Pico-GB/src/main.c

/**
 * Copyright (C) 2022 by Mahyar Koshkouei <mk@deltabeard.com>
 * 
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

// Peanut-GB emulator settings
#define ENABLE_LCD	1
#define ENABLE_SOUND	1
#define ENABLE_SDCARD	1
#define PEANUT_GB_HIGH_LCD_ACCURACY 1
#define PEANUT_GB_USE_BIOS 0

/* Use DMA for all drawing to LCD. Benefits aren't fully realised at the moment
 * due to busy loops waiting for DMA completion. */
#define USE_DMA		0

/**
 * Reducing VSYNC calculation to lower multiple.
 * When setting a clock IRQ to DMG_CLOCK_FREQ_REDUCED, count to
 * SCREEN_REFRESH_CYCLES_REDUCED to obtain the time required each VSYNC.
 * DMG_CLOCK_FREQ_REDUCED = 2^18, and SCREEN_REFRESH_CYCLES_REDUCED = 4389.
 * Currently unused.
 */
#define VSYNC_REDUCTION_FACTOR 16u
#define SCREEN_REFRESH_CYCLES_REDUCED (SCREEN_REFRESH_CYCLES/VSYNC_REDUCTION_FACTOR)
#define DMG_CLOCK_FREQ_REDUCED (DMG_CLOCK_FREQ/VSYNC_REDUCTION_FACTOR)

/* C Headers */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

/* RP2040 Headers */
#include <hardware/pio.h>
#include <hardware/clocks.h>
#include <hardware/dma.h>
#include <hardware/spi.h>
#include <hardware/sync.h>
#include <hardware/flash.h>
#include <hardware/timer.h>
#include <hardware/vreg.h>
#include <pico/bootrom.h>
#include <pico/stdio.h>
#include <pico/stdlib.h>
#include <pico/multicore.h>
#include <sys/unistd.h>
#include <hardware/irq.h>

/* Project headers */
#include "hedley.h"
#include "minigb_apu.h"
#include "peanut_gb.h"
#include "mk_ili9225.h"
#include "sdcard.h"
#include "i2s.h"
#include "gbcolors.h"

/* GPIO Connections. */
#define GPIO_UP		2
#define GPIO_DOWN	3
#define GPIO_LEFT	4
#define GPIO_RIGHT	5
#define GPIO_A		6
#define GPIO_B		7
#define GPIO_SELECT	8
#define GPIO_START	9
#define GPIO_CS		17
#define GPIO_CLK	18
#define GPIO_SDA	19
#define GPIO_RS		20
#define GPIO_RST	21
#define GPIO_LED	22

#if ENABLE_SOUND
/**
 * Global variables for audio task
 * stream contains N=AUDIO_SAMPLES samples
 * each sample is 32 bits
 * 16 bits for the left channel + 16 bits for the right channel in stereo interleaved format)
 * This is intended to be played at AUDIO_SAMPLE_RATE Hz
 */
uint16_t *stream;
#endif

/** Definition of ROM data
 * We're going to erase and reprogram a region 1Mb from the start of the flash
 * Once done, we can access this at XIP_BASE + 1Mb.
 * Game Boy DMG ROM size ranges from 32768 bytes (e.g. Tetris) to 1,048,576 bytes (e.g. Pokemod Red)
 */
#define FLASH_TARGET_OFFSET (1024 * 1024)
const uint8_t *rom = (const uint8_t *) (XIP_BASE + FLASH_TARGET_OFFSET);
static unsigned char rom_bank0[65536];

static uint8_t ram[32768];
static int lcd_line_busy = 0;
static palette_t palette;	// Colour palette
static uint8_t manual_palette_selected=0;

static struct
{
	unsigned a	: 1;
	unsigned b	: 1;
	unsigned select	: 1;
	unsigned start	: 1;
	unsigned right	: 1;
	unsigned left	: 1;
	unsigned up	: 1;
	unsigned down	: 1;
} prev_joypad_bits;

