4nes4snes/snes.c

/* Name: snes.c
 * Project: Multiple NES/SNES to USB converter
 * Author: Raphael Assenat <raph@raphnet.net>
 * Copyright: (C) 2007 Raphael Assenat <raph@raphnet.net>
 * License: Proprietary, free under certain conditions. See Documentation.
 * Tabsize: 4
 */
#define F_CPU   12000000L  

#include <avr/io.h>
#include <avr/interrupt.h>
#include <util/delay.h>
#include <avr/pgmspace.h>
#include <string.h>
#include "gamepad.h"
#include "leds.h"
#include "snes.h"

#define REPORT_SIZE		12
#define GAMEPAD_BYTES	8	/* 2 byte per snes controller * 4 controllers */

/******** IO port definitions **************/
#define SNES_LATCH_DDR	DDRC
#define SNES_LATCH_PORT	PORTC
#define SNES_LATCH_BIT	(1<<4)

#define SNES_CLOCK_DDR	DDRC
#define SNES_CLOCK_PORT	PORTC
#define SNES_CLOCK_BIT	(1<<5)

#define SNES_DATA_PORT	PORTC
#define SNES_DATA_DDR	DDRC
#define SNES_DATA_PIN	PINC
#define SNES_DATA_BIT1	(1<<3)	/* controller 1 */
#define SNES_DATA_BIT2	(1<<2)	/* controller 2 */
#define SNES_DATA_BIT3	(1<<1)	/* controller 3 */
#define SNES_DATA_BIT4	(1<<0)	/* controller 4 */

/********* IO port manipulation macros **********/
#define SNES_LATCH_LOW()	do { SNES_LATCH_PORT &= ~(SNES_LATCH_BIT); } while(0)
#define SNES_LATCH_HIGH()	do { SNES_LATCH_PORT |= SNES_LATCH_BIT; } while(0)
#define SNES_CLOCK_LOW()	do { SNES_CLOCK_PORT &= ~(SNES_CLOCK_BIT); } while(0)
#define SNES_CLOCK_HIGH()	do { SNES_CLOCK_PORT |= SNES_CLOCK_BIT; } while(0)

#define SNES_GET_DATA1()	(SNES_DATA_PIN & SNES_DATA_BIT1)
#define SNES_GET_DATA2()	(SNES_DATA_PIN & SNES_DATA_BIT2)
#define SNES_GET_DATA3()	(SNES_DATA_PIN & SNES_DATA_BIT3)
#define SNES_GET_DATA4()	(SNES_DATA_PIN & SNES_DATA_BIT4)

/*********** prototypes *************/
static void snesInit(void);
static void snesUpdate(void);
static char snesChanged(void);
static void snesBuildReport(unsigned char *reportBuffer);


// the most recent bytes we fetched from the controller
static unsigned char last_read_controller_bytes[GAMEPAD_BYTES];

// the most recently reported bytes
static unsigned char last_reported_controller_bytes[GAMEPAD_BYTES];

// indicates if a controller is in NES mode
static unsigned char nesMode=0;	/* Bit0: controller 1, Bit1: controller 2...*/

static void snesInit(void)
{
	unsigned char sreg;
	sreg = SREG;
	cli();
	
	// clock and latch as output
	SNES_LATCH_DDR |= SNES_LATCH_BIT;
	SNES_CLOCK_DDR |= SNES_CLOCK_BIT;
	
	// data as input
	SNES_DATA_DDR &= ~(SNES_DATA_BIT1 | SNES_DATA_BIT2 | SNES_DATA_BIT3 | SNES_DATA_BIT4 );
	// enable pullup. This should prevent random toggling of pins
	// when no controller is connected.
	SNES_DATA_PORT |= (SNES_DATA_BIT1 | SNES_DATA_BIT2 | SNES_DATA_BIT3 | SNES_DATA_BIT4 );

	// clock is normally high
	SNES_CLOCK_PORT |= SNES_CLOCK_BIT;

	// LATCH is Active HIGH
	SNES_LATCH_PORT &= ~(SNES_LATCH_BIT);

	nesMode = 0;
	snesUpdate();
	
