/* MPU.C
 * This file contains low-level routines for MIDI I/O through the
 * Roland MPU-401.
 *
 * DOS idiosyncracies:
 *	int inportb(port)
 *		int port;
 * Read a byte from port 'port' and return it.
 *	outportb(port,value)
 *		int port;
 *		char value;
 * Send the byte 'value' to port 'port'.
 *
 * Copyright (C) 1991 by Andrew Arensburger. Permission is granted to
 * use, copy and/or distribute this file freely for non-commercial purposes,
 * as long as this notice remains intact. Any commercial use is prohibited
 * without express permission from the author.
 *
 * If you make any changes, fix bugs, etc., please send them to me that I
 * might coordinate fixes and improvements.
 */

#ifdef DEBUG
#include <stdio.h>		/* For debugging only */
int mpu_debug = 0;
#endif
#include <dos.h>
#include "mpu.h"

/* MPU_UART
 * Put the MPU into UART mode (best for SysEx I/O).
 */
mpu_uart()
{
#ifdef DEBUG
	if (mpu_debug)
		fprintf(stderr, "(UART) ");
#endif
	outportb(MPU_CMD, (unsigned char) CMD_UART);
}

/* MPU_RESET
 * Reset the MPU.
 */
mpu_reset()
{
#ifdef DEBUG
	if (mpu_debug)
		fprintf(stderr, "(reset) ");
#endif
	outportb(MPU_CMD, (unsigned char) CMD_RESET);
}

/* FLUSH_NONSYSX
 * Read in any "normal" (i.e., non-SysEx) messages from the EPS. This is
 * necessary in cases where not reading them could clog up the MPU.
 * Returns the first SysEx command byte received.
 */
unsigned char flush_nonsysx()
{
	unsigned char status;

	for (;;)
	{
		if (!DSR || ((status = (unsigned char) mpu_rbyte()) >= 0xf0))
			return(status);
	}
}

/* MPU_SBYTE
 * Send a byte to the MPU.
 */
mpu_sbyte(b)
unsigned char b;		/* The byte to be sent */
{
	flush_nonsysx();	/* Flush any pending input */
	while (!DRR)		/* Wait until MPU is ready */
	;
#ifdef DEBUG
	if (mpu_debug)
		fprintf(stderr, "(0x%2x) ", b);
#endif
	outportb(MPU_DATA,b);	/* Send the byte */
}

/* MPU_RBYTE
 * Receive a byte from the MPU. Returns the byte read, or -1 in case
 * of error.
 */
int mpu_rbyte()
{
	int retval;		/* Return value */

	while (!DSR)		/* Wait until MPU is ready to send */
	;
	retval = inportb(MPU_DATA);
#ifdef DEBUG
	if (mpu_debug)
		fprintf(stderr, "[0x%2x] ", retval);
#endif
	return(retval);
}

/* MPU_INIT
 * Initialize the MPU-401 from power-up state to a sane state: put it in
 * UART mode, and flush its buffers to make sure it is ready to send and
 * receive UART data.
 */
mpu_init()
{
	inportb(MPU_STAT);
	inportb(MPU_DATA);
	while (DSR)
		inportb(MPU_DATA),wait(1);
	mpu_uart();
	wait(2);
	while (DSR)
		inportb(MPU_DATA),wait(1);
}