A92: Thanks David
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A92: Thanks David
I tried your idea of disabling the interrupts before reading the keypresses.
It works perfectly. Thanks for the help. Also, At one point I tried to
create a custom interrupt for handling the keypresses (so it would all be
done automatically) but it failed. I couldn't get the old interrupt out
and the new one in. It kept crashing and stuff. Maybe you have something
that could help me here. If anyone has any ideas to help please send them.
Thanks
Kebes
>From: David Kühling <dkuehlin@hell1og.be.schule.de>
>Reply-To: assembly-92@lists.ticalc.org
>To: assembly-92@lists.ticalc.org
>Subject: Re: A92: Hi, I have a question too.
>Date: Fri, 05 Nov 1999 13:22:12 +0100
>
>
>Hallo!
>
>I think I know, what caused the problem: When a key is pressed, one of
>the Auto-Ints is triggered periodically 300 times per second. This
>interrupt is in use by the TIOS and checks all the keyboard matrix for
>keypresses (I'm not sure, maybe that auto-interrupt only sets a flag,
>and the 300Hz timer interrupt (another Auto-Int) will do the keyboard
>read). The problem is just, that this keyboard interrupt changes the
>keyboard matrix, which keeps you from reading correctly. So you should
>switch off interrupts before reading.
>You should also consider to use a little longer delay for reading, since
>the required time differs from calculator to calculator and depends
>on the battery power etc. (I figured out that 3 times 'move.l (a7),
>(a7)'
>is sufficient).
>
>Hope this helped.
> David Kühling
>
>Kevin Rees schrieb:
> >
> > I am learning assembly for the 68K. I have been working on writing a
> > library for reading keypresses. It is capable of checking a specified
>key
> > to see if it is held down or not. It returns 1 if the key is held down,
>and
> > 0 if not. I am accomplishing this by writing the row mask of the key to
>be
> > checked to [600018].w pausing briefly (using about 6 NOP instructions)
>and
> > then reading [60001B].b and checking the bit coresponding to the column
>of
> > the key being read. (see LowLevel.txt) I used the same format as is
>used by
> > "Fernando3" for reading the keys. My program works fine except for one
> > little bug. When any key in the same column is pressed (rows 0-6 only)
>the
> > function thinks that the key specified is also pressed. I have been
>working
> > on this for 3 days now, and have now gathered more info. It seems that
>once
> > out of every 2 times that [600018] is written and then [60001B] is read
>it
> > returns the correct result (a byte containing the state of columns 0-7
>in
> > the row specified by the mask)
> > However every 2nd time the port is written and then read it returns a
>byte
> > coresponding to to a seemingly random row between 0 and 6 (Hence the
>problem
> > mentioned earlier). The program that is calling this function is just
>an
> > infinite loop with the key check inside, and a conditional jump out of
>the
> > loop (when the key specified is pressed). it looks something like this:
> >
> > main_loop:
> >
> > move.l <key code>,d0
> > jsr check_key
> > tst.b d0
> > beq exit
> > bra main_loop
> >
> > exit:
> > rts
> >
> > <key code> is a value between 0 and 80 in the format of
> > bit 7 6 5 4 3 2 1 0
> > X X X X X X X X
> > |-----| <- 3 bits (0-7) coresponding to column of key
> > |-------| <- 4 bits coresponding to row of key (0-9)
> >
> > and the check_key function looks something like this
> >
> > movem.l d1-d3,-(a7) ; save registers
> >
> > move.l d0,d1
> > andi.l #7,d1 ; finds column
> >
> > move.w #$FFFF,d2 ; used for row mask
> > lsr.b #3,d0 ; finds row
> > bclr.w d0,d2 ; sets row mask
> >
> > move.w d2,$600018 ; write row mask to I/O
> > nop ; \
> > nop ; \
> > nop ; \ wait for I/O
> > nop ; / to recover
> > nop ; /
> > nop ; /
> > move.b $60001B,d3 ; read I/O
> > not.b d3 ; invert d3
> >
> > btst.b d1,d3 ; test column
> > beq key_not_pressed
> > movem.l (a7)+,d1-d3 ; restore registers
> > move.l #1,d0 ; return 1 if key is pressed
> > rts
> >
> > key_not_pressed:
> > movem.l (a7)+,d1-d3 ; restore registers
> > move.l #0,d0 ; return 0 if key not pressed
> > rts
> >
> > It is pretty simple code, yet it is giving me a huge headache. I have
>found
> > that by repeating the Write and Read section of the code and then doing
>a
> > logical AND on the 2 results, I can get an accurate read on the key
> > specified (hence the conclusion that at least 1 out of 2 reads is
>accurate)
> > but doing so takes extra processor time, and is inconvenient. If any of
>you
> > have any ideas on how I can solve this please let me know.
> >
> > Thanks
> >
> > Kebes
> >
> > ______________________________________________________
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>
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