Re: Graphics Tablet...

[mjmahon@aol.com (Michael J. Mahon)]

Jeff Thomas asked:

>I have heard of people making their own "light pens" for Apple II, but
>has anyone ever built a graphics tablet which connects to the joystick
>port?

Light pens for the Apple II series come in two basic flavors: "fast"
pens which connect to a card (either a special card or an 80-column
card), and "slow" pens which connect to the joystick port.

The slow pens are simply a directed CdS photoresistor, whose
changing resistance in response to light can be sensed as a
"paddle" input to the Apple II.  It can be used in conjuction with
software to identify what screen item is being pointed at by
sequentially blinking the screen elements while looking for
a change in the CdS cell resistance.  As you can imagine,
this is pretty slow if there are more than a few things on the
screen, but it can be used satisfactorily to select from a
menu.

Resistive "graphics input devices" were made by Koala and
a few knock-off companies.  These KoalaPad devices are
fairly inexpensive and quite simple.  They should still be
available in the resale markets.  They are used like a
joystick, but are easier to control for drawing.

-michael

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