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Amiga ACS 1998 #6
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l.asm
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Assembly Source File
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1998-06-08
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4KB
|
144 lines
;THE COMPUTER CODE CONTAINED HEREIN IS THE SOLE PROPERTY OF PARALLAX
;SOFTWARE CORPORATION ("PARALLAX"). PARALLAX, IN DISTRIBUTING THE CODE TO
;END-USERS, AND SUBJECT TO ALL OF THE TERMS AND CONDITIONS HEREIN, GRANTS A
;ROYALTY-FREE, PERPETUAL LICENSE TO SUCH END-USERS FOR USE BY SUCH END-USERS
;IN USING, DISPLAYING, AND CREATING DERIVATIVE WORKS THEREOF, SO LONG AS
;SUCH USE, DISPLAY OR CREATION IS FOR NON-COMMERCIAL, ROYALTY OR REVENUE
;FREE PURPOSES. IN NO EVENT SHALL THE END-USER USE THE COMPUTER CODE
;CONTAINED HEREIN FOR REVENUE-BEARING PURPOSES. THE END-USER UNDERSTANDS
;AND AGREES TO THE TERMS HEREIN AND ACCEPTS THE SAME BY USE OF THIS FILE.
;COPYRIGHT 1993-1998 PARALLAX SOFTWARE CORPORATION. ALL RIGHTS RESERVED.
PUBLIC joy_read_stick_friendly_
joy_read_stick_friendly_:
; ebx = read mask
; edi = pointer to event buffer
; ecx = timeout value
; returns in eax the number of events
mov RetryCount, 0
mov _joy_bogus_reading, 0
joy_read_stick_friendly_retry:
inc RetryCount
cmp RetryCount, 3
jbe @f
mov _joy_bogus_reading, 1
inc _joy_retries
mov eax, 0
ret
@@:
push ecx
push ebx
push edi
and ebx, 01111b ; Make sure we only check the right values
; number of events we found will be in bh, so this also clears it to zero.
mov dx, JOY_PORT
cli ; disable interrupts while reading time...
call joy_get_timer ; Returns counter in EAX
sti ; enable interrupts after reading time...
mov LastTick, eax
waitforstable: in al, dx
and al, bl
jz ready ; Wait for the port in question to be done reading...
cli ; disable interrupts while reading time...
call joy_get_timer ; Returns counter in EAX
sti ; enable interrupts after reading time...
xchg eax, LastTick
cmp eax, LastTick
jb @f
sub eax, LastTick
@@: ; Higher...
add TotalTicks, eax
cmp TotalTicks, ecx ; Timeout at 1/200'th of a second
jae ready
jmp waitforstable
ready:
cli
mov al, 0ffh
out dx, al ; Start joystick a readin'
call joy_get_timer ; Returns counter in EAX
mov LastTick, eax
mov TotalTicks, 0
mov [edi], eax ; Store initial count
add edi, 4
again: in al, dx ; Read Joystick port
not al
and al, bl ; Mask off channels we don't want to read
jnz flip ; See if any of the channels flipped
; none flipped -- check any interrupts...
mov al, 0Ah
out 20h, al
in al, 20h ; Get interrupts pending
cmp al, 0
je NoInts
; Need to do an interrupt
sti
nop ; let the interrupt go on...
cli
; See if any axis turned
in al, dx
not al
and al, bl
jz NoInts
; At this point, an interrupt occured, making one or more
; of the axis values bogus. So, we will restart this process...
pop edi
pop ebx
pop ecx
jmp joy_read_stick_friendly_retry
NoInts:
call joy_get_timer ; Returns counter in EAX
xchg eax, LastTick
cmp eax, LastTick
jb @f
sub eax, LastTick
@@: ; Higher...
add TotalTicks, eax
cmp TotalTicks, ecx ; Timeout at 1/200'th of a second
jae timedout
jmp again
flip: and eax, 01111b ; Only care about axis values
mov [edi], eax ; Record what channel(s) flipped
add edi, 4
xor bl, al ; Unmark the channels that just tripped
call joy_get_timer ; Returns counter in EAX
mov [edi], eax ; Record the time this channel flipped
add edi, 4
inc bh ; Increment number of events
cmp bl, 0
jne again ; If there are more channels to read, keep looping
timedout:
sti
movzx eax, bh ; Return number of events
pop edi
pop ebx
pop ecx
ret