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/**********************************************************/
/* Optiboot bootloader for Arduino */
/* */
/* http://optiboot.googlecode.com */
/* */
/* Arduino-maintained version : See README.TXT */
/* http://code.google.com/p/arduino/ */
/* */
/* Heavily optimised bootloader that is faster and */
/* smaller than the Arduino standard bootloader */
/* */
/* Enhancements: */
/* Fits in 512 bytes, saving 1.5K of code space */
/* Background page erasing speeds up programming */
/* Higher baud rate speeds up programming */
/* Written almost entirely in C */
/* Customisable timeout with accurate timeconstant */
/* Optional virtual UART. No hardware UART required. */
/* Optional virtual boot partition for devices without. */
/* */
/* What you lose: */
/* Implements a skeleton STK500 protocol which is */
/* missing several features including EEPROM */
/* programming and non-page-aligned writes */
/* High baud rate breaks compatibility with standard */
/* Arduino flash settings */
/* */
/* Fully supported: */
/* ATmega168 based devices (Diecimila etc) */
/* ATmega328P based devices (Duemilanove etc) */
/* */
/* Alpha test */
/* ATmega1280 based devices (Arduino Mega) */
/* */
/* Work in progress: */
/* ATmega644P based devices (Sanguino) */
/* ATtiny84 based devices (Luminet) */
/* */
/* Does not support: */
/* USB based devices (eg. Teensy) */
/* */
/* Assumptions: */
/* The code makes several assumptions that reduce the */
/* code size. They are all true after a hardware reset, */
/* but may not be true if the bootloader is called by */
/* other means or on other hardware. */
/* No interrupts can occur */
/* UART and Timer 1 are set to their reset state */
/* SP points to RAMEND */
/* */
/* Code builds on code, libraries and optimisations from: */
/* stk500boot.c by Jason P. Kyle */
/* Arduino bootloader http://arduino.cc */
/* Spiff's 1K bootloader http://spiffie.org/know/arduino_1k_bootloader/bootloader.shtml */
/* avr-libc project http://nongnu.org/avr-libc */
/* Adaboot http://www.ladyada.net/library/arduino/bootloader.html */
/* AVR305 Atmel Application Note */
/* */
/* 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 */
/* */
/**********************************************************/


/**********************************************************/
/* */
/* Optional defines: */
/* */
/**********************************************************/
/* */
/* BIG_BOOT: */
/* Build a 1k bootloader, not 512 bytes. This turns on */
/* extra functionality. */
/* */
/* BAUD_RATE: */
/* Set bootloader baud rate. */
/* */
/* LUDICROUS_SPEED: */
/* 230400 baud :-) */
/* */
/* SOFT_UART: */
/* Use AVR305 soft-UART instead of hardware UART. */
/* */
/* LED_START_FLASHES: */
/* Number of LED flashes on bootup. */
/* */
/* LED_DATA_FLASH: */
/* Flash LED when transferring data. For boards without */
/* TX or RX LEDs, or for people who like blinky lights. */
/* */
/* SUPPORT_EEPROM: */
/* Support reading and writing from EEPROM. This is not */
/* used by Arduino, so off by default. */
/* */
/* TIMEOUT_MS: */
/* Bootloader timeout period, in milliseconds. */
/* 500,1000,2000,4000,8000 supported. */
/* */
/**********************************************************/

/**********************************************************/
/* Version Numbers! */
/* */
/* Arduino Optiboot now includes this Version number in */
/* the source and object code. */
/* */
/* Version 3 was released as zip from the optiboot */
/* repository and was distributed with Arduino 0022. */
/* Version 4 starts with the arduino repository commit */
/* that brought the arduino repository up-to-date with */
/* the optiboot source tree changes since v3. */
/* */
/**********************************************************/

/**********************************************************/
/* Edit History: */
/* */
/* 4.4 WestfW: add initialization of address to keep */
/* the compiler happy. Change SC'ed targets. */
/* Return the SW version via READ PARAM */
/* 4.3 WestfW: catch framing errors in getch(), so that */
/* AVRISP works without HW kludges. */
/* http://code.google.com/p/arduino/issues/detail?id=368n*/
/* 4.2 WestfW: reduce code size, fix timeouts, change */
/* verifySpace to use WDT instead of appstart */
/* 4.1 WestfW: put version number in binary. */
/**********************************************************/