	/* Snes controller buttons are sent in this order:
	 * 1st byte: B Y SEL START UP DOWN LEFT RIGHT 
	 * 2nd byte: A X L R 1 1 1 1
	 *
	 * Nes controller buttons are sent in this order:
	 * One byte: A B SEL START UP DOWN LEFT RIGHT
	 *
	 * When an additional byte is read from a NES controller,
	 * all bits are 0. Because the data signal is active low,
	 * this corresponds to pressed buttons. When we read
	 * from the controller for the first time, detect NES
	 * controllers by checking those 4 bits.
	 **/
	if (last_read_controller_bytes[1]==0xFF)
		nesMode |= 1;

	if (last_read_controller_bytes[3]==0xFF)
		nesMode |= 2;

	if (last_read_controller_bytes[5]==0xFF)
		nesMode |= 4;

	if (last_read_controller_bytes[7]==0xFF)
		nesMode |= 8;

	SREG = sreg;
}


/*
 *
       Clock Cycle     Button Reported
        ===========     ===============
        1               B
        2               Y
        3               Select
        4               Start
        5               Up on joypad
        6               Down on joypad
        7               Left on joypad
        8               Right on joypad
        9               A
        10              X
        11              L
        12              R
        13              none (always high)
        14              none (always high)
        15              none (always high)
        16              none (always high)
 *
 */

static void snesUpdate(void)
{
	int i;
	unsigned char tmp1=0;
	unsigned char tmp2=0;
	unsigned char tmp3=0;
	unsigned char tmp4=0;

	SNES_LATCH_HIGH();
	_delay_us(12);
	SNES_LATCH_LOW();

	for (i=0; i<8; i++)
	{
		_delay_us(6);
		SNES_CLOCK_LOW();
		
		tmp1 <<= 1;	
		tmp2 <<= 1;	
		tmp3 <<= 1;	
		tmp4 <<= 1;
		if (!SNES_GET_DATA1()) { tmp1 |= 1; }
		if (!SNES_GET_DATA2()) { tmp2 |= 1; }
		if (!SNES_GET_DATA3()) { tmp3 |= 1; }
		if (!SNES_GET_DATA4()) { tmp4 |= 1; }

		_delay_us(6);
		
		SNES_CLOCK_HIGH();
	}
	last_read_controller_bytes[0] = tmp1;
	last_read_controller_bytes[2] = tmp2;
	last_read_controller_bytes[4] = tmp3;
	last_read_controller_bytes[6] = tmp4;

	for (i=0; i<8; i++)
	{
		_delay_us(6);

		SNES_CLOCK_LOW();

		// notice that this is different from above. We
		// want the bits to be in reverse-order
		tmp1 >>= 1;	
		tmp2 >>= 1;	
		tmp3 >>= 1;	
		tmp4 >>= 1;	
		if (!SNES_GET_DATA1()) { tmp1 |= 0x80; }
		if (!SNES_GET_DATA2()) { tmp2 |= 0x80; }
		if (!SNES_GET_DATA3()) { tmp3 |= 0x80; }
		if (!SNES_GET_DATA4()) { tmp4 |= 0x80; }
		
		_delay_us(6);
		SNES_CLOCK_HIGH();
	}
	/* Force extra bits to 0 when in NES mode. Otherwise, if
	 * we read zeros on the wire, we will have permanantly 
	 * pressed buttons */
	last_read_controller_bytes[1] = (nesMode & 1) ? 0x00 : tmp1;
	last_read_controller_bytes[3] = (nesMode & 2) ? 0x00 : tmp2;
	last_read_controller_bytes[5] = (nesMode & 4) ? 0x00 : tmp3;
	last_read_controller_bytes[7] = (nesMode & 8) ? 0x00 : tmp4;

}

static char snesChanged(void)
{
	static int first = 1;
	if (first) { first = 0;  return 1; }
	
	return memcmp(last_read_controller_bytes, 
					last_reported_controller_bytes, GAMEPAD_BYTES);
}

static char getX(unsigned char nesByte1)
{
	char x = 128;
	if (nesByte1&0x1) { x = 255; }
	if (nesByte1&0x2) { x = 0; }
	return x;
}

static char getY(unsigned char nesByte1)
{
	char y = 128;
	if (nesByte1&0x4) { y = 255; }
	if (nesByte1&0x8) { y = 0; }
	return y;
}

static unsigned char snesReorderButtons(unsigned char bytes[2])
{
	unsigned char v;