/* Multicore command structure. */
union core_cmd {
    struct {
	/* Does nothing. */
#define CORE_CMD_NOP		0
	/* Set line "data" on the LCD. Pixel data is in pixels_buffer. */
#define CORE_CMD_LCD_LINE	1
	/* Control idle mode on the LCD. Limits colours to 2 bits. */
#define CORE_CMD_IDLE_SET	2
	/* Set a specific pixel. For debugging. */
#define CORE_CMD_SET_PIXEL	3
	uint8_t cmd;
	uint8_t unused1;
	uint8_t unused2;
	uint8_t data;
    };
    uint32_t full;
};

/* Pixel data is stored in here. */
static uint8_t pixels_buffer[LCD_WIDTH];

#define putstdio(x) write(1, x, strlen(x))

/* Functions required for communication with the ILI9225. */
void mk_ili9225_set_rst(bool state)
{
	gpio_put(GPIO_RST, state);
}

void mk_ili9225_set_rs(bool state)
{
	gpio_put(GPIO_RS, state);
}

void mk_ili9225_set_cs(bool state)
{
	gpio_put(GPIO_CS, state);
}

void mk_ili9225_set_led(bool state)
{
	gpio_put(GPIO_LED, state);
}

void mk_ili9225_spi_write16(const uint16_t *halfwords, size_t len)
{
	spi_write16_blocking(spi0, halfwords, len);
}

void mk_ili9225_delay_ms(unsigned ms)
{
	sleep_ms(ms);
}

/**
 * Returns a byte from the ROM file at the given address.
 */
uint8_t gb_rom_read(struct gb_s *gb, const uint_fast32_t addr)
{
	(void) gb;
	if(addr < sizeof(rom_bank0))
		return rom_bank0[addr];

	return rom[addr];
}

/**
 * Returns a byte from the cartridge RAM at the given address.
 */
uint8_t gb_cart_ram_read(struct gb_s *gb, const uint_fast32_t addr)
{
	(void) gb;
	return ram[addr];
}

/**
 * Writes a given byte to the cartridge RAM at the given address.
 */
void gb_cart_ram_write(struct gb_s *gb, const uint_fast32_t addr,
		       const uint8_t val)
{
	ram[addr] = val;
}

/**
 * Ignore all errors.
 */
void gb_error(struct gb_s *gb, const enum gb_error_e gb_err, const uint16_t addr)
{
#if 1
	const char* gb_err_str[4] = {
			"UNKNOWN",
			"INVALID OPCODE",
			"INVALID READ",
			"INVALID WRITE"
		};
	printf("Error %d occurred: %s at %04X\n.\n", gb_err, gb_err_str[gb_err], addr);
//	abort();
#endif
}

#if ENABLE_LCD 
void core1_lcd_draw_line(const uint_fast8_t line)
{
	static uint16_t fb[LCD_WIDTH];

	for(unsigned int x = 0; x < LCD_WIDTH; x++)
	{
		fb[x] = palette[(pixels_buffer[x] & LCD_PALETTE_ALL) >> 4]
				[pixels_buffer[x] & 3];
	}

	mk_ili9225_set_x(line + 16);
	mk_ili9225_write_pixels(fb, LCD_WIDTH);
	__atomic_store_n(&lcd_line_busy, 0, __ATOMIC_SEQ_CST);
}

_Noreturn
void main_core1(void)
{
	union core_cmd cmd;

	/* Initialise and control LCD on core 1. */
	mk_ili9225_init();

	/* Clear LCD screen. */
	mk_ili9225_fill(0x0000);

	/* Set LCD window to DMG size. */
	mk_ili9225_fill_rect(31,16,LCD_WIDTH,LCD_HEIGHT,0x0000);

	// Sleep used for debugging LCD window.
	//sleep_ms(1000);

	/* Handle commands coming from core0. */
	while(1)
	{
		cmd.full = multicore_fifo_pop_blocking();
		switch(cmd.cmd)
		{
		case CORE_CMD_LCD_LINE:
			core1_lcd_draw_line(cmd.data);
			break;

		case CORE_CMD_IDLE_SET:
			mk_ili9225_display_control(true, cmd.data);
			break;

		case CORE_CMD_NOP:
		default:
			break;
		}
	}

	HEDLEY_UNREACHABLE();
}
#endif

#if ENABLE_LCD
void lcd_draw_line(struct gb_s *gb, const uint8_t pixels[LCD_WIDTH],
		   const uint_fast8_t line)
{
	union core_cmd cmd;