#define OPTIBOOT_MAJVER 4
#define OPTIBOOT_MINVER 4

#define MAKESTR(a) #a
#define MAKEVER(a, b) MAKESTR(a*256+b)

asm(" .section .version\n"
    "optiboot_version: .word " MAKEVER(OPTIBOOT_MAJVER, OPTIBOOT_MINVER) "\n"
    " .section .text\n");
#include <inttypes.h>
#include <avr/io.h>
#include <avr/pgmspace.h>

// <avr/boot.h> uses sts instructions, but this version uses out instructions
// This saves cycles and program memory.
#include "boot.h"


// We don't use <avr/wdt.h> as those routines have interrupt overhead we don't need.

#include "pin_defs.h"
#include "stk500.h"

#ifndef LED_START_FLASHES
#define LED_START_FLASHES 0
#endif

#ifdef LUDICROUS_SPEED
#define BAUD_RATE 230400L
#endif

/* set the UART baud rate defaults */
#ifndef BAUD_RATE
#if F_CPU >= 8000000L
#define BAUD_RATE 115200L // Highest rate Avrdude win32 will support
#elsif F_CPU >= 1000000L
#define BAUD_RATE 9600L // 19200 also supported, but with significant error
#elsif F_CPU >= 128000L
#define BAUD_RATE 4800L // Good for 128kHz internal RC
#else
#define BAUD_RATE 1200L // Good even at 32768Hz
#endif
#endif

/* Switch in soft UART for hard baud rates */
#if (F_CPU/BAUD_RATE) > 280 // > 57600 for 16MHz
#ifndef SOFT_UART
#define SOFT_UART
#endif
#endif

/* Watchdog settings */
#define WATCHDOG_OFF (0)
#define WATCHDOG_16MS (_BV(WDE))
#define WATCHDOG_32MS (_BV(WDP0) | _BV(WDE))
#define WATCHDOG_64MS (_BV(WDP1) | _BV(WDE))
#define WATCHDOG_125MS (_BV(WDP1) | _BV(WDP0) | _BV(WDE))
#define WATCHDOG_250MS (_BV(WDP2) | _BV(WDE))
#define WATCHDOG_500MS (_BV(WDP2) | _BV(WDP0) | _BV(WDE))
#define WATCHDOG_1S (_BV(WDP2) | _BV(WDP1) | _BV(WDE))
#define WATCHDOG_2S (_BV(WDP2) | _BV(WDP1) | _BV(WDP0) | _BV(WDE))
#ifndef __AVR_ATmega8__
#define WATCHDOG_4S (_BV(WDP3) | _BV(WDE))
#define WATCHDOG_8S (_BV(WDP3) | _BV(WDP0) | _BV(WDE))
#endif

/* Function Prototypes */
/* The main function is in init9, which removes the interrupt vector table */
/* we don't need. It is also 'naked', which means the compiler does not */
/* generate any entry or exit code itself. */
int main(void) __attribute__ ((naked)) __attribute__ ((section (".init9")));
void putch(char);
uint8_t getch(void);
static inline void getNch(uint8_t); /* "static inline" is a compiler hint to reduce code size */
void verifySpace();
static inline void flash_led(uint8_t);
uint8_t getLen();
static inline void watchdogReset();
void watchdogConfig(uint8_t x);
#ifdef SOFT_UART
void uartDelay() __attribute__ ((naked));
#endif
void appStart() __attribute__ ((naked));

#if defined(__AVR_ATmega168__)
#define RAMSTART (0x100)
#define NRWWSTART (0x3800)
#elif defined(__AVR_ATmega328P__)
#define RAMSTART (0x100)
#define NRWWSTART (0x7000)
#elif defined (__AVR_ATmega644P__)
#define RAMSTART (0x100)
#define NRWWSTART (0xE000)
#elif defined(__AVR_ATtiny84__)
#define RAMSTART (0x100)
#define NRWWSTART (0x0000)
#elif defined(__AVR_ATmega1280__)
#define RAMSTART (0x200)
#define NRWWSTART (0xE000)
#elif defined(__AVR_ATmega8__) || defined(__AVR_ATmega88__)
#define RAMSTART (0x100)
#define NRWWSTART (0x1800)
#endif

