/**********************************************************/
/* Serial Bootloader for Atmel megaAVR Controllers        */
/*                                                        */
/* tested with ATmega644 and ATmega644P                   */
/* should work with other mega's, see code for details    */
/*                                                        */
/* ATmegaBOOT.c                                           */
/*                                                        */
/* 20090131: Added 324P support from Alex Leone           */
/*           Marius Kintel                                */
/* 20080915: applied ADABoot mods for Sanguino 644P       */
/*           Brian Riley                                  */
/* 20080711: hacked for Sanguino by Zach Smith            */
/*           and Justin Day                               */
/* 20070626: hacked for Arduino Diecimila (which auto-    */
/*           resets when a USB connection is made to it)  */
/*           by D. Mellis                                 */
/* 20060802: hacked for Arduino by D. Cuartielles         */
/*           based on a previous hack by D. Mellis        */
/*           and D. Cuartielles                           */
/*                                                        */
/* Monitor and debug functions were added to the original */
/* code by Dr. Erik Lins, chip45.com. (See below)         */
/*                                                        */
/* Thanks to Karl Pitrich for fixing a bootloader pin     */
/* problem and more informative LED blinking!             */
/*                                                        */
/* For the latest version see:                            */
/* http://www.chip45.com/                                 */
/*                                                        */
/* ------------------------------------------------------ */
/*                                                        */
/* based on stk500boot.c                                  */
/* Copyright (c) 2003, Jason P. Kyle                      */
/* All rights reserved.                                   */
/* see avr1.org for original file and information         */
/*                                                        */
/* This program is free software; you can redistribute it */
/* and/or modify it under the terms of the GNU General    */
/* Public License as published by the Free Software       */
/* Foundation; either version 2 of the License, or        */
/* (at your option) any later version.                    */
/*                                                        */
/* This program is distributed in the hope that it will   */
/* be useful, but WITHOUT ANY WARRANTY; without even the  */
/* implied warranty of MERCHANTABILITY or FITNESS FOR A   */
/* PARTICULAR PURPOSE.  See the GNU General Public        */
/* License for more details.                              */
/*                                                        */
/* You should have received a copy of the GNU General     */
/* Public License along with this program; if not, write  */
/* to the Free Software Foundation, Inc.,                 */
/* 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA */
/*                                                        */
/* Licence can be viewed at                               */
/* http://www.fsf.org/licenses/gpl.txt                    */
/*                                                        */
/* Target = Atmel AVR m128,m64,m32,m16,m8,m162,m163,m169, */
/* m8515,m8535. ATmega161 has a very small boot block so  */
/* isn't supported.                                       */
/*                                                        */
/* Tested with m168                                       */
/**********************************************************/

/* $Id$ */


/* some includes */
#include <inttypes.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/interrupt.h>
#include <avr/wdt.h>
#include <avr/boot.h>

#ifdef ADABOOT
    #define NUM_LED_FLASHES 3
    #define ADABOOT_VER	1
#endif


/* 20070707: hacked by David A. Mellis - after this many errors give up and launch application */
#define MAX_ERROR_COUNT 5

/* set the UART baud rate */
/* 20080711: hack by Zach Hoeken */
#define BAUD_RATE   38400

/* SW_MAJOR and MINOR needs to be updated from time to time to avoid warning message from AVR Studio */
/* never allow AVR Studio to do an update !!!! */
#define HW_VER	 0x02
#define SW_MAJOR 0x01
#define SW_MINOR 0x10

/* onboard LED is used to indicate, that the bootloader was entered (3x flashing) */
/* if monitor functions are included, LED goes on after monitor was entered */
#define LED_DDR  DDRB
#define LED_PORT PORTB
#define LED_PIN  PINB
#define LED      PINB0

/* define various device id's */
/* manufacturer byte is always the same */
#define SIG1	0x1E	// Yep, Atmel is the only manufacturer of AVR micros.  Single source :(
#if defined(__AVR_ATmega1284P__)
#define SIG2	0x97
#define SIG3	0x05
#elif defined(__AVR_ATmega644P__)
#define SIG2	0x96
#define SIG3	0x0A
#elif defined(__AVR_ATmega644__)
#define SIG2	0x96
#define SIG3	0x09
#elif defined(__AVR_ATmega324P__)
#define SIG2	0x95
#define SIG3	0x08
#endif

