!!!MOUSE ROUTINE IN AN INTERRUPT
[{TableOfContents }]
General Information
Author: John Maris (prepared by Mathy v. Nisselroy) \\
Assembler: Mac65 \\
Published: MegaMagazine 7 \\
Download: [http://www.mathyvannisselroy.nl/special%20stuff.htm]
PDF: [MOUSE ROUTINE IN AN INTERRUPT/mouse.pdf]
!! Abstract
OK, here is the text that accompanied the mouse routine I posted
on alt.binaries.atari. Unfortunately the original file was self
extracting. So I had to print it out and type it back in. I hope
somebody will read the stuff below and use it in his or her own
program. The text and code where written for the Atari 8 bit,
but the idea should work on other computers too.
~[number] means that there is a small explanation for those not living in the Atari 8 bit world at the bottom of the text.
Mathy van Nisselroy
!! Mouse Routine in an Interrupt
By The Missing Link [1]
In the last years the mouse became very popular, even on Atari
8-bit machines. I've seen a lot of routines, but none of them
were working very good. They took almost all processor time in
the main loop or they were very slow, etc. I talked to your
editor [2] very often about this subject and we were both working
on a better routine. I decided to put my mouse routine into a
Pokey [3] Timer Interrupt....
A few month ago while I was shopping, I got the great idea.
Finally I knew how to do it. I went home, started MAC65 [4],
typed some lines in 10 minutes, and the routine worked great!
The first routine worked in a DLI [5] and VBI [6]. So I knew that
it was possible to put a mouse routine in such an interrupt. I
could even load from disk or play some samples while I was
playing with the mouse. A few days later Freddy [2] visited me
and he was amazed. I showed him my routine and he was surprised
because of the length and the frequency. The routine was short,
very fast and worked very good. You should have seen his face
when I was playing a mouse, while the computer loaded the
directory into the machine....
Later I told to some other programmers about this routine and now
we can see a lot of mouse routines which work in an interrupt.
Most of these routines are still slow or you get a 'flying'
cursor. If you move the mouse too fast, the cursor will move in
reversed direction or will even NOT move. After I had seen these
'f**king' routines I decided to publish my routine on Mega
Magazine [7] with some documentation, so everybody can use a
better mouse routine. I've called it the 'TML Mouse Routine'. The
routine is public domain, but it would be nice if you let me know
(or MegaZine [7]) if you use the routine in one of your products.
It would be nicer if you mention the creator in your programs....
! How the routine works
Depending on the mouse (ST or AMIGA) you will get 4 numbers if
you move the mouse horizontal and 4 other numbers for the
vertical direction. For example: Move the mouse from left to
right and you will get the numbers (STICK(0 or 1) [8] ) 1 2 3 4 1
2 3 4 1 2 3 4 1 2 3 4 etc. (these aren't the right numbers, but
it is only an example). If you read stick(0) twice, you have two
numbers and will know in what direction the mouse moved... If you
get a 1 and a 2, the mouse was moved to the right and if you get
a 2 and a 1, the mouse was moved to the left. You can do the same
thing for the vertical direction.
Now you can create a very big routine with compares, etc., but
that will take a lot of time and you have to check the stick very
often (Freddy did such a routine in the main loop and there was
no time left for any other action), I have made a interrupt
routine which checked the mouse 800 times in a second. This
routine worked like all routines, get a new value from the mouse,
compare it to the old value and do some action. This routine was
also large and didn't work very good. The trick is the use of an
'action table'. Get the old value shift it to the left two times
and add the new value. Now you will have a unique value between 0
and 15. Use this value as index for the table.
An example:
Old value = 2 (shifted 2x makes 8)
New value = 1 (add to 8)
Index value = 9
Earlier I wrote that a 2 and a 1 was a movement to the left, so
we have to decrease the X-pointer. Position 9 will be a 255 in
the index tabel.
Old value = 1 (shifted 2x makes 4)
New value = 2 (add to 4)
Index value = 6
Numbers 1 and 2 is a movement to the right, we have to increase the
X-pointer. We have to put on the sixth position in the index
table a 1.
Conclusion: Now we have only to shift the old value 2 times, add
the new value, use it as index, and add the value we've got to
the X-position. We can do the same for the Y-position. This is a
very fast routine which takes just some time. But still, this is
not the final one....
Sometimes you will get the same value. (old = 1 and new = 1) This
means that there was no mouse action or a very very fast action
in unknown direction. Do nothing, so put 0 in your index table on
position (1+4=5).
The same for 1 and 3. Of course, there must have been some
action, but you can't know what kind of action. It is two steps
if the mouse is moved to the right, but also two steps if the
mouse was moved to the left. So no action on (3+4=7) in your
index table.
The last part was the most important part of this textfile. If
you don't know what kind of action there was, even if you are
sure that there was some action, do nothing! If you do anything
you will get a reversed mouse or a 'flying' one.
On the backside of this disk you will find a pre-screen of my new
texteditor. You can play with it, open some windows, etc., but
that's all. Just an example. You can also find the mouse-source
on this disk. It's in MAC65 [4] format. This one is public
domain. Use it have a lot of fun, as long as you remember that
you took it from this great magazine [7] and remember who wrote
the routine. See you next time!
[#1] John Maris, founder of A.N.G.
