OPLL device interface

Inspect, discover, enable/disable to access registers, of the OPLL sound chip. More...

Collaboration diagram for OPLL device interface:

Data Structures
struct	OPLL_Device
	Device interface for OPLL sound chip. More...
struct	OPLL
	OPLL Handle. More...

Functions
uint8_t	OPLL_inspect (uint8_t slot)
	MSX Inspect whether OPLL is on the given slot.
uint8_t	OPLL_find (struct OPLL *opll)
	MSX Find OPLL sound chip.
void	OPLL_enable (const struct OPLL *opll)
	MSX Enable OPLL sound chip.
void	OPLL_disable (const struct OPLL *opll)
	MSX Disable OPLL sound chip.

Detailed Description

Inspect, discover, enable/disable to access registers, of the OPLL sound chip.

Example
The following code detects the MSX-MUSIC (OPLL) and plays a test tone if detected.

// -*- coding: utf-8-unix -*-
/*
 * Copyright (c) 2021-2024 Daishi Mori (mori0091)
 *
 * This software is released under the MIT License.\n
 * See https://github.com/mori0091/libmsx/blob/main/LICENSE
 *
 * GitHub libmsx project\n
 * https://github.com/mori0091/libmsx
 */
#include <string.h>
 
#include <msx.h>
#include <opll.h>
 
static struct OPLL opll;
 
#define LO_BYTE(x) (uint8_t)((x) & 0xff)
#define HI_BYTE(x) (uint8_t)(((x) >> 8) & 0xff)
 
#define SUS_OFF  (0)
#define KEY_OFF  (0)
#define SUS_ON   (uint16_t)(1 << 13)
#define KEY_ON   (uint16_t)(1 << 12)
#define BLOCK(x) (uint16_t)((x) << 9)
#define F_NUM(x) (uint16_t)(x)
 
#define INST(x)  (uint8_t)((x) << 4)
#define VOL(x)   (uint8_t)((x) & 0x0f)
 
void test_OPLL(void) {
  // If OPLL was not found, nothing is done.
  if (!opll.slot) return;
  {
    // 9 channels mode
    opll.device->write(0x0e, 0x00);
 
    // ch1 : Forces to KEY-OFF before next KEY-ON.
    opll.device->write(0x10, 0);
    opll.device->write(0x20, 0);
 
    // ch1 : INST=3, VOL=0
    // \note
    // VOL(0) means maximum volume, VOL(15) means minimum volume.
    // VOL(a) means "-3a dB of the maximum volume" (i.e. Vmax * 10^(-0.3a))
    opll.device->write(0x30, (INST(3) | VOL(0)));
 
    // ch1 : O4 G
    uint16_t x = (SUS_OFF | KEY_ON | BLOCK(4) | F_NUM(257));
    opll.device->write(0x10, LO_BYTE(x));
    opll.device->write(0x20, HI_BYTE(x));
 
    // \note
    // Interrupts are disabled by calling `opll.device->write()`, so interrupts
    // must be enabled at the end.
    __asm__("ei");
    sleep_millis(2000);
  }
}
 
void main(void) {
  OPLL_find(&opll);             // Find OPLL
  OPLL_enable(&opll);           // Enable OPLL, if found.
  for (;;) {
    test_OPLL();
  }
}

---

Data Structure Documentation

OPLL

struct OPLL

OPLL Handle.

See also

OPLL_find()

OPLL_enable()

OPLL_disable()

Definition at line 74 of file opll.h.

Collaboration diagram for OPLL:

Data Fields
uint8_t	slot	Slot address of the OPLL.
uint8_t	version	Version/Identifier of the OPLL. 1 if FMPAC, 2 or greater value if other OPLL, bit #7 is set if it is the internal OPLL.
const struct OPLL_Device *	device	Pointer to device interface.

Function Documentation

OPLL_inspect()

uint8_t OPLL_inspect

(

uint8_t

slot

)

MSX Inspect whether OPLL is on the given slot.

Parameters

slot	a slot address

Returns

Version/Identifier of the OPLL.

• 0 if not OPLL,
• 1 if FMPAC,
• 2 or greater value if other OPLL,
• bit #7 is set if it is the internal OPLL.

OPLL_find()

uint8_t OPLL_find

(

struct OPLL *

opll

)

MSX Find OPLL sound chip.

Parameters

opll	[out] pointer to a OPLL handle to be initialized.

Returns

the slot address of OPLL if found, 0 otherwise.

Postcondition

If no OPLL found, 0 is set to opll->slot.

If a OPLL found;

• the slot address of OPLL is set to opll->slot,
• 1 is set to opll->version if FMPAC,
• 2 or greater value is set to opll->version if other OPLL,
• bit #7 is set if it is the internal OPLL.
• the device interface is set to opll->device.

OPLL_enable()

void OPLL_enable

(

const struct OPLL *

opll

)

MSX Enable OPLL sound chip.

Expose OPLL sound chip on the slot opll->slot and enable to access registers of the sound chip.

The opll shall point to a OPLL handle initialized by OPLL_find().

Parameters

opll	pointer to the OPLL handle.

OPLL_disable()

void OPLL_disable

(

const struct OPLL *

opll

)

MSX Disable OPLL sound chip.

Unexpose OPLL sound chip on the slot opll->slot and disable to access registers of the sound chip.

The opll shall point to a OPLL handle initialized by OPLL_find().

Parameters

opll	pointer to the OPLL handle.