Master the Art of Bootloader Burning with Arduino as ISP: A Comprehensive Guide

/*
  Made on 18 may 2021
  Home
  based on Arduino Library
*/
// ArduinoISP
// Copyright (c) 2008-2011 Randall Bohn
// If you require a license, see
// http://www.opensource.org/licenses/bsd-license.php
//
// This sketch turns the Arduino into a AVRISP using the following Arduino pins:
//
// Pin 10 is used to reset the target microcontroller.
//
// By default, the hardware SPI pins MISO, MOSI and SCK are used to communicate
// with the target. On all Arduinos, these pins can be found
// on the ICSP/SPI header:
//
//               MISO °. . 5V (!) Avoid this pin on Due, Zero...
//               SCK   . . MOSI
//                     . . GND
//
// On some Arduinos (Uno,...), pins MOSI, MISO and SCK are the same pins as
// digital pin 11, 12 and 13, respectively. That is why many tutorials instruct
// you to hook up the target to these pins. If you find this wiring more
// practical, have a define USE_OLD_STYLE_WIRING. This will work even when not
// using an Uno. (On an Uno this is not needed).
//
// Alternatively you can use any other digital pin by configuring
// software ('BitBanged') SPI and having appropriate defines for PIN_MOSI,
// PIN_MISO and PIN_SCK.
//
// IMPORTANT: When using an Arduino that is not 5V tolerant (Due, Zero, ...) as
// the programmer, make sure to not expose any of the programmer's pins to 5V.
// A simple way to accomplish this is to power the complete system (programmer
// and target) at 3V3.
//
// Put an LED (with resistor) on the following pins:
// 9: Heartbeat   - shows the programmer is running
// 8: Error       - Lights up if something goes wrong (use red if that makes sense)
// 7: Programming - In communication with the slave
//

#include "Arduino.h"
#undef SERIAL


#define PROG_FLICKER true

// Configure SPI clock (in Hz).
// E.g. for an ATtiny @ 128 kHz: the datasheet states that both the high and low
// SPI clock pulse must be > 2 CPU cycles, so take 3 cycles i.e. divide target
// f_cpu by 6:
//     #define SPI_CLOCK            (128000/6)
//
// A clock slow enough for an ATtiny85 @ 1 MHz, is a reasonable default:

#define SPI_CLOCK 		(1000000/6)


// Select hardware or software SPI, depending on SPI clock.
// Currently only for AVR, for other architectures (Due, Zero,...), hardware SPI
// is probably too fast anyway.

#if defined(ARDUINO_ARCH_AVR)

#if SPI_CLOCK > (F_CPU / 128)
#define USE_HARDWARE_SPI
#endif

#endif

// Configure which pins to use:

// The standard pin configuration.
#ifndef ARDUINO_HOODLOADER2

#define RESET     10 // Use pin 10 to reset the target rather than SS
#define LED_HB    9
#define LED_ERR   8
#define LED_PMODE 7

// Uncomment following line to use the old Uno style wiring
// (using pin 11, 12 and 13 instead of the SPI header) on Leonardo, Due...

// #define USE_OLD_STYLE_WIRING

#ifdef USE_OLD_STYLE_WIRING

#define PIN_MOSI	11
#define PIN_MISO	12
#define PIN_SCK		13

#endif

// HOODLOADER2 means running sketches on the ATmega16U2 serial converter chips
// on Uno or Mega boards. We must use pins that are broken out:
#else

#define RESET     	4
#define LED_HB    	7
#define LED_ERR   	6
#define LED_PMODE 	5

#endif

// By default, use hardware SPI pins:
#ifndef PIN_MOSI
#define PIN_MOSI 	MOSI
#endif

#ifndef PIN_MISO
#define PIN_MISO 	MISO
#endif

#ifndef PIN_SCK
#define PIN_SCK 	SCK
#endif

// Force bitbanged SPI if not using the hardware SPI pins:
#if (PIN_MISO != MISO) ||  (PIN_MOSI != MOSI) || (PIN_SCK != SCK)
#undef USE_HARDWARE_SPI
#endif


// Configure the serial port to use.
//
// Prefer the USB virtual serial port (aka. native USB port), if the Arduino has one:
//   - it does not autoreset (except for the magic baud rate of 1200).
//   - it is more reliable because of USB handshaking.
//
// Leonardo and similar have an USB virtual serial port: 'Serial'.
// Due and Zero have an USB virtual serial port: 'SerialUSB'.
//
// On the Due and Zero, 'Serial' can be used too, provided you disable autoreset.
// To use 'Serial': #define SERIAL Serial

#ifdef SERIAL_PORT_USBVIRTUAL
#define SERIAL SERIAL_PORT_USBVIRTUAL
#else
#define SERIAL Serial
#endif


