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keen: working on sound

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This commit is contained in:
Vince Weaver 2024-04-01 16:19:40 -04:00
parent 4df133005d
commit 1be1d94080
2 changed files with 65 additions and 28 deletions
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4
games/keen/SFX
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@ -6,8 +6,8 @@ Based on dumped code by the "KeenFX" tool
Note: 65535-value = note freq
3) WLDENTERSND
64155, 10
63495, 5
64155, 10 ; 1380Hz F6?
63495, 5 ;
0,16
62355,2
62175,16

89
games/keen/speaker_tone.s
View File

@ -1,21 +1,40 @@
; based on code from here
; this code was widely shared for playing tones on Apple II
; by POKEing the machine language and CALLing from BASIC
; it's originally by Paul Lutus, from the Apple II Red Book p45
; it's hard to find good info on this, but loading from $C030
; "toggles" the speaker. So toggling twice is esentially a square wave?
; using regular load/store/bit of $C030 is safe. Some of the more
; advanced addressing modes can double-toggle due to how some 6502
; implementations run the address bus
; these seem to have been calculated assuming a 1MHz clock
; but the Apple II actually runs at roughly 1.023MHz
; or a frequency of 1/(speaker_freq*20.46e-6)
; to go other way, speaker_freq=1/(freq*20.46e-6)
; this table of notes was from
; http://eightbitsoundandfury.ld8.org/programming.html
; but seems off a bit and also assumes 1MHz clock
; A,X,Y trashed
; duration also trashed
NOTE_C3 = 255
NOTE_CSHARP3 = 241
NOTE_D3 = 227
NOTE_DSHARP3 = 214
NOTE_E3 = 202
NOTE_F3 = 191
NOTE_FSHARP3 = 180
NOTE_G3 = 170
NOTE_GSHARP3 = 161
NOTE_A3 = 152
NOTE_ASHARP3 = 143
NOTE_B3 = 135
; 1MHz 1.023MHz
NOTE_C3 = 255 ; G3=5217us = 192Hz (G3, 5218us = 196Hz 249)
NOTE_CSHARP3 = 241 ; 4931us = 203Hz (G#3, 4931us = 207Hz
NOTE_D3 = 227 ;
NOTE_DSHARP3 = 214
NOTE_E3 = 202
NOTE_F3 = 191
NOTE_FSHARP3 = 180
NOTE_G3 = 170
NOTE_GSHARP3 = 161
NOTE_A3 = 152
NOTE_ASHARP3 = 143
NOTE_B3 = 135 ; 1350us = 740Hz (F#5)
NOTE_C4 = 128
NOTE_CSHARP4 = 121
@ -43,20 +62,38 @@ NOTE_A5 = 38
NOTE_ASHARP5 = 36
NOTE_B5 = 34
; B5 = 988 Hz, 1021us
;=====================================================
; speaker tone
;=====================================================
; A,X,Y trashed
; duration also trashed
; this was designed by basic to be poked into 770 ($302)
; on an Applesoft CALL, X=$9d, Y=$02 (A,Y = Address to call)
; it was originally designed for Integer BASIC where Y=0 on call
; the inner freq loop is roughly FREQ*10cycles
; so the square wave generated has a period of
; freq*20*1.023us
; or a frequency of 1/(freq*20.46e-6)
speaker_tone:
lda $C030 ; click speaker
ldy #0 ; 3
speaker_tone_loop:
lda $C030 ; click speaker ; 4
speaker_loop:
dey ; y never set?
bne slabel1 ; duration roughly 256*?
dec speaker_duration ; (Duration)
beq done_tone
slabel1:
dex
bne speaker_loop
ldx speaker_frequency ; (Frequency)
jmp speaker_tone
dey ; ; 2
bne freq_loop ; ; 2/3
dec speaker_duration ; (Duration) ; 6
beq done_tone ; 2/3
freq_loop:
dex ; 2
bne speaker_loop ; 2/3
ldx speaker_frequency ; (Frequency) ; 4
jmp speaker_tone_loop ; 3
done_tone:
rts