PowerTap & Bluetooth 101
Back in 2003 we introduced the wireless PowerTap, which was the first-ever wireless power meter. For the most part this desire was born from my own frustrations of installing wire kits on countless pro race bikes, not to mention TT bikes, home bikes and spare bikes. We did extensive testing that summer at the Tour de France, where we used a very early version of ANT+ wireless technology. Fast forward to today and ANT+ is somewhat ubiquitous, but lately there's been a new kid moving to town: Bluetooth.
The standard version of Bluetooth—used in the effective but dorky ear pieces—consumes too much battery power for use in today's ultra-low energy sports sensors, so the member companies of the Bluetooth organization decided to create a new version of the technology. This new lower power Bluetooth has gone through several name changes but seems to have settled on Bluetooth Smart.
PowerTap engineers have been actively contributing to the advancement of Bluetooth Smart for our applications since 2011 because, with most smart phones having chosen Bluetooth Smart as their preferred protocol for connecting to 3rd party applications, it seems unavoidable that it will soon have a big impact on power meters. What exactly this means for ANT+ remains to be seen, but we feel there will be a number of different scenarios where ANT+ could be a preferred technology.
While it may seem like a straightforward evolution and the end of the story, there are some complicating factors when implementing this new technology, and we think it's important to understand some of these issues when mapping out your own solutions relative to which devices to use. Not much of this has been discussed because it can be a bit confusing and probably won't matter in about 6 months, but as a company that has products using both ANT+ and Bluetooth Smart we thought we would share our knowledge.
When implementing Bluetooth Smart, or ANT+ for that matter, it needs to be understood that there are a few support layers which manufacturers have to navigate to get the best solution for their customers.
Bluetooth uses a "master" and "slave" architecture where sensors and displays have a very defined and exclusive relationship. This means once you pair a speed sensor, for example, to your phone you can't pair that sensor to anything else. The phone controls the sensor and has to release it either by shutting off Bluetooth or using a disconnect feature in the app. Apple created a custom solution in 2011 for their iPhone 4S release, but bike computer manufacturers are waiting for suppliers to integrate this technology into the microchips they provide.
Chip manufacturers are busy getting prototypes into the hands of developers with a reasonable amount of functionality, including master capabilities. This is why you primarily only see sensors being offered on the market today, with minimal head unit options. If you go down the Bluetooth sensor route right now, the iPhone 4S or newer is your only real head unit solution. There are some creative bridge products but they all require your phone to be present and actively relaying data. In addition to the now available PowerTap iPhone mobile app that is compatible with Bluetooth Smart sensors, PowerTap is working on a Bluetooth Smart equipped head units that will offer all the functionality of our current Joule GPS, along with some exciting new capabilities like ability to pair to both ANT+ sensors and your phone, as well as real-time or post ride data transfer via Bluetooth Smart.
The next hurdle is what's referred to as the Bluetooth stack. Chip solutions come loaded with specific software for various applications within the Bluetooth ecosystem. This software is called a stack and manufacturers either need to buy a solution with the appropriate stack or be able to update the stack at some stage of the production process. In our case we're dealing with a fully loaded sports stack inclusive of one of the newest released protocols for power but it also includes heart rate, speed and cadence. To date, there are no production solutions available with this stack already loaded. To make matters worse, there are no versions that allow chips to be updated from slave to master but solutions promising these features plus dual-mode slave AND master are also being promised.
To make matters even more challenging (and exciting) are a new breed of chips that promise to be able to support ANT+, Bluetooth Smart, Master and Slave capabilities at costs LESS than the currently available half-baked options. These super chips also promise more efficient battery usage and to top it all off they have more code space for custom firmware solutions and horsepower in the form of processing speed and support. We're actively working with these solutions as they become available (as is the rest of the industry) and will be able to offer our customers a number of solutions but 'when' is the question on everyone's mind.
We're as eager as you are to start rolling more products taking advantage of all the newest technologies but we're not always in control of all the pieces so it most of the time it takes much long than we'd like. Regardless, the future will certainly offer an even easier to use power meter because of these new options and PowerTap is prepared to lead the way.
- Jesse Bartholomew, PowerTap Category Manager
Follow Jesse on Twitter @powertappro