S)
- Slightly more expensive (but it won't change the price for backers!)
So I've decided that Low-Energy Bluetooth is the best form of a wireless interface for the Timelapse+. Being a cutting edge technology, the LE module is about 40% more expensive than the original module, but it still fits within the budget for the Bluetooth version of the Timelapse+, meaning the advertised price of $129 will not change (until after Kickstarter). I'm now planning on using the BR-LE4.0-S2A module from BlueRadios.
Thanks again for your support! I'm excited to make the Timelapse+ the best possible!