76 lines
1.7 KiB
Plaintext
76 lines
1.7 KiB
Plaintext
// SPDX-FileCopyrightText: Chris Pressey, the original author of this work, has dedicated it to the public domain.
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// For more information, please refer to <https://unlicense.org/>
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// SPDX-License-Identifier: Unlicense
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byte joy2 @ $dc00
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word delta
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// Read the joystick and compute the delta it represents
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// in a row-based 40-column grid like the C64's screen.
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define read_stick routine
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inputs joy2
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outputs delta
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trashes a, x, z, n
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{
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ld x, joy2
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ld a, x
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and a, 1 // up
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if z {
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copy $ffd8, delta // -40
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} else {
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ld a, x
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and a, 2 // down
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if z {
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copy word 40, delta
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} else {
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ld a, x
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and a, 4 // left
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if z {
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copy $ffff, delta // -1
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} else {
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ld a, x
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and a, 8 // right
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if z {
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copy word 1, delta
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} else {
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copy word 0, delta
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}
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}
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}
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}
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}
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// You can repeatedly (i.e. as part of actor logic or an IRQ handler)
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// call this routine.
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// Upon return, if carry is set, the button was pressed then released.
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define check_button routine
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inputs joy2
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outputs c
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trashes a, z, n
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static byte button_down : 0
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{
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ld a, button_down
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if z {
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ld a, joy2
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and a, $10
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if z {
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ld a, 1
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st a, button_down
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}
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st off, c
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} else {
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ld a, joy2
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and a, $10
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if not z {
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ld a, 0
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st a, button_down
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st on, c
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} else {
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st off, c
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}
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}
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}
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