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recipes/sms: add controller support

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This commit is contained in:
Virgil Dupras 2019-07-01 15:46:10 -04:00
parent 95fa473641
commit ba2804a255
2 changed files with 63 additions and 22 deletions
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4
recipes/sms/README.md
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@ -28,7 +28,9 @@ The binary produced by the Makefile here has been tested on a Genesis +
[Everdrive MD][everdrive] (I haven't built myself a writable cartridge yet).
It is an adaptation of Maxim's (from SMS power) hello world. I converted it to
ZASM. For now, all it does is show "Hello World".
ZASM. It shows a letter in the range of "a" to "i" depending of which button on
controller A is pressed (only detects one button at once). All buttons of the
genesis controller are supported. Shows "i" when no button is pressed.
I've also added the mandatory "TMR SEGA" header at the end of the binary.

81
recipes/sms/glue.asm
View File

@ -50,34 +50,73 @@ main:
or c
jr nz, .loop2
xor a
out (0xbf), a
ld a, 0x78
out (0xbf), a
ld hl, Message
ld bc, MessageEnd-Message
.loop3:
ld a, (hl)
out (0xbe), a
inc hl
dec bc
ld a, b
or c
jr nz, .loop3
ld a, 0b11000000
out (0xbf), a
ld a, 0x81
out (0xbf), a
.loop4:
jr .loop4
ld b, 0x41
jr updateLetter
mainloop:
; What we do here is simple. We go though all bits of port A controller
; increasing B each time. As soon as we get a hit, we display that
; letter. Pressed buttons go low.
; This logic below is for the Genesis controller, which is modal. TH is
; an output pin that swiches the meaning of TL and TR. When TH is high
; (unselected), TL = Button B and TR = Button C. When TH is low
; (selected), TL = Button A and TR = Start.
ld a, 0b11111101 ; TH output, unselected
out (0x3f), a
ld b, 0x41 ; a
in a, (0xdc) ; I/O port
and 0b00100000 ; Port A Button C pressed
jr z, updateLetter
inc b ; b
in a, (0xdc)
and 0b00010000 ; Port A Button B pressed
jr z, updateLetter
inc b ; c
in a, (0xdc)
and 0b00001000 ; Port A Right pressed
jr z, updateLetter
inc b ; d
in a, (0xdc)
and 0b00000100 ; Port A Left pressed
jr z, updateLetter
inc b ; e
in a, (0xdc)
and 0b00000010 ; Port A Down pressed
jr z, updateLetter
inc b ; f
in a, (0xdc)
and 0b00000001 ; Port A Up pressed
jr z, updateLetter
ld a, 0b11011101 ; TH output, unselected
out (0x3f), a
inc b ; g
in a, (0xdc)
and 0b00100000 ; Port A Start pressed
jr z, updateLetter
inc b ; h
in a, (0xdc)
and 0b00010000 ; Port A Button A pressed
jr z, updateLetter
inc b ; i
; no button pressed on port A, continue to updateLetter
; Prints letter in B
updateLetter:
xor a
out (0xbf), a
ld a, 0x78
out (0xbf), a
ld a, b
out (0xbe), a
jr mainloop
Message:
.dw 0x28,0x45,0x4c,0x4c,0x4f,0x00,0x37,0x4f,0x52,0x4c,0x44,0x01
MessageEnd:
PaletteData:
.db 0x00,0x3f