	/* pack the snes button bits, which are on two bytes, in
	 * one single byte. */
	v =	(bytes[0]&0x80)>>7;
	v |= (bytes[0]&0x40)>>5;
	v |= (bytes[0]&0x20)>>3;
	v |= (bytes[0]&0x10)>>1;
	v |= (bytes[1]&0x0f)<<4;

	return v;
}

static void snesBuildReport(unsigned char *reportBuffer)
{
	/* last_read_controller_bytes[] structure:
	 *
	 * [0] : controller 1, 8 first bits (dpad + start + sel + y|a + b)
	 * [1] : controller 1, 8 snes extra bits (4 lower bits are buttons)
	 *
	 * [2] : controller 2, 8 first bits
	 * [3] : controller 2, 4 extra snes buttons
	 *
	 * [4] : controller 3, 8 first bits
	 * [5] : controller 3, 4 extra snes buttons
	 *
	 * [6] : controller 4, 8 first bits
	 * [7] : controller 4, 4 extra snes buttons
	 */

	if (reportBuffer != NULL)
	{
		reportBuffer[0]=getX(last_read_controller_bytes[0]);
		reportBuffer[1]=getY(last_read_controller_bytes[0]);
		reportBuffer[2]=getX(last_read_controller_bytes[2]);
		reportBuffer[3]=getY(last_read_controller_bytes[2]);
		reportBuffer[4]=getX(last_read_controller_bytes[4]);
		reportBuffer[5]=getY(last_read_controller_bytes[4]);
		reportBuffer[6]=getX(last_read_controller_bytes[6]);
		reportBuffer[7]=getY(last_read_controller_bytes[6]);

		if (nesMode & 0x01)
			reportBuffer[8] = last_read_controller_bytes[0] & 0xf0;
		else
			reportBuffer[8] = snesReorderButtons(&last_read_controller_bytes[0]);

		if (nesMode & 0x02)
			reportBuffer[9] = last_read_controller_bytes[2] & 0xf0;
		else
			reportBuffer[9] = snesReorderButtons(&last_read_controller_bytes[2]);

		if (nesMode & 0x04)
			reportBuffer[10] = last_read_controller_bytes[4] & 0xf0;
		else
			reportBuffer[10] = snesReorderButtons(&last_read_controller_bytes[4]);

		if (nesMode & 0x08)
			reportBuffer[11] = last_read_controller_bytes[6] & 0xf0;
		else
			reportBuffer[11] = snesReorderButtons(&last_read_controller_bytes[6]);


	}
	memcpy(last_reported_controller_bytes, 
			last_read_controller_bytes, 
			GAMEPAD_BYTES);	
}

const char snes_usbHidReportDescriptor[] PROGMEM = {
    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)
    0x09, 0x04,                    // USAGE (Joystick)
    0xa1, 0x01,                    // COLLECTION (Application)
    0x09, 0x01,                    //   USAGE (Pointer)
    0xa1, 0x00,                    //   COLLECTION (Physical)
    
	0x09, 0x30,                    //     USAGE (X)
    0x09, 0x31,                    //     USAGE (Y)
	0x09, 0x32,					   //     USAGE (Z)
	0x09, 0x33,					   //	  USAGE (Rx) 
	0x09, 0x34,					   //	  USAGE (Ry)
	0x09, 0x35,					   //	  USAGE (Rz)
	0x09, 0x36,					   //     USAGE (Slider)
	0x09, 0x37,					   //	  USAGE (Dial)

    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x26, 0xff, 0x00,              //     LOGICAL_MAXIMUM (255)
    0x75, 0x08,                    //   REPORT_SIZE (8)
    0x95, 0x08,                    //   REPORT_COUNT (8)
    0x81, 0x02,                    //   INPUT (Data,Var,Abs)
    0xc0,                          // END_COLLECTION

    0x05, 0x09,                    // USAGE_PAGE (Button)
    0x19, 1,                       //   USAGE_MINIMUM (Button 1)
    0x29, 32,                       //   USAGE_MAXIMUM (Button 32)
    0x15, 0x00,                    //   LOGICAL_MINIMUM (0)
    0x25, 0x01,                    //   LOGICAL_MAXIMUM (1)
    0x75, 1,                       // REPORT_SIZE (1)
    0x95, 32,                       // REPORT_COUNT (32)
    0x81, 0x02,                    // INPUT (Data,Var,Abs)

    0xc0                           // END_COLLECTION
};

Gamepad SnesGamepad = {
	report_size: 		REPORT_SIZE,
	reportDescriptorSize:	sizeof(snes_usbHidReportDescriptor),
	init: 			snesInit,
	update: 		snesUpdate,
	changed:		snesChanged,
	buildReport:		snesBuildReport
};

Gamepad *snesGetGamepad(void)
{
	SnesGamepad.reportDescriptor = (void*)snes_usbHidReportDescriptor;

	return &SnesGamepad;
}