// Configure the baud rate:

#define BAUDRATE	19200
// #define BAUDRATE	115200
// #define BAUDRATE	1000000


#define HWVER 2
#define SWMAJ 1
#define SWMIN 18

// STK Definitions
#define STK_OK      0x10
#define STK_FAILED  0x11
#define STK_UNKNOWN 0x12
#define STK_INSYNC  0x14
#define STK_NOSYNC  0x15
#define CRC_EOP     0x20 //ok it is a space...

void pulse(int pin, int times);

#ifdef USE_HARDWARE_SPI
#include "SPI.h"
#else

#define SPI_MODE0 0x00

class SPISettings {
  public:
    // clock is in Hz
    SPISettings(uint32_t clock, uint8_t bitOrder, uint8_t dataMode) : clock(clock) {
      (void) bitOrder;
      (void) dataMode;
    };

  private:
    uint32_t clock;

    friend class BitBangedSPI;
};

class BitBangedSPI {
  public:
    void begin() {
      digitalWrite(PIN_SCK, LOW);
      digitalWrite(PIN_MOSI, LOW);
      pinMode(PIN_SCK, OUTPUT);
      pinMode(PIN_MOSI, OUTPUT);
      pinMode(PIN_MISO, INPUT);
    }

    void beginTransaction(SPISettings settings) {
      pulseWidth = (500000 + settings.clock - 1) / settings.clock;
      if (pulseWidth == 0)
        pulseWidth = 1;
    }

    void end() {}

    uint8_t transfer (uint8_t b) {
      for (unsigned int i = 0; i < 8; ++i) {
        digitalWrite(PIN_MOSI, (b & 0x80) ? HIGH : LOW);
        digitalWrite(PIN_SCK, HIGH);
        delayMicroseconds(pulseWidth);
        b = (b << 1) | digitalRead(PIN_MISO);
        digitalWrite(PIN_SCK, LOW); // slow pulse
        delayMicroseconds(pulseWidth);
      }
      return b;
    }

  private:
    unsigned long pulseWidth; // in microseconds
};

static BitBangedSPI SPI;

#endif

void setup() {
  SERIAL.begin(BAUDRATE);

  pinMode(LED_PMODE, OUTPUT);
  pulse(LED_PMODE, 2);
  pinMode(LED_ERR, OUTPUT);
  pulse(LED_ERR, 2);
  pinMode(LED_HB, OUTPUT);
  pulse(LED_HB, 2);

}

int error = 0;
int pmode = 0;
// address for reading and writing, set by 'U' command
unsigned int here;
uint8_t buff[256]; // global block storage

#define beget16(addr) (*addr * 256 + *(addr+1) )
typedef struct param {
  uint8_t devicecode;
  uint8_t revision;
  uint8_t progtype;
  uint8_t parmode;
  uint8_t polling;
  uint8_t selftimed;
  uint8_t lockbytes;
  uint8_t fusebytes;
  uint8_t flashpoll;
  uint16_t eeprompoll;
  uint16_t pagesize;
  uint16_t eepromsize;
  uint32_t flashsize;
}
parameter;

parameter param;

// this provides a heartbeat on pin 9, so you can tell the software is running.
uint8_t hbval = 128;
int8_t hbdelta = 8;
void heartbeat() {
  static unsigned long last_time = 0;
  unsigned long now = millis();
  if ((now - last_time) < 40)
    return;
  last_time = now;
  if (hbval > 192) hbdelta = -hbdelta;
  if (hbval < 32) hbdelta = -hbdelta;
  hbval += hbdelta;
  analogWrite(LED_HB, hbval);
}

static bool rst_active_high;

void reset_target(bool reset) {
  digitalWrite(RESET, ((reset && rst_active_high) || (!reset && !rst_active_high)) ? HIGH : LOW);
}

void loop(void) {
  // is pmode active?
  if (pmode) {
    digitalWrite(LED_PMODE, HIGH);
  } else {
    digitalWrite(LED_PMODE, LOW);
  }
  // is there an error?
  if (error) {
    digitalWrite(LED_ERR, HIGH);
  } else {
    digitalWrite(LED_ERR, LOW);
  }

  // light the heartbeat LED
  heartbeat();
  if (SERIAL.available()) {
    avrisp();
  }
}

uint8_t getch() {
  while (!SERIAL.available());
  return SERIAL.read();
}
void fill(int n) {
  for (int x = 0; x < n; x++) {
    buff[x] = getch();
  }
}

