** ** ** ** ** ** ** ** ** ** ** **¢ Modifying The Super Sketch¢ Make the Graphics Tablet¢ Koala-Compatible¢ by Thomas J. Andrews, member of the¢ OL' HACKERS N.Y.¢¢ PART A¢¢ A while ago I set out to find a¢ good graphics processor so I could¢ draw pictures of vegetables to use¢ with signs for our roadside vegetable¢ stand. I tried several programs and¢ input devices, with varying results.¢ (See Current Notes, May/June 1995, for¢ an in-depth article on those¢ results.)¢ One of the devices I used was the¢ Super Sketch Graphics Tablet, sold by¢ More Than Games of Austin, Texas. ¢ This tablet is not a touch pad like¢ the Koala, but features a movable arm¢ that can be used to trace pictures and¢ drawings. It comes with its own¢ software cartridge, and seems quite¢ well-made for a device of this type.¢¢ The Problems¢ It's not without its problems,¢ however. (What isn't?) The Super¢ Sketch is almost, but not quite¢ compatible with the Koala Pad. ¢ Consequently, it doesn't work as well¢ as it might with some graphics¢ processors. It does work with¢ Rambrandt 2.0, only partially with¢ Micro Illustrator, and not at all with¢ Pixel Artist Deluxe. It will work¢ with the Print Shop Graphics Editor,¢ but with the Print Shop Companion¢ Editors the vertical axis is reversed,¢ that is, down on the tablet is up on¢ the screen.¢ This limits the tablet's¢ usefulness all by itself, but there¢ are problems with the software, too. ¢ Although I can't confirm it from¢ personal experience, since I don't¢ have the hardware involved, I've heard¢ reports that the cartridge won't work¢ with XL's with the Computer Software¢ Services OS modification. Even if the¢ software DOES work, the drawings are¢ saved in a proprietary format,¢ incompatible with the more¢ "established" formats.¢¢ The Solutions¢ Help is on the way, though, and¢ it's right here. First, the format¢ problem. There is a program called¢ "Graphics Transformer" that was¢ produced by Alpha Systems several¢ years back. I don't know if it's¢ still available commercially - I got¢ mine on the "pre-owned" market. Among¢ others, it will convert Super Sketch¢ files into a variety of formats,¢ including Micro Illustrator and Micro¢ Painter. It works well, and is fairly¢ easy to use.¢ For those who don't have¢ RAMbrandt 2.0, a recent ad in Atari¢ Classics indicates that B&C¢ Computervisions now carries it, at a¢ price of $17.95. Their address is¢ 1725 De La Cruz Blvd.#7, Santa Clara,¢ CA 95050-3011. Anybody who is serious¢ about drawing with the 8-bit should¢ consider this program.¢ I can't do anything about the¢ problem with the CSS-modified machines¢ (OS Plus). I'm not sure what's going¢ on there, and I don't have the¢ hardware to find out. I wish I did.¢¢ Koala Compatibility¢ We CAN do something about the¢ Koala compatibility problem. In fact,¢ that's what this article is really¢ about.¢ The working area of the Super¢ Sketch's arm corrisponds closely to¢ that of the Koala Pad, and two of the¢ four switches corrispond to the Koala¢ switches. The SELECT switch is the¢ same as the Koala left switch, and the¢ left-hand LIFT switch is the same as¢ the Koala right switch. The problem¢ is that there is no position of the¢ arm that corrisponds to the Koala with¢ the stylus raised from the pad. As¢ harware hacks go, it's pretty simple¢ to fix this.¢ The Super Sketch and Koala Pad¢ each use the PADDLE functions to¢ report the position of the arm or¢ stylus. When the stylus is lifted on¢ the Koala, both PADDLE functions will¢ read a low number, somewhere around 3.¢ There is no position on the Super¢ Sketch that will give that combination¢ of readings, so we have to install a¢ switchable bypass that will.¢¢ You'll need the following items:¢¢ A mini SPST switch. The style is¢ up to you, but I'd recommend either a¢ slide or rocker switch. Most toggle¢ switches stick up too high, push-¢ button on/off types wear out too¢ quickly, and rotary switches would be¢ awkward and a bit bulky. Don't use a¢ momentary switch. Size is important. ¢ Too large will limit your positioning¢ options, and too small will be hard to¢ use. A SPDT, DPST, or DPDT switch can¢ be substituted, if that's what you¢ happen to have.