keyboard reset

[geldo79]

Hi,


i have the possibility in my game to pause it by pressing p using the following code:


Check_key:


move.b $bfec01,d0

not.b d0

ror.b #1,d0

cmp.b #$19,d0

.
.
.
bset #6,bfee01

rts



In my main loop, i use



bclr #6,$bfee01


for the handshake. Everything works fine. But there is one problem. When the game ends and i get back to the title screen, i can press p, and when i start a new game, it starts in pause mode. Think its because $bfec01 is also written to in my title screen. Is there a possibility to reset $bfec01 when my game starts, so that it does not recognize a key press during the title screen?


Greetings
Christian

[phx]

More information needed.

Switching the SP back to input by clearing bit 6 of CIA-A CRA ends the handshake. But I see nothing which initiates the handshake and waits long enough.

Usually you want to handle your key presses via an interrupt handler. If you neither took over the system nor registered a proper interrupt handler with AmigaOS there will be more complications, because the OS keyboard handler may be still active.

[geldo79]

I extracted the relevant parts. This is what it looks like.

        jsr	-$78(a6)		   ; close Workbench
	jsr	-$132(a6)		   ; Disable Multitasking
        .
        .
        .

main_loop:

        move.l        $dff004,d0
        and.l         #$1ff00,d0
        cmp.l         #240<<8,d0
        bne.w         main_loop
        bsr.w         Check_Key
        .
        .
        .
        Here all the calculations for the frame
        .
        .
        .
	
GamePause:

	cmpi.w        #0,PauseGame
	beq.w         noGamePause
	bclr          #6,$bfee01
	
VSync_pause:

	cmpi.b        #$ff,$dff006
	bne.w         VSync_pause
	bsr.w         Check_Key
	bra           GamePause	

noGamePause:
	
	bclr          #6,$bfee01
	bra           main_loop
	
******************************
	
Check_Key:

	move.b        $bfec01,d0      
	not.b         d0
	ror.b         #1,d0          
	cmp.b         #$19,d0         
	beq           PKeyPress
	bra           keyreset
	
PKeyPress:
	
	cmpi.w        #0,ppressed
	bgt.w         Check_Key_End
	cmpi.w        #0,PauseGame
	bgt.w         PKeyPress_Reset
	move.w        #1,PauseGame
	move.w        #1,ppressed
	bra            Check_Key_End
	
PKeyPress_Reset:
	
	move.w        #0,PauseGame
	move.w        #1,ppressed
	bra           Check_Key_End
	
keyreset:
	move.w        #0,ppressed

Check_Key_End:

	bset          #6,$bfee01
	rts
	
**********************************

PauseGame:
	dc.w    0
	
ppressed:
	dc.w    0

[a/b]

Forbid() is -132 (decimal), -$132 is SetSignal().

OK, looking at the code.. Handshake is not done properly. You start a handshake (bset #6) at the end of Check_key, and then immediately finish it (bclr #6) without waiting.

[geldo79]

Originally Posted by a/b

Forbid() is -132 (decimal), -$132 is SetSignal().

Aahhh! I never disabled multitasking?!

Originally Posted by a/b

OK, looking at the code.. Handshake is not done properly. You start a handshake (bset #6) at the end of Check_key, and then immediately finish it (bclr #6) without waiting.

Ok....but there's a lot of code in between, that is not shown here. Maybe this does the waiting. I Edited the code above. In fact it works.

[a/b]

Well, a 68040/060 can eat a lot of code for breakfast ;p. Let me check, so i don't mix up CIA timer value and actual time... HRM says at least 85 microsec. For comparison, one rasterline in PAL mode is approx. 64 microsec.
But if you have a lot of stuff in between, yeah then it should work.

While we are at it, consider using sf (set false) and st (set true) instead of move #0/1, and then tst.b instead of cmp #0/1 if you only need a true/false flag.

[phx]

Forbid() does not disable interrupts. Which means the input.device interrupt-handler for the keyboard is still running in parallel to your code.

Also, the handshaking is still wrong.
After reading the keycode from the CIA-A serial port you should initiate handshaking by driving the SP as output (set bit 6 of CRA), then after 85us back to input (clear bit 6 of CRA).

Probably your keyboard code only works (most of the time, when typing slowly) because the OS interrupt handler is still running and does the handshaking for you. You only read the last state of the SDR.

Solution: Take over the system or use the OS.

[a/b]

-$78(a6) = -120(a6) is Disable(), so that part is covered but the comment is 'slightly' deceiving :P.
Looking at the edited code, phx is right. Once you pause (go to the VSync_pause branch), you call Check_Key and then immediately loop back to GamePause, which does bclr #6 without a delay (because now there's no all the extra stuff you normally do that would delay it).

[phx]

Originally Posted by a/b

-$78(a6) = -120(a6) is Disable(), so that part is covered but the comment is 'slightly' deceiving :P.

Indeed, you may be right! I am not that familiar with LVOs in hexadecimal notation.
But then the wrong Forbid() shouldn't matter.

It's also hard to determine actual key-presses without checking for interrupts. If you don't want to establish a keyboard interrupt handler, then I would at least check bit 3 of the ICR whether an SP-interrupt happened (indicating a new key code transmitted by the keyboard). Only then read the SDR and do the handshaking.

[geldo79]

Ok. But to get back to the main issue (the Keyboard reading works in my main loop...maybe i can make it better anyway). But as i wrote above, when i leave the main loop at the end of a game and get back to the title screen (which is another loop where i do not explicitly read the Keyboard), press then "p" anyway, and start a new game afterwards, it immediately jumps into the pause loop. Thus, the key reading is being executed in my title loop, and leads to the game pause when started. Any ideas how to prevent the key reading in the title loop?

[a/b]

Then you should flush any buffered keystrokes (basically, keep reading as long as you're getting keycodes from the keyboard and discard them) before starting to accept new ones.

[geldo79]

But how can i discard them? I thought $bfec01 keeps the last pressed key. Seems that i can not reset it.

[paraj]

Originally Posted by geldo79

But how can i discard them? I thought $bfec01 keeps the last pressed key. Seems that i can not reset it.

Really, you should implement better keyboard handling like already suggested. But as a quickish fix just read the keyboard on the title screen (ignoring the result) and clear the pause related flags before starting.


The CIA SDR register where you're reading the key from isn't an instantaneous value representing what key is currently pressed, but rather a buffer of the last key event (both up and down). If you don't process a key event it'll stay there.

[geldo79]

That works. I just call Check_key in my title screen loop now, and reset the pause flags when starting a new game. Thanks a lot.