#define PAGE_SIZE		0x080U   //128 words
#define PAGE_SIZE_BYTES	0x100U   //256 bytes

/* function prototypes */
void putch(char);
char getch(void);
void getNch(uint8_t);
void byte_response(uint8_t);
void nothing_response(void);
char gethex(void);
void puthex(char);
void flash_led(uint8_t);

/* some variables */
union address_union
{
    uint16_t word;
    uint8_t  byte[2];
} address;

union length_union
{
    uint16_t word;
    uint8_t  byte[2];
} length;

struct flags_struct
{
    unsigned eeprom : 1;
    unsigned rampz  : 1;
} flags;

uint8_t buff[256];

uint8_t error_count = 0;
uint8_t sreg;

void (*app_start)(void) = 0x0000;

/* main program starts here */
int main(void)
{
    uint8_t ch,ch2;
    uint16_t w;
	uint16_t i;
	
    asm volatile("nop\n\t");

#ifdef ADABOOT		// BBR/LF 10/8/2007 & 9/13/2008
    ch = MCUSR;
    MCUSR = 0;

    WDTCSR |= _BV(WDCE) | _BV(WDE);
    WDTCSR = 0;

    // Check if the WDT was used to reset, in which case we dont bootload and skip straight to the code. woot.
    if (! (ch &  _BV(EXTRF))) // if it's a not an external reset...
      app_start();  // skip bootloader
#endif


	//initialize our serial port.
    UBRR0L = (uint8_t)(F_CPU/(BAUD_RATE*16L)-1);
    UBRR0H = (F_CPU/(BAUD_RATE*16L)-1) >> 8;
    UCSR0B = (1<<RXEN0) | (1<<TXEN0);
    UCSR0C = (1<<UCSZ00) | (1<<UCSZ01);

    /* Enable internal pull-up resistor on pin D0 (RX), in order
    to supress line noise that prevents the bootloader from
    timing out (DAM: 20070509) */
    DDRD &= ~_BV(PIND0);
    PORTD |= _BV(PIND0);

    /* set LED pin as output */
    LED_DDR |= _BV(LED);

	    /* flash onboard LED to signal entering of bootloader                   */
	    /* ADABOOT will do two series of flashes. first 4 - signifying ADABOOT  */
	    /* then a pause and another flash series signifying ADABOOT sub-version */


	flash_led(NUM_LED_FLASHES);

	#ifdef	ADABOOT
		flash_led(ADABOOT_VER);		// BBR 9/13/2008
	#endif 

    /* forever loop */
    for (;;)
	{
		/* get character from UART */
		ch = getch();

		/* A bunch of if...else if... gives smaller code than switch...case ! */

		/* Hello is anyone home ? */ 
		if(ch=='0')
		    nothing_response();


		/* Request programmer ID */
		/* Not using PROGMEM string due to boot block in m128 being beyond 64kB boundry  */
		/* Would need to selectively manipulate RAMPZ, and it's only 9 characters anyway so who cares.  */
		else if(ch=='1')
		{
		    if (getch() == ' ')
			{
				putch(0x14);
				putch('A');
				putch('V');
				putch('R');
				putch(' ');
				putch('I');
				putch('S');
				putch('P');
				putch(0x10);
		    }
			else
			{
				if (++error_count == MAX_ERROR_COUNT)
				    app_start();
		    }
		}


		/* AVR ISP/STK500 board commands  DON'T CARE so default nothing_response */
		else if(ch=='@')
		{
		    ch2 = getch();
		    if (ch2 > 0x85)
				getch();
		    nothing_response();
		}


		/* AVR ISP/STK500 board requests */
		else if(ch=='A')
		{
		    ch2 = getch();
		    if(ch2 == 0x80)
				byte_response(HW_VER);		// Hardware version
		    else if(ch2==0x81)
				byte_response(SW_MAJOR);	// Software major version
		    else if(ch2==0x82)
				byte_response(SW_MINOR);	// Software minor version
		    else if(ch2==0x98)
				byte_response(0x03);		// Unknown but seems to be required by avr studio 3.56
		    else
				byte_response(0x00);		// Covers various unnecessary responses we don't care about
		}