	/* Wait until previous line is sent. */
	while(__atomic_load_n(&lcd_line_busy, __ATOMIC_SEQ_CST))
		tight_loop_contents();

	memcpy(pixels_buffer, pixels, LCD_WIDTH);
	
	/* Populate command. */
	cmd.cmd = CORE_CMD_LCD_LINE;
	cmd.data = line;

	__atomic_store_n(&lcd_line_busy, 1, __ATOMIC_SEQ_CST);
	multicore_fifo_push_blocking(cmd.full);
}
#endif

#if ENABLE_SDCARD
/**
 * Load a save file from the SD card
 */
void read_cart_ram_file(struct gb_s *gb) {
	char filename[16];
	uint_fast32_t save_size;
	UINT br;
	
	gb_get_rom_name(gb,filename);
	save_size=gb_get_save_size(gb);
	if(save_size>0) {
		sd_card_t *pSD=sd_get_by_num(0);
		FRESULT fr=f_mount(&pSD->fatfs,pSD->pcName,1);
		if (FR_OK!=fr) {
			printf("E f_mount error: %s (%d)\n",FRESULT_str(fr),fr);
			return;
		}

		FIL fil;
		fr=f_open(&fil,filename,FA_READ);
		if (fr==FR_OK) {
			f_read(&fil,ram,f_size(&fil),&br);
		} else {
			printf("E f_open(%s) error: %s (%d)\n",filename,FRESULT_str(fr),fr);
		}
		
		fr=f_close(&fil);
		if(fr!=FR_OK) {
			printf("E f_close error: %s (%d)\n", FRESULT_str(fr), fr);
		}
		f_unmount(pSD->pcName);
	}
	printf("I read_cart_ram_file(%s) COMPLETE (%lu bytes)\n",filename,save_size);
}

/**
 * Write a save file to the SD card
 */
void write_cart_ram_file(struct gb_s *gb) {
	char filename[16];
	uint_fast32_t save_size;
	UINT bw;
	
	gb_get_rom_name(gb,filename);
	save_size=gb_get_save_size(gb);
	if(save_size>0) {
		sd_card_t *pSD=sd_get_by_num(0);
		FRESULT fr=f_mount(&pSD->fatfs,pSD->pcName,1);
		if (FR_OK!=fr) {
			printf("E f_mount error: %s (%d)\n",FRESULT_str(fr),fr);
			return;
		}

		FIL fil;
		fr=f_open(&fil,filename,FA_CREATE_ALWAYS | FA_WRITE);
		if (fr==FR_OK) {
			f_write(&fil,ram,save_size,&bw);
		} else {
			printf("E f_open(%s) error: %s (%d)\n",filename,FRESULT_str(fr),fr);
		}
		
		fr=f_close(&fil);
		if(fr!=FR_OK) {
			printf("E f_close error: %s (%d)\n", FRESULT_str(fr), fr);
		}
		f_unmount(pSD->pcName);
	}
	printf("I write_cart_ram_file(%s) COMPLETE (%lu bytes)\n",filename,save_size);
}

/**
 * Load a .gb rom file in flash from the SD card 
 */ 
void load_cart_rom_file(char *filename) {
	UINT br;
	uint8_t buffer[FLASH_SECTOR_SIZE];
	bool mismatch=false;
	sd_card_t *pSD=sd_get_by_num(0);
	FRESULT fr=f_mount(&pSD->fatfs,pSD->pcName,1);
	if (FR_OK!=fr) {
		printf("E f_mount error: %s (%d)\n",FRESULT_str(fr),fr);
		return;
	}
	FIL fil;
	fr=f_open(&fil,filename,FA_READ);
	if (fr==FR_OK) {
		uint32_t flash_target_offset=FLASH_TARGET_OFFSET;
		for(;;) {
			f_read(&fil,buffer,sizeof buffer,&br);
			if(br==0) break; /* end of file */

			printf("I Erasing target region...\n");
			flash_range_erase(flash_target_offset,FLASH_SECTOR_SIZE);
			printf("I Programming target region...\n");
			flash_range_program(flash_target_offset,buffer,FLASH_SECTOR_SIZE);
			