¢ Two (2) diodes. The selection here¢ is not particularly critical. I used¢ 1N914's because I happened to have¢ them on hand. You can get a package¢ of 10 of them from Radio Shack for¢ around $1.20.¢ Some light, flexible insulated¢ wire. This needs to be light and¢ flexible because some of it will be¢ moving around with the arm. I used¢ some wire salvaged from an old¢ joystick cable. Color coding would be¢ nice and professional-looking, but¢ isn't absolutely necessary.¢ A drill and bit the correct size to¢ mount the switch.¢ A thermal glue gun and some glue.¢ Philips head screwdriver.¢ Needle nose pliers.¢ Low-wattage electronics soldering¢ iron and some electronics solder.¢¢ Disassembly¢ First, I should warn you that¢ this procedure will void any warranty¢ you may have on your Super Sketch. ¢ This may not be a problem, since PPI,¢ the maker of Super Sketch, doesn't¢ seem to exist any more. Rick¢ Detlefsen of More Than Games may¢ provide some sort of short-term¢ warranty, but I'm sure it won't cover¢ this sort of modification.¢ That said, remove each of the¢ four switch caps by lifting straight¢ up. Now turn the Super Sketch over¢ and remove the four Philips head¢ screws. If your tablet is like mine,¢ one of the screws will want to stay in¢ the hole because of a cardboard¢ retainer. It isn't necessary to¢ remove that screw from the base; just¢ back it out of the top. Don't let the¢ top drop off just yet.¢ Flip the tablet back over and¢ lift off the top. Now, before further¢ disassembly, is the time for a little¢ investigation. Look the mechanism¢ over carefully. Move the arm around¢ (but DON'T lift it) and observe what¢ happens inside. Look for a convenient¢ place to mount your switch where it¢ couldn't possibly interfere with the¢ mechanism. Just where that will be¢ will depend on a lot of things - the¢ size of the switch, whether you're¢ right- or left- handed, and your¢ personal preferences.¢ Once you've decided, drill the¢ hole(s) and temporarally mount the¢ switch. Set the top back into place¢ and check once again for freedom of¢ arm movement. If necessary, adjust¢ the placement of the switch. When¢ satisfied, remove the top again and¢ unmount the switch.¢ Remove the paper clamp next. ¢ It's held in place by two light-¢ colored tabs on either side. Take¢ your needle nose pliers and GENTLY¢ squeeze each pair together just far¢ enough to release the clamp. Lift it¢ off and set it to one side. There are¢ two coil springs underneath it. Put¢ them to one side, too.¢ Lift the arm straight up, taking¢ note of how it connects to the¢ mechanism underneath. Put it with the¢ paper clamp. Lift the remaining¢ smoke-colored flat piece of plastic¢ off the retaining pins and put it with¢ the other parts.¢¢ The Modifications¢ Now you're finally down to the¢ business area of the Super Sketch. ¢ Notice the two long, narrow metallic¢ parts. These are POTENTIOMETERS¢ (POTs, for short). They're the parts¢ that report the arm's position to the¢ computer, and they are what we have to¢ bypass with the switch. One of them¢ is for the horizontal coordinate; the¢ other is for the vertical. The¢ vertical is the one mounted in the¢ movable T-shaped plastic piece.¢ Look at the wires fastened to the¢ pots, taking note of how they're¢ routed and where they're secured with¢ a dollop of thermal glue. You'll want¢ to use a similar routing for the wires¢ you're going to install.¢ It's time to start hacking, so¢ fire up that soldering iron. While¢ it's warming, look at the pots again¢ and locate the wire on each one that¢ is the same color. (On mine it was¢ purple.) This is the +5 volts supply¢ line. Cut a piece of wire (use the¢ same color, to look professional) a¢ little longer than long enough to go¢ from the terminal for this wire on the¢ stationary pot to the new switch and¢ strip 1/4 inch of insulation from each¢ end. Carefully solder one end to the¢ pot terminal and route the wire to¢ where the switch will be. Don't¢ secure it yet. Solder the other end¢ to one terminal of the switch. (If¢ using a DT switch, solder to the¢ center terminal.)