My New Project: The MagSafe Dell
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My New Project: The MagSafe Dell

by evilroot on Sun Sep 27, 2009 1:34 am

So, after building a bunch of Wavebubbles and some other random stuff I've decided I need something that will really be a challenge . . . . and be awesome in the process. I've already made quite a few modifications to my trusty old Dell D600 laptop, but now I want to make one to end them all . . . . modding an Apple MagSafe connector into the side!

The idea is not to replace the Dell connector, but rather to supplement it. I have various adapters all over my workshop (I have a computer repair shop), and the two most common are Dell barrel-style and Apple MagSafe (yes, I work on Macs. Love/hate relationship). I'd like to be able to use EITHER, whichever I have handy, and keep a MagSafe in my laptop bag since its a lot smaller and easier to use than the big Dell one.

So, as I've been researching I find this project is going to have some pretty major hurdles to clear. First and foremost, that of adapter signaling. Dell adapters don't have just two pins (pos/neg), they have three . . . . the center pin is for data, and tells the laptop what type and wattage of adapter is connected. Without this data, the laptop will not charge its internal batteries. And that just wouldn't fly. So I need to spoof this data when a MagSafe is attached to report to the laptop that a Dell 65W adapter is present. This page (http://www.howtofixcomputers.com/forums ... 08608.html) had a lot of information on the issues I'll be facing.

Second, the MagSafe has the same problem, but in reverse. The laptop tells it whether the battery is charged or not, and presumably what type of laptop it is. I'm assuming it's handled in this manner, I can't imagine its as simple as the laptop using the center pin of the MagSafe to just toggle the LED. If that were the case, than the higher wattage MagSafe's wouldn't do crazy things like change voltage when the battery is charged. This protocol is far less well documented. I suspect HEX dumps and some component snooping will be in order. I won't consider this project a success unless the MagSafe's LED functions as it should . . . . orange when the batteries are charging, green when they're full!

I'm thinking of building this project on a small SMD board using an ATtiny and some buffering. I'll have the microcontroller essentially play both sides and tell the Dell it's got a Dell adapter and the MagSafe that its connected to a Mac. There's a lot of empty space in the D600 chassis still, and I can always dremel in some more if needed for the board. I might change the control plans if I can think of a better or simpler way. Anybody have suggestions or thoughts while I'm still in the brainstorming stage, or know something about the protocols used in these adapters? While I can't promise how long it'll take, I'll keep this thread updated with current progress and build info, and post all the schematics/board art and firmware when I'm done!
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Please be positive and constructive with your questions and comments.