/* C zero initialises all global variables. However, that requires */
/* These definitions are NOT zero initialised, but that doesn't matter */
/* This allows us to drop the zero init code, saving us memory */
#define buff ((uint8_t*)(RAMSTART))
#ifdef VIRTUAL_BOOT_PARTITION
#define rstVect (*(uint16_t*)(RAMSTART+SPM_PAGESIZE*2+4))
#define wdtVect (*(uint16_t*)(RAMSTART+SPM_PAGESIZE*2+6))
#endif

/* main program starts here */
int main(void) {
  uint8_t ch;

  /*
* Making these local and in registers prevents the need for initializing
* them, and also saves space because code no longer stores to memory.
* (initializing address keeps the compiler happy, but isn't really
* necessary, and uses 4 bytes of flash.)
*/
  register uint16_t address = 0;
  register uint8_t length;

  // After the zero init loop, this is the first code to run.
  //
  // This code makes the following assumptions:
  // No interrupts will execute
  // SP points to RAMEND
  // r1 contains zero
  //
  // If not, uncomment the following instructions:
  // cli();
  asm volatile ("clr __zero_reg__");
#ifdef __AVR_ATmega8__
  SP=RAMEND; // This is done by hardware reset
#endif

  // Adaboot no-wait mod
  ch = MCUSR;
  MCUSR = 0;
  if (!(ch & _BV(EXTRF))) appStart();

#if LED_START_FLASHES > 0
  // Set up Timer 1 for timeout counter
  TCCR1B = _BV(CS12) | _BV(CS10); // div 1024
#endif
#ifndef SOFT_UART
#ifdef __AVR_ATmega8__
  UCSRA = _BV(U2X); //Double speed mode USART
  UCSRB = _BV(RXEN) | _BV(TXEN); // enable Rx & Tx
  UCSRC = _BV(URSEL) | _BV(UCSZ1) | _BV(UCSZ0); // config USART; 8N1
  UBRRL = (uint8_t)( (F_CPU + BAUD_RATE * 4L) / (BAUD_RATE * 8L) - 1 );
#else
  UCSR0A = _BV(U2X0); //Double speed mode USART0
  UCSR0B = _BV(RXEN0) | _BV(TXEN0);
  UCSR0C = _BV(UCSZ00) | _BV(UCSZ01);
  UBRR0L = (uint8_t)( (F_CPU + BAUD_RATE * 4L) / (BAUD_RATE * 8L) - 1 );
#endif
#endif

  // Set up watchdog to trigger after 500ms
  watchdogConfig(WATCHDOG_1S);

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

#ifdef SOFT_UART
  /* Set TX pin as output */
  UART_DDR |= _BV(UART_TX_BIT);
#endif

#if LED_START_FLASHES > 0
  /* Flash onboard LED to signal entering of bootloader */
  flash_led(LED_START_FLASHES * 2);
#endif

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

    if(ch == STK_GET_PARAMETER) {
      unsigned char which = getch();
      verifySpace();
      if (which == 0x82) {
/*
* Send optiboot version as "minor SW version"
*/
putch(OPTIBOOT_MINVER);
      } else if (which == 0x81) {
putch(OPTIBOOT_MAJVER);
      } else {
/*
* GET PARAMETER returns a generic 0x03 reply for
* other parameters - enough to keep Avrdude happy
*/
putch(0x03);
      }
    }
    else if(ch == STK_SET_DEVICE) {
      // SET DEVICE is ignored
      getNch(20);
    }
    else if(ch == STK_SET_DEVICE_EXT) {
      // SET DEVICE EXT is ignored
      getNch(5);
    }
    else if(ch == STK_LOAD_ADDRESS) {
      // LOAD ADDRESS
      uint16_t newAddress;
      newAddress = getch();
      newAddress = (newAddress & 0xff) | (getch() << 8);
#ifdef RAMPZ
      // Transfer top bit to RAMPZ
      RAMPZ = (newAddress & 0x8000) ? 1 : 0;
#endif
      newAddress += newAddress; // Convert from word address to byte address
      address = newAddress;
      verifySpace();
    }
    else if(ch == STK_UNIVERSAL) {
      // UNIVERSAL command is ignored
      getNch(4);
      putch(0x00);
    }
    /* Write memory, length is big endian and is in bytes */
    else if(ch == STK_PROG_PAGE) {
      // PROGRAM PAGE - we support flash programming only, not EEPROM
      uint8_t *bufPtr;
      uint16_t addrPtr;

      getch(); /* getlen() */
      length = getch();
      getch();