		/* Device Parameters  DON'T CARE, DEVICE IS FIXED  */
		else if(ch=='B')
		{
		    getNch(20);
		    nothing_response();
		}


		/* Parallel programming stuff  DON'T CARE  */
		else if(ch=='E')
		{
		    getNch(5);
		    nothing_response();
		}


		/* Enter programming mode  */
		else if(ch=='P')
		{
		    nothing_response();
		}


		/* Leave programming mode  */
		else if(ch=='Q')
		{
		    nothing_response();
#ifdef ADABOOT		
			// autoreset via watchdog (sneaky!) BBR/LF 9/13/2008
	  		WDTCSR = _BV(WDE);
	  		while (1); // 16 ms
#endif		
		}


		/* Erase device, don't care as we will erase one page at a time anyway.  */
		else if(ch=='R')
		{
		    nothing_response();
		}


		/* Set address, little endian. EEPROM in bytes, FLASH in words  */
		/* Perhaps extra address bytes may be added in future to support > 128kB FLASH.  */
		/* This might explain why little endian was used here, big endian used everywhere else.  */
		else if(ch=='U')
		{
		    address.byte[0] = getch();
		    address.byte[1] = getch();
		    nothing_response();
		}


		/* Universal SPI programming command, disabled.  Would be used for fuses and lock bits.  */
		else if(ch=='V')
		{
		    getNch(4);
		    byte_response(0x00);
		}


		/* Write memory, length is big endian and is in bytes  */
		else if(ch=='d')
		{
		    length.byte[1] = getch();
		    length.byte[0] = getch();
	
		    flags.eeprom = 0;
		    if (getch() == 'E')
				flags.eeprom = 1;

			for (i=0; i<PAGE_SIZE; i++)
				buff[i] = 0;
		
		    for (w = 0; w < length.word; w++)
			{
				// Store data in buffer, can't keep up with serial data stream whilst programming pages
				buff[w] = getch();
		    }
	
		    if (getch() == ' ')
			{
				if (flags.eeprom)
				{		                
					//Write to EEPROM one byte at a time
				    for(w=0;w<length.word;w++)
					{
						while(EECR & (1<<EEPE));
					
						EEAR = (uint16_t)(void *)address.word;
						EEDR = buff[w];
						EECR |= (1<<EEMPE);
						EECR |= (1<<EEPE);

						address.word++;
				    }			
				}
				else
				{
					//address * 2 -> byte location
				    address.word = address.word << 1;
			    
					//Even up an odd number of bytes
					if ((length.byte[0] & 0x01))
						length.word++;
				
					// HACKME: EEPE used to be EEWE
				    //Wait for previous EEPROM writes to complete
					//while(bit_is_set(EECR,EEPE));
					while(EECR & (1<<EEPE));
				
				    asm volatile(
						 "clr	r17		\n\t"	//page_word_count
						 "lds	r30,address	\n\t"	//Address of FLASH location (in bytes)
						 "lds	r31,address+1	\n\t"
						 "ldi	r28,lo8(buff)	\n\t"	//Start of buffer array in RAM
						 "ldi	r29,hi8(buff)	\n\t"
						 "lds	r24,length	\n\t"	//Length of data to be written (in bytes)
						 "lds	r25,length+1	\n\t"
						 "length_loop:		\n\t"	//Main loop, repeat for number of words in block							 							 
						 "cpi	r17,0x00	\n\t"	//If page_word_count=0 then erase page
						 "brne	no_page_erase	\n\t"						 
						 "wait_spm1:		\n\t"
						 "lds	r16,%0		\n\t"	//Wait for previous spm to complete
						 "andi	r16,1           \n\t"
						 "cpi	r16,1           \n\t"
						 "breq	wait_spm1       \n\t"
						 "ldi	r16,0x03	\n\t"	//Erase page pointed to by Z
						 "sts	%0,r16		\n\t"
						 "spm			\n\t"							 
						 "wait_spm2:		\n\t"
						 "lds	r16,%0		\n\t"	//Wait for previous spm to complete
						 "andi	r16,1           \n\t"
						 "cpi	r16,1           \n\t"
						 "breq	wait_spm2       \n\t"									 

