failed attempt at volume pwm (commented out)

diff --git a/bootcard.asm b/bootcard.asm
index e582ebd..71e1619 100644 (file)
--- a/bootcard.asm
+++ b/bootcard.asm
@@ -9,14 +9,13 @@
 data_start     equ 7e00h
 nticks         equ data_start
 muscur         equ nticks + 4
+spkstat                equ muscur + 4
+vol            equ spkstat + 4
 
 osc_freq       equ 1193182
 PIT_DATA0      equ 40h
-PIT_DATA2      equ 42h
 PIT_CMD                equ 43h
 PIT_CMD_CHAN0  equ 00h
-PIT_CMD_CHAN1  equ 40h
-PIT_CMD_CHAN2  equ 80h
 PIT_CMD_HILO   equ 30h
 PIT_CMD_SQWAVE equ 06h
 KB_CTRL                equ 61h
@@ -49,17 +48,19 @@ KB_CTRL             equ 61h
        out PIT_DATA0 + %1, al
 %endmacro
 
-       xor ax, ax
+       xor eax, eax
        mov ds, ax
        mov ss, ax
        mov sp, 7c00h
 
-       mov dword [nticks], 0
-       mov dword [muscur], 0
+       mov [nticks], eax
+       mov [muscur], eax
+       ;mov [spkstat], eax
+       ;mov word [vol], 04h
        mov word [32], timer_intr
        mov word [34], 0
 
-       settimer 0, DIV_ROUND(osc_freq, 250)
+       settimer 0, DIV_ROUND(osc_freq, 100)
 
        mov ax, 13h
        int 10h
@@ -102,23 +103,40 @@ timer_intr:
 
        mov bx, [muscur]
        shl bx, 2
-       mov cx, [music + bx]
+       mov cx, [music + bx]    ; event time
        cmp cx, 0ffffh
        jz .off
        cmp ax, cx
-       jb .eoi
+       jb .dopwm
 
        inc dword [muscur]
-       mov ax, [music + 2 + bx] ; grab timeout
+       mov ax, [music + 2 + bx] ; event counter reload
        test ax, ax
        jz .off
        mov bx, ax
-
        settimer 2, bx
        spkon
-       jmp .eoi
+       mov word [spkstat], 1
+       jmp .dopwm
 
 .off:  spkoff
+       mov word [spkstat], 0
+       jmp .eoi
+
+       ; PWM for volume control
+.dopwm:        jmp .eoi
+       spkoff
+       mov ax, [spkstat]
+       test ax, ax
+       jz .eoi
+       mov ax, [nticks]
+       and ax, 0fh
+       cmp ax, [vol]
+       jae .pwmoff
+       spkon
+       jmp .eoi
+.pwmoff:
+       spkoff
 
 .eoi:  mov al, 20h
        out 20h, al     ; EOI
@@ -128,14 +146,28 @@ str1:     db 'message message blah',0
 str2:  db 'Michael & Athina',0
 
 music:
-       dw 0, 500
-       dw 10, 0
-       dw 20, 2000
-       dw 30, 0
-       dw 40, 500
-       dw 50, 0
-       dw 60, 2000
-       dw 70, 0
+       dw 0, 2000
+       dw 10, 1900
+       dw 20, 1800
+       dw 30, 1700
+       dw 40, 1600
+       dw 50, 1500
+       dw 60, 1400
+       dw 70, 1300
+       dw 80, 1200
+       dw 90, 1100
+       dw 100, 1000
+       dw 110, 1100
+       dw 120, 1200
+       dw 130, 1300
+       dw 140, 1400
+       dw 150, 1500
+       dw 160, 1600
+       dw 170, 1700
+       dw 180, 1800
+       dw 190, 1900
+       dw 200, 2000
+       dw 210, 0
        dw 0ffffh, 0
 
        times 446-($-$$) db 0