			/* Read back target region and check programming */
			printf("I Done. Reading back target region...\n");
			for(uint32_t i=0;i<FLASH_SECTOR_SIZE;i++) {
				if(rom[flash_target_offset+i]!=buffer[i]) {
					mismatch=true;
				}
			}

			/* Next sector */
			flash_target_offset+=FLASH_SECTOR_SIZE;
		}
		if(mismatch) {
	        printf("I Programming successful!\n");
		} else {
			printf("E Programming failed!\n");
		}
	} else {
		printf("E f_open(%s) error: %s (%d)\n",filename,FRESULT_str(fr),fr);
	}
	
	fr=f_close(&fil);
	if(fr!=FR_OK) {
		printf("E f_close error: %s (%d)\n", FRESULT_str(fr), fr);
	}
	f_unmount(pSD->pcName);

	printf("I load_cart_rom_file(%s) COMPLETE (%lu bytes)\n",filename,br);
}

/**
 * Function used by the rom file selector to display one page of .gb rom files
 */
uint16_t rom_file_selector_display_page(char filename[22][256],uint16_t num_page) {
	sd_card_t *pSD=sd_get_by_num(0);
    DIR dj;
    FILINFO fno;
    FRESULT fr;

    fr=f_mount(&pSD->fatfs,pSD->pcName,1);
    if (FR_OK!=fr) {
        printf("E f_mount error: %s (%d)\n",FRESULT_str(fr),fr);
        return 0;
    }

	/* clear the filenames array */
	for(uint8_t ifile=0;ifile<22;ifile++) {
		strcpy(filename[ifile],"");
	}

    /* search *.gb files */
	uint16_t num_file=0;
	fr=f_findfirst(&dj, &fno, "", "*.gb");

	/* skip the first N pages */
	if(num_page>0) {
		while(num_file<num_page*22 && fr == FR_OK && fno.fname[0]) {
			num_file++;
			fr=f_findnext(&dj, &fno);
		}
	}

	/* store the filenames of this page */
	num_file=0;
    while(num_file<22 && fr == FR_OK && fno.fname[0]) {
		strcpy(filename[num_file],fno.fname);
        num_file++;
        fr=f_findnext(&dj, &fno);
    }
	f_closedir(&dj);
	f_unmount(pSD->pcName);

	/* display *.gb rom files on screen */
	mk_ili9225_fill(0x0000);
	for(uint8_t ifile=0;ifile<num_file;ifile++) {
		mk_ili9225_text(filename[ifile],0,ifile*8,0xFFFF,0x0000);
    }
	return num_file;
}

/**
 * The ROM selector displays pages of up to 22 rom files
 * allowing the user to select which rom file to start
 * Copy your *.gb rom files to the root directory of the SD card
 */
void rom_file_selector() {
    uint16_t num_page;
	char filename[22][256];
	uint16_t num_file;
	
	/* display the first page with up to 22 rom files */
	num_file=rom_file_selector_display_page(filename,num_page);

	/* select the first rom */
	uint8_t selected=0;
	mk_ili9225_text(filename[selected],0,selected*8,0xFFFF,0xF800);