						 "ldi	r16,0x11	\n\t"	//Re-enable RWW section
						 "sts	%0,r16		\n\t"						 			 
						 "spm			\n\t"
						 "no_page_erase:		\n\t"							 
						 "ld	r0,Y+		\n\t"	//Write 2 bytes into page buffer
						 "ld	r1,Y+		\n\t"							 
							 
						 "wait_spm3:		\n\t"
						 "lds	r16,%0		\n\t"	//Wait for previous spm to complete
						 "andi	r16,1           \n\t"
						 "cpi	r16,1           \n\t"
						 "breq	wait_spm3       \n\t"
						 "ldi	r16,0x01	\n\t"	//Load r0,r1 into FLASH page buffer
						 "sts	%0,r16		\n\t"
						 "spm			\n\t"
							 
						 "inc	r17		\n\t"	//page_word_count++
						 "cpi r17,%1	        \n\t"
						 "brlo	same_page	\n\t"	//Still same page in FLASH
						 "write_page:		\n\t"
						 "clr	r17		\n\t"	//New page, write current one first
						 "wait_spm4:		\n\t"
						 "lds	r16,%0		\n\t"	//Wait for previous spm to complete
						 "andi	r16,1           \n\t"
						 "cpi	r16,1           \n\t"
						 "breq	wait_spm4       \n\t"						 							 
						 "ldi	r16,0x05	\n\t"	//Write page pointed to by Z
						 "sts	%0,r16		\n\t"
						 "spm			\n\t"
						 "wait_spm5:		\n\t"
						 "lds	r16,%0		\n\t"	//Wait for previous spm to complete
						 "andi	r16,1           \n\t"
						 "cpi	r16,1           \n\t"
						 "breq	wait_spm5       \n\t"									 
						 "ldi	r16,0x11	\n\t"	//Re-enable RWW section
						 "sts	%0,r16		\n\t"						 			 
						 "spm			\n\t"					 		 
						 "same_page:		\n\t"							 
						 "adiw	r30,2		\n\t"	//Next word in FLASH
						 "sbiw	r24,2		\n\t"	//length-2
						 "breq	final_write	\n\t"	//Finished
						 "rjmp	length_loop	\n\t"
						 "final_write:		\n\t"
						 "cpi	r17,0		\n\t"
						 "breq	block_done	\n\t"
						 "adiw	r24,2		\n\t"	//length+2, fool above check on length after short page write
						 "rjmp	write_page	\n\t"
						 "block_done:		\n\t"
						 "clr	__zero_reg__	\n\t"	//restore zero register
						 : "=m" (SPMCSR) : "M" (PAGE_SIZE) : "r0","r16","r17","r24","r25","r28","r29","r30","r31"

						 );
				}
				putch(0x14);
				putch(0x10);
		    }
			else
			{
				if (++error_count == MAX_ERROR_COUNT)
				    app_start();
		    }		
		}
    
		/* Read memory block mode, length is big endian.  */
		else if(ch=='t')
		{
			length.byte[1] = getch();
			length.byte[0] = getch();

			if (getch() == 'E')
				flags.eeprom = 1;
			else
			{
				flags.eeprom = 0;
				address.word = address.word << 1;	        // address * 2 -> byte location
			}

			// Command terminator
			if (getch() == ' ')
			{
				putch(0x14);
				for (w=0; w<length.word; w++)
				{
					// Can handle odd and even lengths okay
				    if (flags.eeprom) 
					{
						// Byte access EEPROM read
						while(EECR & (1<<EEPE));
						EEAR = (uint16_t)(void *)address.word;
						EECR |= (1<<EERE);
						putch(EEDR);

						address.word++;
				    }
				    else
					{
						if (!flags.rampz)
							putch(pgm_read_byte_near(address.word));

						address.word++;
				    }
				}
				putch(0x10);
		    }
		}


		/* Get device signature bytes  */
		else if(ch=='u')
		{
			if (getch() == ' ')
			{
				putch(0x14);
				putch(SIG1);
				putch(SIG2);
				putch(SIG3);
				putch(0x10);
			}
			else
			{
				if (++error_count == MAX_ERROR_COUNT)
					app_start();
			}
		}


