[Coco] TRS-80 X-Pad

[Gene Heskett]

On Saturday 25 May 2013 12:30:50 Bill Pierce did opine:

> I don't think the Hires adapter could affect the x-pad as it connects
> through the cartridge port. It consists of a cart wired to a pen and a
> pad. Since the whole pad is hard plastic and not some soft, pressure
> sensitive material, the only thing I can figure is the pen and pad are
> electro magnetic, the pen creating magnetic field and the pad's
> "sensors" sending back the location of the pen. The pad can sense when
> the pen is "near" but not "on" the drawing surface. So I would think
> the pad has a magnetic grid of sorts that is equivilent to the
> resolution and could not be modified. I am just assuming here,
> considering the technology of the time (1982) and the construction of
> the unit. No infared, no light sensing, no pressure sensitive. It's all
> solid grey plastic construction except the pen which is metal and looks
> like a ball point pen. here's a link to some pics
> 
> https://sites.google.com/site/dabarnstudio/temp-pics

You are essentially correct about the grid Bill, and to improve the 
resolution one would have to expand the pads surface to make room for 
additional wires in the grid pattern. The probe is an antenna, the circuit 
latches the strongest signal of a scan in both x & y planes  and the pen 
down signal is derived from a contact closure in the probe when the tip is 
pushed back a small amount.  Less than 1/16" IIRC, on mine at least.

I don't recall that there was an os9 driver for it, or even if it came with 
a rsbasic program to exploit it with.  And I haven't had mine plugged in 
for a good 20 years.  I don't believe an OS9 driver for it would be all 
that hard to write, but never seemed to have wanted to play with it given 
the ports data width was only 8 bits, so its max resolution would have been 
255 x 255.  IIRC I looked at the schematic at one time thinking of making 
its data port 16 bits wide, and that wouldn't have been all that difficult 
except there was no room for a piggy backed chip for the higher 8 bits 
within the pad frame height.  So I put it away & haven't pulled it out 
since.

> Bill Pierce
> My Music from the Tandy/Radio Shack Color Computer 2 & 3
> https://sites.google.com/site/dabarnstudio/
> Co-Webmaster of The TRS-80 Color Computer Archive
> http://www.colorcomputerarchive.com/
> Co-Contributor, Co-Editor for CocoPedia
> http://www.cocopedia.com/wiki/index.php/Main_Page
> E-Mail: ooogalapasooo at aol.com
> 
> 
> 
> 
> -----Original Message-----
> From: Richard E. Crislip <rcrislip at neo.rr.com>
> To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
> Sent: Sat, May 25, 2013 10:50 am
> Subject: Re: [Coco] TRS-80 X-Pad
> 
> 
> <SNIP!!> 8-)
> 
> I wonder if the hi-res joystick adaptor would work?

No.
 
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Cheers, Gene
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