#define PTIME 30
void pulse(int pin, int times) {
  do {
    digitalWrite(pin, HIGH);
    delay(PTIME);
    digitalWrite(pin, LOW);
    delay(PTIME);
  } while (times--);
}

void prog_lamp(int state) {
  if (PROG_FLICKER) {
    digitalWrite(LED_PMODE, state);
  }
}

uint8_t spi_transaction(uint8_t a, uint8_t b, uint8_t c, uint8_t d) {
  SPI.transfer(a);
  SPI.transfer(b);
  SPI.transfer(c);
  return SPI.transfer(d);
}

void empty_reply() {
  if (CRC_EOP == getch()) {
    SERIAL.print((char)STK_INSYNC);
    SERIAL.print((char)STK_OK);
  } else {
    error++;
    SERIAL.print((char)STK_NOSYNC);
  }
}

void breply(uint8_t b) {
  if (CRC_EOP == getch()) {
    SERIAL.print((char)STK_INSYNC);
    SERIAL.print((char)b);
    SERIAL.print((char)STK_OK);
  } else {
    error++;
    SERIAL.print((char)STK_NOSYNC);
  }
}

void get_version(uint8_t c) {
  switch (c) {
    case 0x80:
      breply(HWVER);
      break;
    case 0x81:
      breply(SWMAJ);
      break;
    case 0x82:
      breply(SWMIN);
      break;
    case 0x93:
      breply('S'); // serial programmer
      break;
    default:
      breply(0);
  }
}

void set_parameters() {
  // call this after reading parameter packet into buff[]
  param.devicecode = buff[0];
  param.revision   = buff[1];
  param.progtype   = buff[2];
  param.parmode    = buff[3];
  param.polling    = buff[4];
  param.selftimed  = buff[5];
  param.lockbytes  = buff[6];
  param.fusebytes  = buff[7];
  param.flashpoll  = buff[8];
  // ignore buff[9] (= buff[8])
  // following are 16 bits (big endian)
  param.eeprompoll = beget16(&buff[10]);
  param.pagesize   = beget16(&buff[12]);
  param.eepromsize = beget16(&buff[14]);

  // 32 bits flashsize (big endian)
  param.flashsize = buff[16] * 0x01000000
                    + buff[17] * 0x00010000
                    + buff[18] * 0x00000100
                    + buff[19];

  // AVR devices have active low reset, AT89Sx are active high
  rst_active_high = (param.devicecode >= 0xe0);
}

void start_pmode() {

  // Reset target before driving PIN_SCK or PIN_MOSI

  // SPI.begin() will configure SS as output, so SPI master mode is selected.
  // We have defined RESET as pin 10, which for many Arduinos is not the SS pin.
  // So we have to configure RESET as output here,
  // (reset_target() first sets the correct level)
  reset_target(true);
  pinMode(RESET, OUTPUT);
  SPI.begin();
  SPI.beginTransaction(SPISettings(SPI_CLOCK, MSBFIRST, SPI_MODE0));

  // See AVR datasheets, chapter "SERIAL_PRG Programming Algorithm":

  // Pulse RESET after PIN_SCK is low:
  digitalWrite(PIN_SCK, LOW);
  delay(20); // discharge PIN_SCK, value arbitrarily chosen
  reset_target(false);
  // Pulse must be minimum 2 target CPU clock cycles so 100 usec is ok for CPU
  // speeds above 20 KHz
  delayMicroseconds(100);
  reset_target(true);

  // Send the enable programming command:
  delay(50); // datasheet: must be > 20 msec
  spi_transaction(0xAC, 0x53, 0x00, 0x00);
  pmode = 1;
}

void end_pmode() {
  SPI.end();
  // We're about to take the target out of reset so configure SPI pins as input
  pinMode(PIN_MOSI, INPUT);
  pinMode(PIN_SCK, INPUT);
  reset_target(false);
  pinMode(RESET, INPUT);
  pmode = 0;
}

void universal() {
  uint8_t ch;

  fill(4);
  ch = spi_transaction(buff[0], buff[1], buff[2], buff[3]);
  breply(ch);
}

void flash(uint8_t hilo, unsigned int addr, uint8_t data) {
  spi_transaction(0x40 + 8 * hilo,
                  addr >> 8 & 0xFF,
                  addr & 0xFF,
                  data);
}
void commit(unsigned int addr) {
  if (PROG_FLICKER) {
    prog_lamp(LOW);
  }
  spi_transaction(0x4C, (addr >> 8) & 0xFF, addr & 0xFF, 0);
  if (PROG_FLICKER) {
    delay(PTIME);
    prog_lamp(HIGH);
  }
}

unsigned int current_page() {
  if (param.pagesize == 32) {
    return here & 0xFFFFFFF0;
  }
  if (param.pagesize == 64) {
    return here & 0xFFFFFFE0;
  }
  if (param.pagesize == 128) {
    return here & 0xFFFFFFC0;
  }
  if (param.pagesize == 256) {
    return here & 0xFFFFFF80;
  }
  return here;
}


