(please tell me where I made typos, I am sure I made some )

With my recent work on TinyCraft, people have been asking me how I make my grayscale so beautiful. So here is a tutorial!
(what do you mean by "you stole thepenguin's sentence" ? )

So one day, I read thepenguin's tutorial to see if I could get something to work in Axe on a 83+BE without Full speed and I understood that I had to refresh the screen 50-60 times per second.

Now, How would you do this in Axe ? With a loop that runs exactly at 50 Hz ? Not really, for two reasons:
- maybe your calc will have beautiful grey at 50 Hz but others may hae it beautiful at 52 Hz
- maybe the loop will run at 50 Hz on your calc but will run at 48 Hz on others

So you need interrupts. If you don't know how interrupts work, check out Hot Dog's tutorial.
Problem: the slowest interrupts still runs at a higher frequency than 100 Hz, there is no interrupt at 50 Hz. But who told you that the screen was actually refreshed every time the interrupt runs ?

The speeds for the interrupts are as follow (according to Hot Dog):

Speed // 83+ // 84+
0 // 560 Hz // 512 Hz
2 // 248 Hz // 228 Hz
4 // 170 Hz // 146 Hz
6 // 118 Hz // 108 Hz

So:
-with speed 0, we would need to refresh the screen only 1 time every ten runs, because 50<560/10<60
-with speed 6, we would need to refresh the screen only 1 time every 2 runs, because 50<118/2<60
-etc

Let's make a try with speed 0 for example. Then, it will be easy to get it to work with arbitrary speeds
So for educationnal reasons, we are going to make a stupid and unoptimized program that will include beautiful grey. Note that I don't code so bad in real life
Let's draw for example two rectangles, one black, the other one grey.

.AA
ClrDraw^rr
Rect(0,0,8,8,L3)
Rect(0,8,8,8,L6)

Now we need to set up the interrupt. We use speed 0 so we need to refresh the screen 1 time every 10 runs. We need a counter that will tell the calculator if it should refresh or not. So the routine used as an interrupt should look like this.

Lbl DG
T+1?T
If T=10
 0?T
 DispGraph^r
End
Return

Another solution would be this one

Lbl DG
T+1?T
!If T^10
 DispGraph^r
End
Return

And now, the only thing we need is to set this interrupt on to refresh the screen automatically

.AA
FnOff
ClrDraw^rr
Rect(0,0,8,8,L3)
Rect(0,8,8,8,L6)
0?T
fnInt(DG,0)
Repeat getKey(0)
End
LnReg
Return

Lbl DG
T+1?T
!If T^10
 DispGraph^r
End
Return

If you want a little more optimised version of this, here it is

.AA
FnOff
ClrDraw^rr
Rect(0,,8,,L3)
Rect(0?T,8,,,L6)
fnInt(DG,0)
While 1
EndIf getKey(0)
LnReg
Return

Lbl DG
!If T++^10
 DispGraph^r
End
Return

If you want a faster-than-light or a smaller-than-0-bytes version of this, ask Runer112.

Now, the only thing that is missing in that tutorial is "how to make a calibration screen ?", but I am sure you can do this without my help. You just need to make a menu that will select between 4 values and each value gives an interupt speed and a timer-max.

Notes:
I made an example with 3 levels of grey but it works with 4 levels too
See TinyCraft for example.

Disadvantages of this method:
-First of all, the screen is automatically refreshed. This means two bad things: this will make you forget your good habit to make "DispGraph"s inside your loops, and sometimes, you only want to refresh after it cleared all and redraw all, but now you can't choose anymore where the refreshing will happen
-For some reason, using the Text() command on a regular 83+ (not SE) kills the interrupt (but everything else in the program runs fine). To avoid problems, you can use Jacobly's TEXT Axiom or simply avoid the Text() command when the interrupt is running (disable it before using Text() then put it back for example, or prerender all the text in your menus instead of putting the Text() commands in the loop).

If you can match that with axe, I'll be impressed

I get exactly this on both my 83+BE (with interrupt 4) and my 84+SE (with interrupt 0), with just the little "scrolling glitch line", as you say
However, the grey is not that perfect on my sister's calc, whatever the interrupt I choose

edit: here is what I get with Wabbitemu set at 68 Hz and 5 shades with this program
.AA
FnOff
ClrDraw^rr
Fill(L3+252,252,255)
Fill(L6+252+252,252,255)
fnInt(DG,0)
Pause 200
While 1
EndIf getKey(0)
LnReg
Return

Lbl DG
!If T++^10
 DispGraph^r
End
Return

here is what I get with Wabbitemu set at 68 Hz and 5 shades with this program

That counts, I'm impressed.

I guess i have a unlucky calc then, coz greyscale never really worked out for me

Necropost.

!If T++^10

Why don't you just do DS(T,10) ?

Anyway this method is awesome, but smooth scrolling a tilemap with 4 level gray looks crappy. I'll stick with three.

Or maybe I'm just scrolling too fast. Syncing scrolling to LCD updates with While and Stop actually makes it looks a lot better. But also incredibly slow. :S

No, Axe only draws once each frame, but four frames for each full "greyscale loop." Of course, that hardly matters in an interrupt.

How would you go about allowing moving objects on the screen with the interrupt running?  Would you have to somehow sync the refresh rate with the amount of frames? (Sorry if I worded that incorrectly)