	/* get user's input */
	bool up,down,left,right,a,b,select,start;
	while(true) {
		up=gpio_get(GPIO_UP);
		down=gpio_get(GPIO_DOWN);
		left=gpio_get(GPIO_LEFT);
		right=gpio_get(GPIO_RIGHT);
		a=gpio_get(GPIO_A);
		b=gpio_get(GPIO_B);
		select=gpio_get(GPIO_SELECT);
		start=gpio_get(GPIO_START);
		if(!start) {
			/* re-start the last game (no need to reprogram flash) */
			break;
		}
		if(!a | !b) {
			/* copy the rom from the SD card to flash and start the game */
			load_cart_rom_file(filename[selected]);
			break;
		}
		if(!down) {
			/* select the next rom */
			mk_ili9225_text(filename[selected],0,selected*8,0xFFFF,0x0000);
			selected++;
			if(selected>=num_file) selected=0;
			mk_ili9225_text(filename[selected],0,selected*8,0xFFFF,0xF800);
			sleep_ms(150);
		}
		if(!up) {
			/* select the previous rom */
			mk_ili9225_text(filename[selected],0,selected*8,0xFFFF,0x0000);
			if(selected==0) {
				selected=num_file-1;
			} else {
				selected--;
			}
			mk_ili9225_text(filename[selected],0,selected*8,0xFFFF,0xF800);
			sleep_ms(150);
		}
		if(!right) {
			/* select the next page */
			num_page++;
			num_file=rom_file_selector_display_page(filename,num_page);
			if(num_file==0) {
				/* no files in this page, go to the previous page */
				num_page--;
				num_file=rom_file_selector_display_page(filename,num_page);
			}
			/* select the first file */
			selected=0;
			mk_ili9225_text(filename[selected],0,selected*8,0xFFFF,0xF800);
			sleep_ms(150);
		}
		if((!left) && num_page>0) {
			/* select the previous page */
			num_page--;
			num_file=rom_file_selector_display_page(filename,num_page);
			/* select the first file */
			selected=0;
			mk_ili9225_text(filename[selected],0,selected*8,0xFFFF,0xF800);
			sleep_ms(150);
		}
		tight_loop_contents();
	}
}

#endif

int main(void)
{
	static struct gb_s gb;
	enum gb_init_error_e ret;
	
	/* Overclock. */
	{
		const unsigned vco = 1596*1000*1000;	/* 266MHz */
		const unsigned div1 = 6, div2 = 1;

		vreg_set_voltage(VREG_VOLTAGE_1_15);
		sleep_ms(2);
		set_sys_clock_pll(vco, div1, div2);
		sleep_ms(2);
	}

	/* Initialise USB serial connection for debugging. */
	stdio_init_all();
	time_init();
	// sleep_ms(5000);
	putstdio("INIT: ");

	/* Initialise GPIO pins. */
	gpio_set_function(GPIO_UP, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_DOWN, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_LEFT, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_RIGHT, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_A, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_B, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_SELECT, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_START, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_CS, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_CLK, GPIO_FUNC_SPI);
	gpio_set_function(GPIO_SDA, GPIO_FUNC_SPI);
	gpio_set_function(GPIO_RS, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_RST, GPIO_FUNC_SIO);
	gpio_set_function(GPIO_LED, GPIO_FUNC_SIO);

	gpio_set_dir(GPIO_UP, false);
	gpio_set_dir(GPIO_DOWN, false);
	gpio_set_dir(GPIO_LEFT, false);
	gpio_set_dir(GPIO_RIGHT, false);
	gpio_set_dir(GPIO_A, false);
	gpio_set_dir(GPIO_B, false);
	gpio_set_dir(GPIO_SELECT, false);
	gpio_set_dir(GPIO_START, false);
	gpio_set_dir(GPIO_CS, true);
	gpio_set_dir(GPIO_RS, true);
	gpio_set_dir(GPIO_RST, true);
	gpio_set_dir(GPIO_LED, true);
	gpio_set_slew_rate(GPIO_CLK, GPIO_SLEW_RATE_FAST);
	gpio_set_slew_rate(GPIO_SDA, GPIO_SLEW_RATE_FAST);
	
	gpio_pull_up(GPIO_UP);
	gpio_pull_up(GPIO_DOWN);
	gpio_pull_up(GPIO_LEFT);
	gpio_pull_up(GPIO_RIGHT);
	gpio_pull_up(GPIO_A);
	gpio_pull_up(GPIO_B);
	gpio_pull_up(GPIO_SELECT);
	gpio_pull_up(GPIO_START);

	/* Set SPI clock to use high frequency. */
	clock_configure(clk_peri, 0,
			CLOCKS_CLK_PERI_CTRL_AUXSRC_VALUE_CLK_SYS,
			125 * 1000 * 1000, 125 * 1000 * 1000);
	spi_init(spi0, 30*1000*1000);
	spi_set_format(spi0, 16, SPI_CPOL_0, SPI_CPHA_0, SPI_MSB_FIRST);