      // If we are in RWW section, immediately start page erase
      if (address < NRWWSTART) __boot_page_erase_short((uint16_t)(void*)address);

      // While that is going on, read in page contents
      bufPtr = buff;
      do *bufPtr++ = getch();
      while (--length);

      // If we are in NRWW section, page erase has to be delayed until now.
      // Todo: Take RAMPZ into account
      if (address >= NRWWSTART) __boot_page_erase_short((uint16_t)(void*)address);

      // Read command terminator, start reply
      verifySpace();

      // If only a partial page is to be programmed, the erase might not be complete.
      // So check that here
      boot_spm_busy_wait();

#ifdef VIRTUAL_BOOT_PARTITION
      if ((uint16_t)(void*)address == 0) {
        // This is the reset vector page. We need to live-patch the code so the
        // bootloader runs.
        //
        // Move RESET vector to WDT vector
        uint16_t vect = buff[0] | (buff[1]<<8);
        rstVect = vect;
        wdtVect = buff[8] | (buff[9]<<8);
        vect -= 4; // Instruction is a relative jump (rjmp), so recalculate.
        buff[8] = vect & 0xff;
        buff[9] = vect >> 8;

        // Add jump to bootloader at RESET vector
        buff[0] = 0x7f;
        buff[1] = 0xce; // rjmp 0x1d00 instruction
      }
#endif

      // Copy buffer into programming buffer
      bufPtr = buff;
      addrPtr = (uint16_t)(void*)address;
      ch = SPM_PAGESIZE / 2;
      do {
        uint16_t a;
        a = *bufPtr++;
        a |= (*bufPtr++) << 8;
        __boot_page_fill_short((uint16_t)(void*)addrPtr,a);
        addrPtr += 2;
      } while (--ch);

      // Write from programming buffer
      __boot_page_write_short((uint16_t)(void*)address);
      boot_spm_busy_wait();

#if defined(RWWSRE)
      // Reenable read access to flash
      boot_rww_enable();
#endif

    }
    /* Read memory block mode, length is big endian. */
    else if(ch == STK_READ_PAGE) {
      // READ PAGE - we only read flash
      getch(); /* getlen() */
      length = getch();
      getch();

      verifySpace();
#ifdef VIRTUAL_BOOT_PARTITION
      do {
        // Undo vector patch in bottom page so verify passes
        if (address == 0) ch=rstVect & 0xff;
        else if (address == 1) ch=rstVect >> 8;
        else if (address == 8) ch=wdtVect & 0xff;
        else if (address == 9) ch=wdtVect >> 8;
        else ch = pgm_read_byte_near(address);
        address++;
        putch(ch);
      } while (--length);
#else
#ifdef __AVR_ATmega1280__
// do putch(pgm_read_byte_near(address++));
// while (--length);
      do {
        uint8_t result;
        __asm__ ("elpm %0,Z\n":"=r"(result):"z"(address));
        putch(result);
        address++;
      }
      while (--length);
#else
      do putch(pgm_read_byte_near(address++));
      while (--length);
#endif
#endif
    }

    /* Get device signature bytes */
    else if(ch == STK_READ_SIGN) {
      // READ SIGN - return what Avrdude wants to hear
      verifySpace();
      putch(SIGNATURE_0);
      putch(SIGNATURE_1);
      putch(SIGNATURE_2);
    }
    else if (ch == 'Q') {
      // Adaboot no-wait mod
      watchdogConfig(WATCHDOG_16MS);
      verifySpace();
    }
    else {
      // This covers the response to commands like STK_ENTER_PROGMODE
      verifySpace();
    }
    putch(STK_OK);
  }
}

void putch(char ch) {
#ifndef SOFT_UART
  while (!(UCSR0A & _BV(UDRE0)));
  UDR0 = ch;
#else
  __asm__ __volatile__ (
    " com %[ch]\n" // ones complement, carry set
    " sec\n"
    "1: brcc 2f\n"
    " cbi %[uartPort],%[uartBit]\n"
    " rjmp 3f\n"
    "2: sbi %[uartPort],%[uartBit]\n"
    " nop\n"
    "3: rcall uartDelay\n"
    " rcall uartDelay\n"
    " lsr %[ch]\n"
    " dec %[bitcnt]\n"
    " brne 1b\n"
    :
    :
      [bitcnt] "d" (10),
      [ch] "r" (ch),
      [uartPort] "I" (_SFR_IO_ADDR(UART_PORT)),
      [uartBit] "I" (UART_TX_BIT)
    :
      "r25"
  );
#endif
}

uint8_t getch(void) {
  uint8_t ch;

