You want to do a game/program for the 68K calculators, and
want sound in it? We here at JEsystems have a quite nice, and easy sound
function that should work just fine for you. And the code is really simple,
check this out:
Thanks to Francois Leiber for the basis of this code! For an example, download JesJump
v1.0 and see how the code is utilized.
Note: This code has been updated since the
release of JesJump, to add support for VTI sound and rests. It is based off
of the Midi68k source code, which can be downloaded through our Download
page.
// This contains the HW2 status.
// 0 for HW1s, 1 for HW2s. This is used because they are
// different for sound.
short hardwarever;
// This works through Auto-Int-5, as an always-going-counter.
volatile short count;
DEFINE_INT_HANDLER(count_int)
{
++count;
}
//=======================================================
// VTI detection routine (thanx, Julien Muchembled)
//
// this routine utilizes a bug in VTI: you can set even non-existing flags in
// the status register and query them later!
//========================================================
extern short IsVTI(void);
asm("IsVTI: trap #12; /* enter supervisor mode. returns old (%sr) in %d0.w */
move.w #0x3000,%sr; /* set a non-existing flag in %sr (but keep s-flag !!) */
swap %d0; /* save %d0.w content in upper part of %d0 */ move.w %sr,%d0; /* get %sr
content and check for non-existing flag */ btst #12,%d0; /* this non-existing
flag can only be set on the VTI */ bne __VTI; swap %d0; /* restore old %sr
content and return 0 */ move.w %d0,%sr; moveq #0,%d0; rts;__VTI: swap %d0; /*
restore old %sr content and return 1 */ move.w %d0,%sr; moveq #1,%d0; rts;");
short VTI;
//Duration is in seconds*350.
void rest(long duree)
{
short start = count;
while (count - start < duree);
}
//Thanks to Francois Leiber for the beep() code.
//However, it has been slightly modified with ASM
//so it works with VTI's sound feature.
//Duration is in a special form: (5400/tempo)*duration
//(5400 is 27x200, i.e. a quarter note is 27 long at tempo 200)
//Tempo is in Beats Per Minute.
//Duration is the note length in relation to a quarter note.
//For example, an eighth note is 0.5, a quarter note 1, a whole note 4, etc.
void beep(short freq, long duree)
{
long int loop, maxloop ;
short int delay;
short int i, j;
if(VTI) duree=(duree*15)>>4;
maxloop = freq*duree/50;
j = peekIO(0x60000E);
freq = (hardwarever ? 364000 : 278000)/freq ;
asm("bset.b #6,0x60000C");
for (loop = 0 ; loop < maxloop ; loop++)
{
asm("bchg.b #0,0x60000E;bchg.b #1,0x60000E;");
for (i = 0 ; i <= freq ; i--) i += 2 ;
}
asm("bclr.b #0,0x60000E;bclr.b #1,0x60000E;move.b #0x8D,0x60000C;");
for(delay=0;delay<(100*duree);delay+=2) delay--;
}
//An example of a main function that uses the beep code (from Midi68k)
void _main(void)
{
INT_HANDLER save_int_4 = GetIntVec(AUTO_INT_4);
INT_HANDLER save_int_1 = GetIntVec(AUTO_INT_1);
INT_HANDLER save_int_5 = GetIntVec(AUTO_INT_5);
short int total = sizeof(music)/sizeof(music[0]); //Determines the # elements in
the music array
short int current=0;
/* Checks the calculator hardware version */
short *hwptr;
hwptr = (short *)FL_getHardwareParmBlock();
hardwarever = ((*hwptr)==20)?0:1;
/*-----------------------------------------*/
VTI=IsVTI();
//Directs ints to nothing
SetIntVec(AUTO_INT_4, DUMMY_HANDLER);
SetIntVec(AUTO_INT_5, DUMMY_HANDLER);
//Auto Int 1 is called 350 times per second.
SetIntVec(AUTO_INT_1, count_int);
//Get the link port ready
OSLinkReset();
OSLinkOpen();
clrscr();
//Display some information
printf("\n\nBeethoven-Moonlight Sonata");
printf("\n\n\nCreated by Midi68k\nBy Malcolm Smith\nhttp://jesystems.cjb.net\n\nHOLD
Esc to Quit.");
while( !(_keytest (RR_ESC)) && current<total)
{
//If the frequency is 0, it is a rest.
if(!music[current][1]) rest(music[current][0]);
//Otherwise, play the note
else if(music[current][0]>0) beep(music[current][1],music[current][0]);
current++;
}
SetIntVec(AUTO_INT_4, save_int_4);
SetIntVec(AUTO_INT_1, save_int_1);
SetIntVec(AUTO_INT_5, save_int_5);
OSLinkReset();
GKeyFlush();
OSTimerRestart(APD_TIMER);
}
|
If you have read the source code for the former
sound driver, don't let all the new stuff overwhelm you :-)
The ASM instructions all deal with the link port, such as
opening it for communication, and sending sound data.
The VTI detection code and line "if(VTI) duree=(duree*15)>>4;"
are important. I have discovered that notes are longer on VTI than on a real
calculator. That line of code corrects for this.
The above source code is very well commented, and it
can basically be used "as-is". However, I left out the music array. This array
can be generated from a Type-0 single-channel MIDI file using Midi68k.
If you're feeling brave, it can also be done manually.
See this page for a
list of MIDI frequencies, and durations are fairly easy to figure out (see the
comments above the rest() and beep() code for more information).
Another thing is
that you need to disable all interrupts for a stable sound (or at least
direct Auto-Ints 1,4, and 5 to a DUMMY_HANDLER).
If you don't know how to make the hardware for your
headphones, check out our TI-sound information page.
You can now also use the "Enable Sound" feature in VTI.
Enjoy your sound!
--Malcolm Smith, 7/7/2002 |
