From time-to-time we’ve been frustrated by the lack of backwards compatibility for Apple accessories. We have a great Monster FM transmitter that used the screen of the original iPod to select a channel. That was a feature we just loved which it never worked with any future hardware. We may not be able to get that back, but perhaps this hack can help us implement the ability to charge newer Apple devices using older accessories.
Seen above is the mounting dock from the iPod Hi-Fi speakers released back in 2006. Apparently the sound out of this set of speakers is just great, but you won’t be able to charge your modern device while it’s playing music. That is unless you’re not afraid to solder on a few simple components and roll in a switching regulator which can source at least one Amp of current. As we’ve seen in the past, Apple uses a couple of voltage dividers to identify modern chargers. These are installed on the D+ and D- lines of the USB connector and are pretty easy to recreate if you know the voltage levels the device is looking for. In this case a 39K, two 51k, and one 75k surface mount resistors are free-formed right next to the connector on the Hi-Fi’s dock PCB. The regulator on the right supplies the juice for charging. It’ll charge modern devices now, and even work with the iPhone five if you use a simple dock connector adapter.
In middle of all the adding features that should have been available day-one, Apple announced something really interesting for the hardware hacking community. The new iPhone 3.0 OS will support application communication over bluetooth or through the dock connector using standard or custom protocols. From Engadget’s coverage:
10:19AM “They talk over the dock, and wirelessly over Bluetooth. Things like playing and pausing music, getting artwork — or you can build your own custom protocols.”
10:19AM “Now here’s a class that we think will be really interesting — medical devices.” Scott’s showing off a blood pressure reader that interfaces with the iPhone — wild.
10:18AM “Here’s an example — an FM transmitter. With 3.0, the dev can build a custom app that pairs up with it, and automatically finds the right station and tunes it in.”
10:18AM “With 3.0, we’re going to enable accessory developers to build custom apps that talk directly to that hardware.”
No solid connection specification has been published yet. We’re excited about the prospect of developing our own accessory hardware, but we wonder what sort of hoops you’ll have to jump through. Apple doesn’t have the best track record when it comes to approvals. Just this week they denied MSA Remote client App Store entry; it’s a multitouch client that uses the standard TUIO protocol. Prepare for similar roadblocks in the future.