aboutsummaryrefslogtreecommitdiff
path: root/tests/src/shared/joypad.s
diff options
context:
space:
mode:
Diffstat (limited to 'tests/src/shared/joypad.s')
-rw-r--r--tests/src/shared/joypad.s86
1 files changed, 0 insertions, 86 deletions
diff --git a/tests/src/shared/joypad.s b/tests/src/shared/joypad.s
deleted file mode 100644
index afd0a68..0000000
--- a/tests/src/shared/joypad.s
+++ /dev/null
@@ -1,86 +0,0 @@
-;; Taken from https://github.com/mssola/code.nes.
-
-.scope Joypad
- ;; Button masks.
- BUTTON_A = 1 << 7
- BUTTON_B = 1 << 6
- BUTTON_SELECT = 1 << 5
- BUTTON_START = 1 << 4
- BUTTON_UP = 1 << 3
- BUTTON_DOWN = 1 << 2
- BUTTON_LEFT = 1 << 1
- BUTTON_RIGHT = 1 << 0
-
- ;; Port addresses for controllers.
- JOYPAD1 = $4016
- JOYPAD2 = $4017
-
- ;; After running a `joypad_read_*` function these two variables will contain
- ;; the given result.
- m_buttons1 = $22
- m_buttons2 = $23
-.endscope
-
-;;;
-;; Read the first joypad. This method is fast but it might be vulnerable to the
-;; DPCM bug (see: https://www.nesdev.org/wiki/Controller_reading_code).
-joypad_unsafe_read:
- ldx #$00
- ;; NOTE: fallthrough
-
-;;;
-;; Read the joypad as indexed by the X register (0 for controller 1; 1 for
-;; controller 2). This method is fast but it might be vulnerable to the DPCM bug
-;; (see: https://www.nesdev.org/wiki/Controller_reading_code).
-joypad_unsafe_read_x:
- ;; Start the latch process.
- lda #$01
- sta Joypad::JOYPAD1
- sta Joypad::m_buttons1, x ; Bit as a guard for the loop below.
- lsr a
- sta Joypad::JOYPAD1
-
- ;; Now the joypad is ready to accept reads.
-@joypad_unsafe_read_x_loop:
- lda Joypad::JOYPAD1, x
- and #%00000011 ; Ignore bits other than controller.
- cmp #$01 ; Set carry if and only if nonzero.
- rol Joypad::m_buttons1, x ; Carry -> bit 0; bit 7 -> Carry
- bcc @joypad_unsafe_read_x_loop
- rts
-
-;;;
-;; Safely read the first controller via a re-read algorithm.
-joypad_read:
- ldx #$00
-
- ;; NOTE: uncomment these two lines to also read safely the second
- ;; controller.
- ;;
- ;; jsr joypad_read_x
- ;; inx
-
- ;; NOTE: fallthrough
-
-;;;
-;; Safely read via a re-read algorithm the joypad as indexed by the X register
-;; (0 for controller 1; 1 for controller 2).
-joypad_read_x:
- jsr joypad_unsafe_read_x
-
- ;; The main idea around a re-read algorithm is that you read the controller
- ;; "unsafely" once, then you do it again and compare both reads. If they
- ;; were the same then we are on the safe side. Otherwise we would need to
- ;; loop until we get two identical reads. This sounds bad but in practice
- ;; it's not so much (and hey, if it worked for Super Mario Bros. 3, it
- ;; should work for us too :P). Otherwise there is the algorithm via OAM DMA,
- ;; but it sure is tricky.
-@joypad_read_x_reread:
- lda Joypad::m_buttons1, x
- pha
- jsr joypad_unsafe_read_x
- pla
- cmp Joypad::m_buttons1, x
- bne @joypad_read_x_reread
-
- rts