(Intuos2 Serial 6x8)
There is a similar mod for the GD-0912-R here: (http://forum.bongofish.co.uk/index.php?topic=1927.0
EDIT: This was the first mod I did and it might be a bit difficult to read. Since one person recently claimed to want to perform this on a XD-0608-R mod, I will re-write this post and also talk how to hook the teensy, etc.
Supply advertised as 9v-12v 0.1A --
EDIT: With the mod described below, the board runs at 5v and pulls around 55mA when idle and ~60mA when sensing a pen. (This is with the 5v power regulator and serial driver disabled).Warning: This mod will permanently disable the external serial & power connections. Playing with electronics is not without risks. You can break or burn anything including your fingers.
The board was obviously built to be the same for USB and Serial. The biggest missing IC has the "USB" letters in it. As usual, the serial driver chip is present (ADM202) and there is what looks like a power regulator.
I am almost certain that I could connect my Teensy board in there (by removing or partially unconnecting the ADM202 chip) and (maybe) removing the voltage regulator as well. There are a lot of special Serial signals (CTS, DSR, DTR) (the same ones as we saw with Undersampled's TabletPC sensor). I just hope these we can all connect either to ground or VCC only leaving TXD and RXD as active serial signals.
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Pinout from the ADM202 datasheet:
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EDIT1: The serial markings are all "reversed" -- The names are the ones from the DTE side which was totaly confusing. I finally found the "real" serial pinouts and their usage by following the DB9 connector and the ADM202 pinouts to correlate to be sure. The markings didn't make sense since a pin like "DTR" is coming from the PC normally but according to the ADM202 pinout it was going the other direction!
EDIT2: I was able to run the tablet only with a FT232R (TTL) sparkfun breakout board configured for 5V. The board provides both the 5V power and RXD/TXD lines. The 2 serial control signals (DTR & RTS) coming from the PC needs to be "grounded" (connected directly to ground) -- that is necessary else the board won't transmit coordinates. I was able to configure the Intuos2 and see the data on the virtual serial port. This confirmed me that I will be able to substitute that with a Teensy in similar fashion as the tabletPC (but using a 5V supply -- no need for the 3.3v regulator).
Actually even if the DTR & RTS are high, the wacom will still allow transmition of config data like ~C<return> which outputs the max X and Y coordinates in plain ASCII.
The ADM202 can drive 4 serial signals. Two incoming and two outgoing. Well, there are 5 serial signals. So the fifth control signal is handled by analog parts (components in the corner near the connector, the main output being some sort of transistor - TR1R). The ADM202 (and the analog for the fifth signal) has pullups on the TTL signals side. This is a bit of a problem and it took me a while to find that they need to be grounded. So the course of action here is really the remove the ADM202 chip as well as the TR1R "transistor".
The regulator needs to be removed I think to avoid weird electrical states and 5V needs to be feed in place of one of its leg. One way to "avoid" removing it is to simply "cut" the leg, lift it and solder on the pad.
EDIT3: the board works initially at 9600 but then you can switch to 38400 with the "BA38<return>" command. You then have to send a "ST<return>" so it starts sending coordinates. (All that info I have found in the linux driver). This is known as the Wacom Protocol 5 (V) it seems. I got +/-900 CPS (character per second) reading on my "realterm" software. For 9 character packets, that makes 100 samples per second.
EDIT4: Here is a snap of the modified board:
XD-0608-Rmod.jpgExplanation of the mod:
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The numbers on the board : XD-0608 PWB-A483 - XABC GCMK-C2X
(The serial signal names below are from the DB9 connector not from the markings on the PCB).
The power regulator TA7805F has been "disabled" by cutting its leg on the red marking, this is where we inject the 5v input (red wire going to Teensy VCC). The wire is on the PCB pad, it is not touching the regulator leg. (difficult to see)
The ground can be connected in a lot of places, I picked the connector leg at 6
(black wire), but probably it would have worked on any of the ground "plane". (Connect to Teensy GND)
The ADM202 chip has been removed.
The TR1R transistor has been removed (serves the same purpose as the ADM202 chip).
The serial signals coming from the PC/Teensy other than TxD needs to be grounded:
is RTS, connected to B
and is connected to ground with the long yellow wire.
is DTR, connected to ground at 2
The serial signal (other than RXD) coming out of the intuos is left unconnected (the second ADM202 chip pad 5
The RXD signal is at 3
-- this is the main place where the intuos2 reports its coordinates. The most important signal! (Connect to Teensy D2)
The TXD signal is at 4
-- this is also quite important since I think the tablet won't talk without being told to. (Connect to Teensy D3)