peanut-butter-and-jam-sandwiches! Pof! USB plug magically sticking out!
Ok, I'll try to summarize electrical interface in this post. 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.
It might look complex/intimidating, it isn't really. There are only 4 wires going to the Teensy and 2 others staying on the controller board. There is just a lot of text and explanation, that's all.
Please read it all before doing anything.
There are many ways of connecting the power and serial signals with varying levels of difficulty/cost/risk. This post only talk about the coolest/cheapest/riskier one. It permanently destroys the tablet external power & serial interfaces. (An "extreme" alternative solution wouldn't even need to open the Ultrapad case: it would be costly but also the safest for the tablet). NOTE: such a solution exists and was done by Sicarus http://forum.bongofish.co.uk/index.php?topic=1993.msg17274#msg17274 Test
Like I said, this will break functionality. So if it does not work, you cannot "go back" to what it was before. It is thus important to know that stuff works (as much as possible) at every step. For example, if you have the board in your hands try it to see that it works before. If you do not have the pen, wait to get the pen before proceeding for the mod. You need to know it works before.
By trying I mean to (find a way to) power up the board and touch the tablet with the pen (both with the tip and eraser) and try the sideswitches. The "Led" should blink accordingly. If you see this, you are in pretty good shape. If you do not have the power adapter to try this, then you have no choice but to skip this and try to hook the ground and power and do that test.Test the Teensy alone
Simply connect it (with a usb cable) to the computer. You should see the led blink. This is the built-in software that paul programmed just before sending it to you. Of course, disconnect from computer before doing the soldering.Multimeter
This can be done without a multimeter or continuity tester, but it is always better to have this type of tool around to check on every soldering. You can double-check if you connected to a nearby circuit by error or stuff like that.Explanation of the modSerial Signals
There are 6 serial signals. They are not all needed. They go through a serial driver chip, the MC145406. Here's the pinout of the chip (with the voltages while powered with no serial cable).
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Combined pinout of the serial cable up to the "TTL side" of the MC145406 (PC-DB9 is on the computer). The teensy understands the TTL signals. So we are essentially replacing all this.------ Serial Cable ------ ----- MC145406 ---------- --Teensy-----
PC-DB9 Dir. DB9-Tablet RS (CP) Dir TTL (CP)
-------- --- ---------- ---------- --- ---------- -------------
2-RXD <-- 2 7 (CP135) <-- 10 D2 (RXD)
3-TXD --> 3 6 (CP136) --> 11 D3 (TXD)
8-CTS <-- 4 5 <-- 12 (CP145)
7-RTS --> 5 4 --> 13
4-DTR --> 6 2 --> 15
5-GND 7 *** Ground Plane
9v..12v 8 *** Power
6-DSR <-- 9 3 <-- 14 (CP148)
Pins not listed are N.C. (Not Connected)
Summarizes the modification: MC145406 (removed)
Teensy Board Dir TTL side signal
-------- ------ --- ---------- ------
D2 (RXD) <-- 10 (RXD)
D3 (TXD) --> 11 (TXD)
N.C. <-- 12 (CP145) (CTS)
Ground --> 13 (RTS)
Ground --> 15 (DTR)
N.C. <-- 14 (CP148) (DSR)
VCC IC102 left leg pad (near C106)
Overall view of the mod:
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Note that in this case, the teensy is positioned for the picture, normally you have to find a secure spot that would fit in the case. (BTW, I removed the switch because it would become irrelevant & actually confusing and to make space for the teensy board (removed by cutting the 3 legs then pulling it - it was glued to the PCB).The fun part#1: GND
The teensy GND (ground) signal needs to be connected to the "Ground plane". (lots of places to solder on the board). NOTE: the board has a little coating and it might be required to scratch the surface a little to access the metal. #2: 5V
This is the IC102 black square component (TA7805F -- the 5V voltage regulator). Either you find a way to remove it or you just cut the left leg (the one near C106). This is where the 5V needs to be injected. Note that for soldering a wire, you could hook yourself anywhere that trace is going, and in particular on the right leg pad of C107 (near the + sign) or in one of the vias (i.e. the holes).
5v_power.jpgTeensy (viewed from the back):
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At this stage it would be important to test your tablet, the next step is more delicate and thus it would be nice to know that (most of) the board works fine before digging into this.
Essentially with the GND and VCC plugged in (black & red wires in the pictures) plug the teensy USB cable. (start with the small connector on the teensy, then finish with the connector on the computer). The first time you do this is called a "smoke test". If you see your computer powering down instantly, pull the plug right-away, something is badly connected. #4: Remove the MC145406
Best is to use a Dremel to cut all the legs then carefully unsolder all dangling legs on the board without lifting/breaking the "pads" (the pad is the metalic thing on the board where the chip legs are soldered to). If a pad (that is required in the modification) is broken just follow the trace and find another place on the board to solder your wire on.
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The most important serial signals are RXD/TXD (pin 10 and pin 11). The others are either ignored (CTS/DSR) or must be grounded (DTR/RTS).
detail_soldering.jpg#5: Ground DTR and RTS
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These are pin 13 and 15 -- the two bottom yellow wires in the pictures. Now that the MC145406 chip is gone, these are now "floating" (electrically), and should be grounded. This is also important because the UD board might decide to not send any serial data if the floating TTL value decides to go high. Follow the table 2 and the pictures to decide how you are going to do this.
When I say "grounded" I mean connect to the ground (or negative side often seen depicted with the color "black"). There is a lot of "ground" connections on the board -- we call this a ground "plane". It actually covers all the "unused" areas of the PCB.
There are a few holes (called vias) that are big enough to fit a bigger wire gauge. I picked two of them below.
Make sure the other pins (like 16, 14 and 12) are not touching the wires. This is probably one of the most delicate soldering part of this mod.#5: RXD and TXD
These are pin 10 and 11 respectively. Use a longer wire for those as they must go to the Teensy. Check table 2 to know which goes where on the Teensy.
Notice that the MC145406 pads must not be stressed (or they will "lift") so the two wires are held securely by going through a hole at the top of the board (see pictures). You can do it anyway you like, but try to make sure there is (and will be) no stress on the MC145406 pads, these are fragile. EDIT: you cannot use the same holes to secure the wires if you want to re-use the same case since a piece of the actually goes through those holes to "hold" the board. If you remove the power switch there are 2 round holes hidden under it that could serve this purpose as well.
NOTE: if you have 28 gauge wires (smaller than the ones I used for this mod), you can fit the wire in tiny vias (holes) that connects to the pad and solder there. It would typically be more solid as a soldering point (using a smaller wire by itself is more fragile thought if you move it back and forth -- that is a tradeoff).
Soldering tip: position the wire as shown and make sure it is held down in position on top of the pad. Then simply apply the soldering to the wire and it will "fall" to the pad and everything will solder. It does not take much to hold the wire. Make sure there is as little stress as possible on the wire and soldering joint. Plan the wire final shape and position beforehand.#6: Test
Do the same type of test just to be sure nothing major is broken. At this point, it is not expected that the mouse is moving (we need to do the firmware part for this), just that the led blinks when you operate the pen.
Next step is the software (WaxBee) -- see post below.