#if ENABLE_SOUND
	// Allocate memory for the stream buffer
	stream=malloc(AUDIO_BUFFER_SIZE_BYTES);
    assert(stream!=NULL);
    memset(stream,0,AUDIO_BUFFER_SIZE_BYTES);  // Zero out the stream buffer
	
	// Initialize I2S sound driver
	i2s_config_t i2s_config = i2s_get_default_config();
	i2s_config.sample_freq=AUDIO_SAMPLE_RATE;
	i2s_config.dma_trans_count =AUDIO_SAMPLES;
	i2s_volume(&i2s_config,2);
	i2s_init(&i2s_config);
#endif

while(true)
{
#if ENABLE_LCD
#if ENABLE_SDCARD
	/* ROM File selector */
	mk_ili9225_init();
	mk_ili9225_fill(0x0000);
	rom_file_selector();
#endif
#endif

	/* Initialise GB context. */
	memcpy(rom_bank0, rom, sizeof(rom_bank0));
	ret = gb_init(&gb, &gb_rom_read, &gb_cart_ram_read,
		      &gb_cart_ram_write, &gb_error, NULL);
	putstdio("GB ");

	if(ret != GB_INIT_NO_ERROR)
	{
		printf("Error: %d\n", ret);
		goto out;
	}

	/* Automatically assign a colour palette to the game */
	char rom_title[16];
	auto_assign_palette(palette, gb_colour_hash(&gb),gb_get_rom_name(&gb,rom_title));
	
#if ENABLE_LCD
	gb_init_lcd(&gb, &lcd_draw_line);

	/* Start Core1, which processes requests to the LCD. */
	putstdio("CORE1 ");
	multicore_launch_core1(main_core1);
	
	putstdio("LCD ");
#endif

#if ENABLE_SOUND
	// Initialize audio emulation
	audio_init();
	
	putstdio("AUDIO ");
#endif

#if ENABLE_SDCARD
	/* Load Save File. */
	read_cart_ram_file(&gb);
#endif

	putstdio("\n> ");
	uint_fast32_t frames = 0;
	uint64_t start_time = time_us_64();
	while(1)
	{
		int input;

		gb.gb_frame = 0;

		do {
			__gb_step_cpu(&gb);
			tight_loop_contents();
		} while(HEDLEY_LIKELY(gb.gb_frame == 0));

		frames++;
#if ENABLE_SOUND
		if(!gb.direct.frame_skip) {
			audio_callback(NULL, stream, AUDIO_BUFFER_SIZE_BYTES);
			i2s_dma_write(&i2s_config, stream);
		}
#endif

		/* Update buttons state */
		prev_joypad_bits.up=gb.direct.joypad_bits.up;
		prev_joypad_bits.down=gb.direct.joypad_bits.down;
		prev_joypad_bits.left=gb.direct.joypad_bits.left;
		prev_joypad_bits.right=gb.direct.joypad_bits.right;
		prev_joypad_bits.a=gb.direct.joypad_bits.a;
		prev_joypad_bits.b=gb.direct.joypad_bits.b;
		prev_joypad_bits.select=gb.direct.joypad_bits.select;
		prev_joypad_bits.start=gb.direct.joypad_bits.start;
		gb.direct.joypad_bits.up=gpio_get(GPIO_UP);
		gb.direct.joypad_bits.down=gpio_get(GPIO_DOWN);
		gb.direct.joypad_bits.left=gpio_get(GPIO_LEFT);
		gb.direct.joypad_bits.right=gpio_get(GPIO_RIGHT);
		gb.direct.joypad_bits.a=gpio_get(GPIO_A);
		gb.direct.joypad_bits.b=gpio_get(GPIO_B);
		gb.direct.joypad_bits.select=gpio_get(GPIO_SELECT);
		gb.direct.joypad_bits.start=gpio_get(GPIO_START);

