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Joined: 13 Apr 2009
Posts: 4

Posted: 22 Jun 2010 02:38:12 pm    Post subject:

Hey there!

I recently discovered a little exploit on the TI 84+. With the contrast set to 4 I ran this program:


Now I won't try to explain it because the forum on TI|BD shows that a linguistic explanation is rather confusing. You can of course read ithere but you better just follow these steps:

1.write the program it
3.move the cursor in the graph screen around and notice some strange effects on the overlapping elements of the cursor and the pixels just drawn. What you should see is that the just drawn pixels are grey and that the cursor on some points is black!
I have no funded clue how this works or why but I do suspect it is a hardware 'fault'. When you make the step in the for loop 1 or >2 it will not work. Now, if indeed this is a hardware fault then maybe this can be further used in assembly language to make greyscale without having to turn pixels on and off that fast...
In fact the intensity of the pixel is determined by the amount of power on the cathode (or anode) of a certain pixel. If this somehow someway can be regulated (maybe we can figure out how by exploring this exploit further) then greyscale is so much easier and less CPU intensive!

The last part is merely an assumption I do not claim anything to be true of it but I have my suspicions based on my megre asm experience...(notice that I put it in the basic section because the program causing this is in basic however, further discussion about this may be going more in the direction of asm programming, I leave it to the moderators to decide the proper place for this topic)
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Joined: 09 Aug 2009
Posts: 207

Posted: 22 Jun 2010 08:17:13 pm    Post subject:

As mentioned, we are already aware of this. Note that this is not the driver, but rather the display itself. Certain patterns (like the one you have, and alternating columns) cause the LCD to display those pixels with less power. The main thing to do, then, is to see which patterns produce this graying out, and how, and then to see if those patterns are at all useful. Maybe someone else has more info on the LCD and what types of patterns cause this to occur?
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Active Member

Joined: 29 Aug 2008
Posts: 565

Posted: 23 Jun 2010 03:28:06 am    Post subject:

On a "normal" contrast of 5 I noted some strange grey lines appearing but I forgot them over some time.

It is quite funny to see those effects. It also happens some interesting effects in higher contrasts like 6.
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Joined: 13 Apr 2009
Posts: 4

Posted: 23 Jun 2010 02:23:33 pm    Post subject:

Well basicaly this is the greyscale version of something that is extremely obvious. Sometimes on the homescreen I get strange lines that 'sore' through my equations or expressions. They just darkne or lighten parts that are not "blocked" by other text. This happens most in HomeScreen based games. I still think it must be the driver cause the driver litterlay decides which lines are powered. The screen itself can never cause this albeit it can lose power somehow somewhere.

it reamains intresting, maybe we should list all of the discovered events that trigger this type of greyscale to occur?
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Active Member

Joined: 24 May 2006
Posts: 693

Posted: 24 Jun 2010 12:42:48 am    Post subject:

I've noticed these, never knew the reason why though. Razz

Last edited by Guest on 24 Jun 2010 12:42:57 am; edited 1 time in total
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