¢ Cut another piece of wire to go¢ from the other terminal of the pot to¢ the switch, strip the ends, and solder¢ to the pot terminal ONLY. Do the same¢ for the terminal on the movable pot ¢ that is NOT the same color as one on¢ the stationary pot. (Mine was green.) ¢ Be sure to have enough extra on that¢ one to allow freedom of movement.¢ We'll need to connect a diode¢ somewhere in each of these last two¢ lines between the pots and the switch.¢ A diode is a solid state device that¢ essentially allows current to flow¢ through it in only one direction. It¢ has low resistance in that direction,¢ called the FORWARD resistance, and a¢ high resistance in the other, the¢ REVERSE.¢ The diodes will perform two¢ functions.¢ First, the forward resistance is¢ just right to provide the PADDLE¢ readings we're looking for. ¢ Second, the reverse resistance¢ prevents the pots from interfering¢ with each other when the switch is¢ "OFF".¢ Every diode has an indication on¢ it as to which end "stops" current¢ flow. This end is called the CATHODE. ¢ If you're using the 1N914, you'll see¢ a dark band painted on one end. Other¢ diodes may use the shape of the case -¢ one end will be rounded; the other¢ squared off. The squared-off end is¢ the cathode.¢ You can install the diodes nearly¢ anywhere along the wires from the pots¢ that you haven't connected to the¢ switch yet. Try to select positions¢ where the diodes can't posibly touch¢ each other. You'll be securing the¢ wire from the moving pot with thermal¢ glue in the same place the original¢ wires are, so don't put that diode in¢ the area where the wire will be doing¢ a lot of flexing, unless you want it¢ to eventually break off.¢ Wherever you decide to put them,¢ cut the wires and strip the ends. ¢ Solder one diode to each wire with the¢ cathode toward the pot. Be careful¢ with the heat here; use only enough to¢ make a good joint. Too much will ruin¢ the diode.¢ Solder a wire to the other end of¢ each diode. Then, solder the other¢ ends of both wires to the unused¢ switch terminal. (On a DPDT switch,¢ use one of the terminals in the row of¢ three where you soldered the first¢ switch wire. DON'T use the other row¢ of three.)¢¢ Use the thermal glue to secure¢ the wires into place. The spots where¢ the original wiring was secured are¢ good places. but you can use more if¢ you need them. Be sure to put a¢ dollop of glue on each side of each¢ diode.¢¢ Testing¢ Take this "assembly" to your¢ computer and plug it into joystick¢ port #1. Boot up with BASIC and type¢ in the following line:¢¢ 10 ? PADDLE(0),PADDLE(1):GOTO 10¢ Then type RUN. Work the newly¢ installed switch and watch what¢ happens to the readings on the screen.¢ With the switch ON, you should get¢ readings of 1 or 2 from both PADDLES. ¢ Try moving the T and the slide on the¢ vertical pot both with the switch ON¢ and OFF. With it ON, there should be¢ no effect. With it OFF, movement of¢ one pot shouldn't affect the readings¢ of the other.¢ If it doesn't work correctly,¢ look over your work for mistakes. ¢ Things to look for are diodes¢ installed in reverse direction, diodes¢ blown by too much heat, shorted switch¢ terminals, and bare wires touching¢ each other.¢¢ Reassembly¢ Once everything is working¢ correctly, it's time to reassemble the¢ tablet. First, make sure the slide¢ for the stationary pot rests in its¢ notch in the plastic T. Then, replace¢ the flat piece of plastic, taking care¢ to locate the pins in the proper¢ holes.¢ The arm is next. Put the metal¢ pin into the hole in the vertical¢ pot's slide, then maneuver the arm¢ until the pivot circle will drop into¢ place. Move the arm around to make¢ sure both pot slides move freely.¢ Place the two paper clamp springs¢ over the retaining pins on the base¢ plate. Lay the clamp into place,¢ locating the other ends of the springs¢ in the retaining pins on it. GENTLY¢ push the clamp over the locking tabs,¢ one side at a time, until it snaps¢ into place. Don't use too much force,¢ or you'll break them.¢ ¢ (See Part B on this OL HACKERS SEPT/¢ OCT, 1995 newsletter!)¢ ***