		/* hotkeys (select + * combo)*/
		if(!gb.direct.joypad_bits.select) {
#if ENABLE_SOUND
			if(!gb.direct.joypad_bits.up && prev_joypad_bits.up) {
				/* select + up: increase sound volume */
				i2s_increase_volume(&i2s_config);
			}
			if(!gb.direct.joypad_bits.down && prev_joypad_bits.down) {
				/* select + down: decrease sound volume */
				i2s_decrease_volume(&i2s_config);
			}
#endif
			if(!gb.direct.joypad_bits.right && prev_joypad_bits.right) {
				/* select + right: select the next manual color palette */
				if(manual_palette_selected<12) {
					manual_palette_selected++;
					manual_assign_palette(palette,manual_palette_selected);
				}	
			}
			if(!gb.direct.joypad_bits.left && prev_joypad_bits.left) {
				/* select + left: select the previous manual color palette */
				if(manual_palette_selected>0) {
					manual_palette_selected--;
					manual_assign_palette(palette,manual_palette_selected);
				}
			}
			if(!gb.direct.joypad_bits.start && prev_joypad_bits.start) {
				/* select + start: save ram and resets to the game selection menu */
#if ENABLE_SDCARD				
				write_cart_ram_file(&gb);
#endif				
				goto out;
			}
			if(!gb.direct.joypad_bits.a && prev_joypad_bits.a) {
				/* select + A: enable/disable frame-skip => fast-forward */
				gb.direct.frame_skip=!gb.direct.frame_skip;
				printf("I gb.direct.frame_skip = %d\n",gb.direct.frame_skip);
			}
		}

		/* Serial monitor commands */ 
		input = getchar_timeout_us(0);
		if(input == PICO_ERROR_TIMEOUT)
			continue;

		switch(input)
		{
#if 0
		static bool invert = false;
		static bool sleep = false;
		static uint8_t freq = 1;
		static ili9225_color_mode_e colour = ILI9225_COLOR_MODE_FULL;

		case 'i':
			invert = !invert;
			mk_ili9225_display_control(invert, colour);
			break;

		case 'f':
			freq++;
			freq &= 0x0F;
			mk_ili9225_set_drive_freq(freq);
			printf("Freq %u\n", freq);
			break;
#endif
		case 'c':
		{
			static ili9225_color_mode_e mode = ILI9225_COLOR_MODE_FULL;
			union core_cmd cmd;

			mode = !mode;
			cmd.cmd = CORE_CMD_IDLE_SET;
			cmd.data = mode;
			multicore_fifo_push_blocking(cmd.full);
			break;
		}

		case 'i':
			gb.direct.interlace = !gb.direct.interlace;
			break;

		case 'f':
			gb.direct.frame_skip = !gb.direct.frame_skip;
			break;

		case 'b':
		{
			uint64_t end_time;
			uint32_t diff;
			uint32_t fps;

			end_time = time_us_64();
			diff = end_time-start_time;
			fps = ((uint64_t)frames*1000*1000)/diff;
			printf("Frames: %u\n"
				"Time: %lu us\n"
				"FPS: %lu\n",
				frames, diff, fps);
			stdio_flush();
			frames = 0;
			start_time = time_us_64();
			break;
		}

		case '\n':
		case '\r':
		{
			gb.direct.joypad_bits.start = 0;
			break;
		}

		case '\b':
		{
			gb.direct.joypad_bits.select = 0;
			break;
		}

		case '8':
		{
			gb.direct.joypad_bits.up = 0;
			break;
		}

		case '2':
		{
			gb.direct.joypad_bits.down = 0;
			break;
		}

		case '4':
		{
			gb.direct.joypad_bits.left= 0;
			break;
		}

		case '6':
		{
			gb.direct.joypad_bits.right = 0;
			break;
		}

		case 'z':
		case 'w':
		{
			gb.direct.joypad_bits.a = 0;
			break;
		}

		case 'x':
		{
			gb.direct.joypad_bits.b = 0;
			break;
		}

		case 'q':
			goto out;

		default:
			break;
		}
	}
out:
	puts("\nEmulation Ended");
	/* stop lcd task running on core 1 */
	multicore_reset_core1(); 

}

}