[NTLK] Pen Alignment followup

From: Sean Luke (sean_at_cs.gmu.edu)
Date: Tue Mar 05 2002 - 09:45:34 EST

Yesterday I posted stuff indicating that my new Newton was off-kilter of
the pen by several millimeters in the middle of the screen over on one
side, but was fine in the corners. Here's a follow-up.


Deep in the C++ includes in NewtonDev is a C++ header file called
"VirtualMemory.h". In there it has, among other things, a structure
called SGlobalsThatLiveAcrossReboot, which contains, as you might guess,
all the stuff that's guaranteed to stay in memory even through a
reboot. Part of that is:

        // tablet calibration info
        long fTabletValid; // Table data valid
        long fTabletXScale; // Table x scale
        long fTabletXOffset; // Table x offset
        long fTabletYScale; // Table y scale
        long fTabletYOffset; // Table y offset

What this means is that the Newton uses just two variables (scale and
offset) per X or Y dimension. That's pretty bad IMHO, but that's what
it is. Basically when you click on the left "X" during pen alignment,
it stores the (x,y) coordinate where you clicked on (that's the
offsets). Then when you click on the right "X", it computes the scale
from the left "X" to the right "X".

So if things are looking good around the locations where the "X"'s are,
but not good in the middle, there's not a dang thing you can do about it
in software. DANG!

BTW, there is a NewtonScript function called CalibrateTablet() which
calls the pen calibration program (written, it seems, in C++ not
NewtonScript), and returns. There's no other way to calibrate. The
calibration program is the screen with the Newt scribbling on a Newton
that says "Your Newton needs to be calibrated for the way you write..."


I took my new 2100 apart last night but could not figure out how to get
at the screen. It seems to be buried deep underneath a pile of other
stuff, and I couldn't remove that stuff. Has anyone else had experience
getting to the screen layer? How do you do it?


I've discovered another problem with the 2100: the latch is basically
broken -- it doesn't slide shut -- in fact it tries to spring to the
"open" position. I'd also like to get to the screen layer to examine
the latch and see what I can do about it. If nothing else, I will see
if I can swap out the motherboard with my trusty MP2000.


Have you checked the FAQ lately? http://www.guns-media.com/mirrors/newton/faq/
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