Step 7: The Digitising Heart of the MacTab

Picture of The Digitising Heart of the MacTab
Without this step, our tablet would be nothing more than a glorified, heavy electronic picture frame (with no means of control!). So, its time to find, hack and fit our means of input: a Wacom digitiser.

Now, after you read this step, you must pay the good folks at BongoFish a visit ( http://forum.bongofish.co.uk/ ). They are the grand-masters at making these kinds of devices, and I spent a good few many hours scouring the details. What we do in this step is this:
- Find a TabletPC digitiser and appropriate pen on eBay or elsewhere.
- Once delivered, cut the motherboard connector and attach to the Macbook bluetooth cable
- Test it.
- Fit it and rejoice!

On eBay, type in "Wacom Digitiser" into the search box. Now, you want to look for digitisers which have been in a HP TX2000. You will also want them to come with a cable (these are rare, and making your own is difficult). You will also want a digitizer pen that is compatible with Penabled Tablet PC's. All of this can be found on eBay.

(Other Wacom digitisers are available, but I have neither tested these nor know if they work with USB. To be on the safe side, spend a good deal of time in the BongoFish forums!)

The TX2000 is a 12.1" sensor board. You're probably thinking "But my Macbook is a 13.1" screen! I'm missing out on a one-inch border!". It's true, at the moment, the pen is absolute to the sensor, which makes my pointer move at a ratio of just over 1.08 times further from the centre. Its annoying, but until I work out a way to make a Mac driver for it, its an annoyance you have to deal with!). Normal Wacom drivers don't work with this sensor board at the moment, but I'm working on it...

I found mine for £25 and the pen was also £25. Once delivered, i stupidly cut a tear into the bottom left corner of the digitiser. These are really fragile, so treat with care! My digitiser still works, but the pointer goes a bit nuts in the bottom left area!
Remove the cable from the digitiser baby-board, and put it to one side. Remove the Macbooks' bluetooth cable, and set it to one side. You can remove the bluetooth module too; it's useless to us now!

The Wacom board is powered by 3.3v only, so a normal USB connection (5v) will likely render it useless. Thats why we use the Bluetooth board; it is the only 3.3v USB module in the Macbook. (I tried using a voltage regulator, but the voltages were a bit suspect! At least this method is tried and tested!)

You need to cut the and solder the cables according to the diagram in this thread ( http://forum.bongofish.co.uk/index.php?topic=1894.msg13834#msg13834 ). Having been a few months since I finished soldering, there seems to be more activity on the forums regarding this digitiser now, and so I'm sure the folks there can help you out if you run into difficulties!

I cannot speak highly enough about that forum. It is a remarkable font of knowledge!

Once you've finished soldering and insulated each solder join (don't want any crossed wires!), plug it into the Wacom baby-board, and the other end into the old Bluetooth connector on the motherboard. Power on the MacTab, and using a USB Keyboard and Mouse (or if it works straight away, the Penabled pen!) to the System Profiler. Under USB Device Tree you should see a ISD-V4 with the magical word "Tablet" next to it. Your pen should also be moving the pointer around (when waved above the sensor) and you should be able to tap-click!

Congratulations, your digitiser works! Now, centre it on the back of your LCD Display, and test it. Once you're happy, tape it to the back using electrical tape. Test on the screen, and there you have it, a home-made Tablet!