[#2] Freddy Offenga, editor of [7]
[#3] Sound chip of the Atari 8bit computer
[#4] MAC65: Assembler software
[#5] DLI: small piece of software that tells the graphics co-processor (ANTIC) in the Atari 8 bit what to do
[#6] VBI: Vertical Blank Interrupt.
[#7] Mega Magazine or just MegaZine: A disk magazine for the Atari 8 bit computer. Seven issues appeared, then they stopped.
[#8] STICK (0) or STICK (1): an Atari BASIC command used to read
joystick ports pins 1 through 4.
For those who wanna look at the code, the PIA, which controls the joysticks in the Atari, is placed at $D300-$D303. Should the source use a different address between $D300 and $D3FF, just substract 4 off this number untill
you get in the above mentioned range. BTW apart from the
occasional SPACE and capital, I changed nothing about this text.
{{{
1000 ;MOUSE ROUTINE IN A DLI
1010 ; MAKE YOUR OWN DL WITH
1020 ;INTERUPT ENABLE, ETC.
1030 ;OR YSE THE INTERUPT IN
1040 ;POKEY TIME INTERUPT!
1050 ;
1060 ;PUBLIC DOMAIN 1994
1070 ;PUBLISHED ON MEGAMAGAZINE
1080 ; POKEY MAGZINE
1090 ; THE BEST OF...
1100 ;
1110 ;WRITTEN BY THE MISSING LINK
1120 ;
1130 ;OLDX = OLD X-VALUE MOUSE
1140 ;OLDY = OLD Y-VALUE MOUSE
1150 ;MXAS = X POSITION FOR CURSOR
1160 ;MMAXX=MAXIMUM X-SCREEN-POS
1170 ;MMAXY=MAXIMUM Y-SCREEN-POS
1180 ;MMINX=MINIMUM X-SCREEN-POS
1190 ;MMINY=MINIMUM Y-SCREEN-POS
1191 ;
1200 ;SET INTERRUPTPOINTER
1210 LDA # <MOUSE
1220 STA 512
1230 LDA # >MOUSE
1240 STA 513
1250 ;INIT MOUSE ROUTINE
1260 JSR MOUSEON
1270 ;INIT VBI ROUTINE FOR CURSOR
1280 LDA #6
1290 LDX # >VBI
1300 LDY # <VBI
1310 JSR $E45C
1320 ;ENDLESS LOOP
1330 DO JMP DO
1340 ;
1350 ;
1360 ;THE MOUSEROUTINE
1370 MOUSE
1380 PHA
1390 TXA
1400 PHA
1410 TYA
1420 PHA
1430 MOUSEA
1440 LDA $D300 ;
1450 LSR A ;MOUSE ON
1460 LSR A ;PORT 1
1470 LSR A ;
1480 LSR A ;
1490 PHA ;SAVE VALUE
1500 AND #3 ;GET X-VALUE
1510 ORA OLDX ;
1520 TAX ;
1530 AND #3 ;MAKE X-INDEX
1540 ASL A ;
1550 ASL A ;
1560 STA OLDX ;SAVE AS OLD
1570 LDY MXAS ;
1580 LDA MOUSETAB,X ;GET TABLE
1590 BMI MOUSY ;ACTION? NO!
1600 BNE MOUSE1 ;YES! DECREASE
1610 MOUSE0
1620 INY ;INCREASE
1630 CPY MMAXX ;MAXIMUM XAS?
1640 BCC MOUSY ;NO, EXIT
1650 MOUSE1
1660 DEY ;DECREASE
1670 CPY MMINX ;MINIMUM XAS?
1680 BCC MOUSE0 ;YES! INCREASE
1690 MOUSY
1700 STY MXAS ;STORE XPOINTER
1710 PLA ;GET MOUSEVALUE
1720 LSR A
1730 LSR A ;SEE THE ROUTINE
1740 AND #3 ;ON THE XAS. IT
1750 ORA OLDY ;IS THE SAME!
1760 TAX
1770 AND #3
1780 ASL A
1790 ASL A
1800 STA OLDY
1810 LDY MYAS
1820 LDA MOUSETAB,X
1830 BMI MOUSEX
1840 BNE MOUSE2
1850 MOUSE1.1
1860 INY
1870 JMP MOUSE3
1880 MOUSE2
1890 DEY
1900 MOUSE3
1910 CPY MMINY
1920 BCC MOUSE1.1
1930 CPY MMAXY
1940 BCS MOUSE2
1950 MOUSEX ; END OF
1960 STY MYAS ;Y-ROUTINE
1970 PLA ;RESTORE
1980 TAY ;A, X & Y
1990 PLA
2000 TAX
2010 PLA
2020 RTI
2030 ;
2040 ;THE Indextable 0=no action
2050 MOUSETAB
2060 .BYTE 255,1,0,255,0,255,255,1,1,255,255,0,255,0,1,255
2070 ;
2080 ;ENABLE DLI
2090 MOUSEON
2100 LDA #192
2110 STA $D40E
2120 RTS
2130 ;DISABLE DLI
2140 MOUSEOFF
2150 LDA #64
2160 STA $D40E
2170 RTS
2180 ;
2190 VBI
2200 ;PUT CURSOR ON SCREEN...
2210 JMP $E45F
2220 ;
2230 ;
}}}