#ifdef LED_DATA_FLASH
#ifdef __AVR_ATmega8__
  LED_PORT ^= _BV(LED);
#else
  LED_PIN |= _BV(LED);
#endif
#endif

#ifdef SOFT_UART
  __asm__ __volatile__ (
    "1: sbic %[uartPin],%[uartBit]\n" // Wait for start edge
    " rjmp 1b\n"
    " rcall uartDelay\n" // Get to middle of start bit
    "2: rcall uartDelay\n" // Wait 1 bit period
    " rcall uartDelay\n" // Wait 1 bit period
    " clc\n"
    " sbic %[uartPin],%[uartBit]\n"
    " sec\n"
    " dec %[bitCnt]\n"
    " breq 3f\n"
    " ror %[ch]\n"
    " rjmp 2b\n"
    "3:\n"
    :
      [ch] "=r" (ch)
    :
      [bitCnt] "d" (9),
      [uartPin] "I" (_SFR_IO_ADDR(UART_PIN)),
      [uartBit] "I" (UART_RX_BIT)
    :
      "r25"
);
#else
  while(!(UCSR0A & _BV(RXC0)))
    ;
  if (!(UCSR0A & _BV(FE0))) {
      /*
* A Framing Error indicates (probably) that something is talking
* to us at the wrong bit rate. Assume that this is because it
* expects to be talking to the application, and DON'T reset the
* watchdog. This should cause the bootloader to abort and run
* the application "soon", if it keeps happening. (Note that we
* don't care that an invalid char is returned...)
*/
    watchdogReset();
  }
  
  ch = UDR0;
#endif

#ifdef LED_DATA_FLASH
#ifdef __AVR_ATmega8__
  LED_PORT ^= _BV(LED);
#else
  LED_PIN |= _BV(LED);
#endif
#endif

  return ch;
}

#ifdef SOFT_UART
// AVR350 equation: #define UART_B_VALUE (((F_CPU/BAUD_RATE)-23)/6)
// Adding 3 to numerator simulates nearest rounding for more accurate baud rates
#define UART_B_VALUE (((F_CPU/BAUD_RATE)-20)/6)
#if UART_B_VALUE > 255
#error Baud rate too slow for soft UART
#endif

void uartDelay() {
  __asm__ __volatile__ (
    "ldi r25,%[count]\n"
    "1:dec r25\n"
    "brne 1b\n"
    "ret\n"
    ::[count] "M" (UART_B_VALUE)
  );
}
#endif

void getNch(uint8_t count) {
  do getch(); while (--count);
  verifySpace();
}

void verifySpace() {
  if (getch() != CRC_EOP) {
    watchdogConfig(WATCHDOG_16MS); // shorten WD timeout
    while (1) // and busy-loop so that WD causes
      ; // a reset and app start.
  }
  putch(STK_INSYNC);
}

#if LED_START_FLASHES > 0
void flash_led(uint8_t count) {
  do {
    TCNT1 = -(F_CPU/(1024*16));
    TIFR1 = _BV(TOV1);
    while(!(TIFR1 & _BV(TOV1)));
#ifdef __AVR_ATmega8__
    LED_PORT ^= _BV(LED);
#else
    LED_PIN |= _BV(LED);
#endif
    watchdogReset();
  } while (--count);
}
#endif

// Watchdog functions. These are only safe with interrupts turned off.
void watchdogReset() {
  __asm__ __volatile__ (
    "wdr\n"
  );
}

void watchdogConfig(uint8_t x) {
  WDTCSR = _BV(WDCE) | _BV(WDE);
  WDTCSR = x;
}

void appStart() {
  watchdogConfig(WATCHDOG_OFF);
  __asm__ __volatile__ (
#ifdef VIRTUAL_BOOT_PARTITION
    // Jump to WDT vector
    "ldi r30,4\n"
    "clr r31\n"
#else
    // Jump to RST vector
    "clr r30\n"
    "clr r31\n"
#endif
    "ijmp\n"
  );
}
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