** ** ** ** ** ** ** ** **  **  **  **›         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!)›               ***