		/* Read oscillator calibration byte */
		else if(ch=='v')
			byte_response(0x00);

		else if (++error_count == MAX_ERROR_COUNT)
		    app_start();

	}
    /* end of forever loop */
}


char gethex(void)
{
    char ah,al;

    ah = getch();
	putch(ah);
    al = getch();
	putch(al);
    
	if(ah >= 'a')
		ah = ah - 'a' + 0x0a;
	else if(ah >= '0')
		ah -= '0';
    if(al >= 'a')
		al = al - 'a' + 0x0a;
	else if(al >= '0')
		al -= '0';

    return (ah << 4) + al;
}


void puthex(char ch)
{
    char ah,al;

    ah = (ch & 0xf0) >> 4;
	if(ah >= 0x0a)
		ah = ah - 0x0a + 'a';
	else
		ah += '0';

    al = (ch & 0x0f);
	if(al >= 0x0a)
		al = al - 0x0a + 'a';
	else
		al += '0';

    putch(ah);
    putch(al);
}


void putch(char ch)
{
    while (!(UCSR0A & _BV(UDRE0)));
    UDR0 = ch;
}




char getch(void)
{
    uint32_t count = 0;

#ifdef ADABOOT
	LED_PORT &= ~_BV(LED);          // toggle LED to show activity - BBR/LF 10/3/2007 & 9/13/2008
#endif

    while(!(UCSR0A & _BV(RXC0)))
	{
    	/* 20060803 DojoCorp:: Addon coming from the previous Bootloader*/               
    	/* HACKME:: here is a good place to count times*/
    	count++;
    	if (count > MAX_TIME_COUNT)
    		app_start();
     }

#ifdef ADABOOT
	LED_PORT |= _BV(LED);          // toggle LED to show activity - BBR/LF 10/3/2007 & 9/13/2008
#endif

    return UDR0;
}


void getNch(uint8_t count)
{
    uint8_t i;
    for(i=0;i<count;i++)
	{
		while(!(UCSR0A & _BV(RXC0)));
		UDR0;
    }
}


void byte_response(uint8_t val)
{
    if (getch() == ' ')
	{
		putch(0x14);
		putch(val);
		putch(0x10);
    }
	else
	{
		if (++error_count == MAX_ERROR_COUNT)
		    app_start();
    }
}


void nothing_response(void)
{
    if (getch() == ' ')
	{
		putch(0x14);
		putch(0x10);
    }
	else
	{
		if (++error_count == MAX_ERROR_COUNT)
		    app_start();
    }
}

#ifdef ADABOOT

void flash_led(uint8_t count)
{
    /* flash onboard LED count times to signal entering of bootloader */
	/* l needs to be volatile or the delay loops below might get      */
	/* optimized away if compiling with optimizations (DAM).          */
	
    volatile uint32_t l;

    if (count == 0) {
      count = ADABOOT;
    }
    

	int8_t i;
    for (i = 0; i < count; ++i) {
		LED_PORT |= _BV(LED);					// LED on
		for(l = 0; l < (F_CPU / 1000); ++l);		// delay NGvalue was 1000 for both loops - BBR
		LED_PORT &= ~_BV(LED);					// LED off
		for(l = 0; l < (F_CPU / 250); ++l);		// delay asymmteric for ADA BOOT BBR 
	}

	for(l = 0; l < (F_CPU / 100); ++l);		    // pause ADA BOOT BBR 
		
}

#else

void flash_led(uint8_t count)
{
    /* flash onboard LED three times to signal entering of bootloader */
	/* l needs to be volatile or the delay loops below might get
	optimized away if compiling with optimizations (DAM). */
    volatile uint32_t l;

    if (count == 0) {
      count = 3;
    }
    
	int8_t i;
    for (i = 0; i < count; ++i) {
		LED_PORT |= _BV(LED);
		for(l = 0; l < (F_CPU / 1000); ++l);
		LED_PORT &= ~_BV(LED);
		for(l = 0; l < (F_CPU / 1000); ++l); 
	}
		
}


#endif


/* end of file ATmegaBOOT.c */
