This is an X-PAD, a pen tablet for the TRS-80 Color Computer (COCO):
It works similar to modern Wacom Tablets and has quite a nice precision and resolution.
This Disk Extended Color Basic (DECB) program from the manual shows how one can do a simple paint app using it.
So the native DECB program is using a bunch of PEEks to pool some memory location for the X, Y coordinates and the pen's pressure (S).
We can PEEK in ugBasic so why not convert this code?
Here it is, I'm creating labels so to keep to the original code structure (numbered lines) but keep in mind this should be re-written to make use of modern basic techniques and controls available on ugBasic. It works both ways though
Code: Select all
SCREEN #14:COLOR #0, #5 :'Set graphic resolution 256x192x2, CSS1
x=0:y=0:s=0:x1=0:y1=0 :'Declare variables: X and Y coords, pressure and older coords values
CLS BLACK :'Clear the screen
LINE 0,8 TO 256,8 :'Draw a top line to split HUD from draw area
subread:
GOSUB xread :'Read tablet coords and pressure
IF s<>3 THEN GOTO subread :'Cycle if pen is hovering
POINT AT(x,y) :'Draw a point on the pen coords
coordcap:
x1=x:y1=y :'Get old pen coords
GOSUB xread :'Read tablet coords and pressure
IF s<>3 THEN GOTO subread :'Return to first cycle if pen is hovering
LINE x1,y1 TO x,y,0 :'Draw a line from old to new coords
GOTO coordcap :'Cycle
xread:
x=PEEK(65376) :'Read tablet coords and pressure
y=PEEK(65377)
s=PEEK(65378)
LOCATE 0,0:PRINT "x=";x;" " :'Print HUD
LOCATE 5,0:PRINT " y=";y;" "
LOCATE 11,0:PRINT " s=";s;
RETURN