DIY desktop glass multitouch/touchpad from a unibody Macbook
~6 months or so ago, I purchased a top case from a parted out 13″ unibody Macbook from eBay, with the intent to strip off the touchpad and make a DIY desktop touchpad USB device out of it. Similar things have been done before, albeit not for these glass touchpads.
I thought it would be a great way to create an amazingly comfortable mousing/typing combo by putting it between the two halves of my Kinesis freestyle keyboard, allowing me to minimize reaches for the mouse while maximizing comfort.
I have a similar setup I made for work, but since I only have the choice between Windows XP and RHELinux there, I just used this cirque touchpad. Comfort wise, it works amazingly well, but the cirque pad, quite frankly, sucks. No middle click, no two finger scrolling, terrible accuracy, yet I continue using it because the comfort level outweighs the negatives in my case.
Fast forward to this week. I had an interesting idea pop into my head earlier in the week, which was a potential way to get more information, or pinout/wiring diagrams of the parts I have, to move the project past its current standstill. The challenge is that the ribbon cable which connects the touchpad to Apple’s logic board is extremely small, has 3 ICs on it, and way too many tiny test points for me to realistically probe to pull this off.
I needed more information.
In the first link above, the older style touchpads incorporated the mouse’s USB controller IC into the touchpad PCB itself. On the unibody Macbooks, the combined mouse/keyboard USB controller IC is on the logic board (as confirmed by ifixit)
The 3 ICs on the unibody touchpad cable are:
Texas Instruments: CD3238
(google => RS232)
Broadcom: BCM5974
(google => touch controller)
SST: 25VF020
(exact match from SST, 2Mbit flash chip)
I’d rather not divulge the idea that led to this, but will say that the end result was several responses from someone at Apple. This person was kind enough to answer my questions, in return, I won’t give out that information. At any rate, this person is in a position to answer the technical questions I had, and the feared/unfortunate end result is that it would be possible to accomplish my goal… IF I had a logic board too, not just the pad and cables. The contact at Apple confirmed the only two options would be to tie in to the logic board upstream from the mouse/keyboard USB controller, or somehow magically figure out all the needed information to do it at the lower level (essentially duplicating the USB stuff on the logic board). All without any wiring diagrams or pinouts of the ICs.
The cheapest logic board I could find is $500, making this project too spendy to continue… Especially considering the fact that I can pick up a top case with the older style touchpad for ~$50 on eBay…
My end goal was a touchpad with middle click, and multi-finger swipe to scroll. While the other gestural capabilities would be awesome, I can live with the limited set available from an older touchpad, and so, one is on the way (only $40 even!).
When it gets here, the DIY will continue, and perhaps I can even coax it into supporting 4 finger gestures
If it succeeds, I’ll replace the crappy cirque at work too.