/**********************************************************/
/* Serial Bootloader for Atmel mega8 AVR Controller       */
/*                                                        */
/* ATmegaBOOT.c                                           */
/*                                                        */
/* Copyright (c) 2003, Jason P. Kyle                      */
/*                                                        */
/* Hacked by DojoCorp - ZGZ - MMX - IVR                   */
/* Hacked by David A. Mellis                              */
/* Hacked by Markus Koch                                  */
/*                                                        */
/* 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 m8                                  */
/**********************************************************/

#include <inttypes.h>
#include <avr/io.h>
#include <avr/pgmspace.h>
#include <avr/eeprom.h>
#include <avr/interrupt.h>
#include <util/delay.h>

#define MAX_TIME_COUNT (F_CPU>>1)

/* SW_MAJOR and MINOR needs to be updated from time to time to avoid warning message from AVR Studio */
#define HW_VER	 0x02
#define SW_MAJOR 0x01
#define SW_MINOR 0x12

// AVR-GCC compiler compatibility
// avr-gcc compiler v3.1.x and older doesn't support outb() and inb()
//      if necessary, convert outb and inb to outp and inp
#ifndef outb
#define outb(sfr,val)  (_SFR_BYTE(sfr) = (val))
#endif
#ifndef inb
#define inb(sfr) _SFR_BYTE(sfr)
#endif

/* defines for future compatibility */
#ifndef cbi
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#endif
#ifndef sbi
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#endif

/* Adjust to suit whatever pin your hardware uses to enter the bootloader */
#define eeprom_rb(addr)   eeprom_read_byte ((uint8_t *)(addr))
#define eeprom_rw(addr)   eeprom_read_word ((uint16_t *)(addr))
#define eeprom_wb(addr, val)   eeprom_write_byte ((uint8_t *)(addr), (uint8_t)(val))


#define SIG1	0x1E	// Yep, Atmel is the only manufacturer of AVR micros.  Single source :(
#define SIG2	0x93
#define SIG3	0x07
#define PAGE_SIZE	0x20U	//32 words


void putch(char);
char getch(void);
void getNch(uint8_t);
void byte_response(uint8_t);
void nothing_response(void);

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 address_high;

uint8_t pagesz=0x80;

uint8_t i;
//uint8_t bootuart0=0,bootuart1=0;


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

int main(void)
{
	uint8_t ch,ch2;
	uint16_t w;

	/* Disable interrupts */
	cli();

	/* Pre-init I/O */
	DDRB = 0;
	DDRC = 0;
	DDRD = 0;
	PORTB = 0;
	PORTC = 0;
	PORTD = 0;

	asm volatile("nop\n\t");

	/* initialize UART(s) depending on CPU defined */
	/* m8 */
	UBRRH = (((F_CPU/BAUD_RATE)/16)-1)>>8; 	// set baud rate
	UBRRL = (((F_CPU/BAUD_RATE)/16)-1);
	UCSRB = (1<<RXEN)|(1<<TXEN);  // enable Rx & Tx
	UCSRC = (1<<URSEL)|(1<<UCSZ1)|(1<<UCSZ0);  // config USART; 8N1

	for (i = 0; i < 16; i++) {
		_delay_loop_2(0);
	}

	/* forever */
	for (;;) {
		//if ((inb(UCSRA) & _BV(RXC))){
		/* 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);
			}
		}

		/* 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();
			// FIXME: modified only here by DojoCorp, Mumbai, India, 20050626
			//time_count=0; // exted the delay once entered prog.mode
		}

		/* Leave programming mode  */
		else if (ch == 'Q') {
			nothing_response();
			//time_count=MAX_TIME_COUNT_MORATORY; 	// once the programming is done,
			// we should start the application
			// but uisp has problems with this,
			// therefore we just change the times
			// and give the programmer 1 sec to react
		}

		/* Loop UART until reset */
		else if (ch == 'X') {
			while (1) {
				if (UCSRA & (1 << RXC)) {
					UDR = UDR;
				}
			}
		}

		/* Start user code NOW */
		else if (ch == 'Z') {
			app_start();
		}

		/* 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 (w=0; w<length.word; w++) {
				buff[w] = getch();	                        // Store data in buffer, can't keep up with serial data stream whilst programming pages
			}
			if (getch() == ' ') {
				if (flags.eeprom) {		                //Write to EEPROM one byte at a time
					for(w=0;w<length.word;w++) {
						eeprom_wb(address.word,buff[w]);
						address.word++;
					}
				} else {					        //Write to FLASH one page at a time
					cli();					//Disable interrupts, just to be sure
					while(bit_is_set(EECR,EEWE));			//Wait for previous EEPROM writes to complete
					asm volatile(
					                        "clr	r17		\n\t"	//page_word_count
					                        "lds	r30,address	\n\t"	//Address of FLASH location (in words)
					                        "lds	r31,address+1	\n\t"
					                        "lsl r30				\n\t"  //address * 2 -> byte location
					                        "rol r31				\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"
					                        "sbrs r24,0		\n\t"  //Even up an odd number of bytes
					                        "rjmp length_loop		\n\t"
					                        "adiw r24,1		\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"
					                        "rcall  wait_spm		\n\t"

					                        "ldi	r16,0x03	\n\t"	//Erase page pointed to by Z
					                        "sts	%0,r16		\n\t"
					                        "spm			\n\t"
					                        "rcall  wait_spm		\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"

					                        "rcall  wait_spm		\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
					                        "rcall  wait_spm		\n\t"

					                        "ldi	r16,0x05	\n\t"	//Write page pointed to by Z
					                        "sts	%0,r16		\n\t"
					                        "spm			\n\t"
					                        "rcall  wait_spm		\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"

					                        "wait_spm:  \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_spm       \n\t"
					                        "ret			\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" (SPMCR) : "M" (PAGE_SIZE) : "r0","r16","r17","r24","r25","r28","r29","r30","r31");

					/* Should really add a wait for RWW section to be enabled, don't actually need it since we never */
					/* exit the bootloader without a power cycle anyhow */
				}
				putch(0x14);
				putch(0x10);
			}
		}

		/* 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
			}
			if (getch() == ' ') {		                // Command terminator
				putch(0x14);
				for (w=0; w < length.word; w++) {		        // Can handle odd and even lengths okay
					if (flags.eeprom) {	                        // Byte access EEPROM read
						putch(eeprom_rb(address.word));
						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);
			}
		}

		/* Read oscillator calibration byte */
		else if (ch == 'v') {
			byte_response(0x00);
		}
	} /* end of forever loop */
}

void putch(char ch)
{
	/* m8 */
	while (!(inb(UCSRA) & _BV(UDRE)));
	outb(UDR,ch);
}

char getch(void)
{
	/* m8 */
	uint32_t count = 0;
	while(!(inb(UCSRA) & _BV(RXC))) {
		/* HACKME:: here is a good place to count times*/
		count++;
		if (count > MAX_TIME_COUNT)
			app_start();
	}
	return (inb(UDR));
}

void getNch(uint8_t count)
{
	uint8_t i;
	for(i=0;i<count;i++) {
		getch(); // need to handle time out
	}
}

void byte_response(uint8_t val)
{
	if (getch() == ' ') {
		putch(0x14);
		putch(val);
		putch(0x10);
	}
}

void nothing_response(void)
{
	if (getch() == ' ') {
		putch(0x14);
		putch(0x10);
	}
}