86Box/src/sound/snd_ps1.c

#include <stdarg.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <wchar.h>
#define HAVE_STDARG_H
#include <86box/86box.h>
#include <86box/io.h>
#include <86box/timer.h>
#include <86box/device.h>
#include <86box/sound.h>
#include <86box/snd_sn76489.h>


typedef struct {
    sn76489_t sn76489;
    uint8_t status, ctrl;
    uint64_t timer_latch;
    pc_timer_t timer_count;
    int timer_enable;
    uint8_t fifo[2048];
    int fifo_read_idx, fifo_write_idx;
    int fifo_threshold;
    uint8_t dac_val;
    int16_t buffer[SOUNDBUFLEN];
    int pos;
} ps1snd_t;


static void
ps1snd_update_irq_status(ps1snd_t *snd)
{
    if (((snd->status & snd->ctrl) & 0x12) && (snd->ctrl & 0x01))
        picint(1 << 7);
    else
        picintc(1 << 7);
}


static uint8_t
ps1snd_read(uint16_t port, void *priv)
{
    ps1snd_t *ps1snd = (ps1snd_t *)priv;
    uint8_t ret = 0xff;

    switch (port & 7) {
    case 0: /* ADC data */
        ps1snd->status &= ~0x10;
        ps1snd_update_irq_status(ps1snd);
        ret = 0;
        break;

    case 2: /* status */
        ret = ps1snd->status;
        ret |= (ps1snd->ctrl & 0x01);
        if ((ps1snd->fifo_write_idx - ps1snd->fifo_read_idx) >= 2048)
            ret |= 0x08; /* FIFO full */
        if (ps1snd->fifo_read_idx == ps1snd->fifo_write_idx)
            ret |= 0x04; /* FIFO empty */
        break;

    case 3: /* FIFO timer */
        /*
         * The PS/1 Technical Reference says this should return
         * thecurrent value, but the PS/1 BIOS and Stunt Island
         * expect it not to change.
         */
        ret = ps1snd->timer_latch;
        break;

    case 4:
    case 5:
    case 6:
    case 7:
        ret = 0;
    }

    return(ret);
}


static void
ps1snd_write(uint16_t port, uint8_t val, void *priv)
{
    ps1snd_t *ps1snd = (ps1snd_t *)priv;

    switch (port & 7) {
    case 0: /* DAC output */
        if ((ps1snd->fifo_write_idx - ps1snd->fifo_read_idx) < 2048) {
            ps1snd->fifo[ps1snd->fifo_write_idx & 2047] = val;
            ps1snd->fifo_write_idx++;
        }
        break;

    case 2: /* control */
        ps1snd->ctrl = val;
        if (! (val & 0x02))
            ps1snd->status &= ~0x02;
        ps1snd_update_irq_status(ps1snd);
        break;

    case 3: /* timer reload value */
        ps1snd->timer_latch = val;
        if (val)
            timer_set_delay_u64(&ps1snd->timer_count, ((0xff-val) * TIMER_USEC));
        else
            timer_disable(&ps1snd->timer_count);
        break;

    case 4: /* almost empty */
        ps1snd->fifo_threshold = val * 4;
        break;
    }
}


static void
ps1snd_update(ps1snd_t *ps1snd)
{
    for (; ps1snd->pos < sound_pos_global; ps1snd->pos++)        
        ps1snd->buffer[ps1snd->pos] = (int8_t)(ps1snd->dac_val ^ 0x80) * 0x20;
}


static void
ps1snd_callback(void *priv)
{
    ps1snd_t *ps1snd = (ps1snd_t *)priv;

    ps1snd_update(ps1snd);

    if (ps1snd->fifo_read_idx != ps1snd->fifo_write_idx) {
        ps1snd->dac_val = ps1snd->fifo[ps1snd->fifo_read_idx & 2047];
        ps1snd->fifo_read_idx++;
    }

    if ((ps1snd->fifo_write_idx - ps1snd->fifo_read_idx) == ps1snd->fifo_threshold)
        ps1snd->status |= 0x02; /*FIFO almost empty*/

    ps1snd->status |= 0x10; /*ADC data ready*/
    ps1snd_update_irq_status(ps1snd);

    timer_advance_u64(&ps1snd->timer_count, ps1snd->timer_latch * TIMER_USEC);
}


static void
ps1snd_get_buffer(int32_t *buffer, int len, void *priv)
{
    ps1snd_t *ps1snd = (ps1snd_t *)priv;
    int c;

    ps1_snd_update(ps1snd);

    for (c = 0; c < len * 2; c++)
        buffer[c] += ps1snd->buffer[c >> 1];

    ps1snd->pos = 0;
}


static void *
ps1snd_init(const device_t *info)
{
    ps1snd_t *ps1snd = malloc(sizeof(ps1snd_t));
    memset(ps1snd, 0x00, sizeof(ps1snd_t));

    sn76489_init(&ps1snd->sn76489, 0x0205, 0x0001, SN76496, 4000000);

    io_sethandler(0x0200, 1, ps1snd_read,NULL,NULL, ps1snd_write,NULL,NULL, ps1snd);
    io_sethandler(0x0202, 6, ps1snd_read,NULL,NULL, ps1snd_write,NULL,NULL, ps1snd);

    timer_add(&ps1snd->timer_count, ps1snd_callback, ps1snd, 0);

    sound_add_handler(ps1snd_get_buffer, ps1snd);

    return(ps1snd);
}


static void
ps1snd_close(void *priv)
{
    ps1snd_t *ps1snd = (ps1snd_t *)priv;

    free(ps1snd);
}


static const device_t ps1snd_device = {
    "IBM PS/1 Audio Card",
    0,
    0,
    ps1snd_init, ps1snd_close,
    NULL,
    { NULL },
    NULL
    NULL
};