void write_flash(int length) {
  fill(length);
  if (CRC_EOP == getch()) {
    SERIAL.print((char) STK_INSYNC);
    SERIAL.print((char) write_flash_pages(length));
  } else {
    error++;
    SERIAL.print((char) STK_NOSYNC);
  }
}

uint8_t write_flash_pages(int length) {
  int x = 0;
  unsigned int page = current_page();
  while (x < length) {
    if (page != current_page()) {
      commit(page);
      page = current_page();
    }
    flash(LOW, here, buff[x++]);
    flash(HIGH, here, buff[x++]);
    here++;
  }

  commit(page);

  return STK_OK;
}

#define EECHUNK (32)
uint8_t write_eeprom(unsigned int length) {
  // here is a word address, get the byte address
  unsigned int start = here * 2;
  unsigned int remaining = length;
  if (length > param.eepromsize) {
    error++;
    return STK_FAILED;
  }
  while (remaining > EECHUNK) {
    write_eeprom_chunk(start, EECHUNK);
    start += EECHUNK;
    remaining -= EECHUNK;
  }
  write_eeprom_chunk(start, remaining);
  return STK_OK;
}
// write (length) bytes, (start) is a byte address
uint8_t write_eeprom_chunk(unsigned int start, unsigned int length) {
  // this writes byte-by-byte, page writing may be faster (4 bytes at a time)
  fill(length);
  prog_lamp(LOW);
  for (unsigned int x = 0; x < length; x++) {
    unsigned int addr = start + x;
    spi_transaction(0xC0, (addr >> 8) & 0xFF, addr & 0xFF, buff[x]);
    delay(45);
  }
  prog_lamp(HIGH);
  return STK_OK;
}

void program_page() {
  char result = (char) STK_FAILED;
  unsigned int length = 256 * getch();
  length += getch();
  char memtype = getch();
  // flash memory @here, (length) bytes
  if (memtype == 'F') {
    write_flash(length);
    return;
  }
  if (memtype == 'E') {
    result = (char)write_eeprom(length);
    if (CRC_EOP == getch()) {
      SERIAL.print((char) STK_INSYNC);
      SERIAL.print(result);
    } else {
      error++;
      SERIAL.print((char) STK_NOSYNC);
    }
    return;
  }
  SERIAL.print((char)STK_FAILED);
  return;
}

uint8_t flash_read(uint8_t hilo, unsigned int addr) {
  return spi_transaction(0x20 + hilo * 8,
                         (addr >> 8) & 0xFF,
                         addr & 0xFF,
                         0);
}

char flash_read_page(int length) {
  for (int x = 0; x < length; x += 2) {
    uint8_t low = flash_read(LOW, here);
    SERIAL.print((char) low);
    uint8_t high = flash_read(HIGH, here);
    SERIAL.print((char) high);
    here++;
  }
  return STK_OK;
}

char eeprom_read_page(int length) {
  // here again we have a word address
  int start = here * 2;
  for (int x = 0; x < length; x++) {
    int addr = start + x;
    uint8_t ee = spi_transaction(0xA0, (addr >> 8) & 0xFF, addr & 0xFF, 0xFF);
    SERIAL.print((char) ee);
  }
  return STK_OK;
}

void read_page() {
  char result = (char)STK_FAILED;
  int length = 256 * getch();
  length += getch();
  char memtype = getch();
  if (CRC_EOP != getch()) {
    error++;
    SERIAL.print((char) STK_NOSYNC);
    return;
  }
  SERIAL.print((char) STK_INSYNC);
  if (memtype == 'F') result = flash_read_page(length);
  if (memtype == 'E') result = eeprom_read_page(length);
  SERIAL.print(result);
}

void read_signature() {
  if (CRC_EOP != getch()) {
    error++;
    SERIAL.print((char) STK_NOSYNC);
    return;
  }
  SERIAL.print((char) STK_INSYNC);
  uint8_t high = spi_transaction(0x30, 0x00, 0x00, 0x00);
  SERIAL.print((char) high);
  uint8_t middle = spi_transaction(0x30, 0x00, 0x01, 0x00);
  SERIAL.print((char) middle);
  uint8_t low = spi_transaction(0x30, 0x00, 0x02, 0x00);
  SERIAL.print((char) low);
  SERIAL.print((char) STK_OK);
}
//////////////////////////////////////////
//////////////////////////////////////////


////////////////////////////////////
////////////////////////////////////
void avrisp() {
  uint8_t ch = getch();
  switch (ch) {
    case '0': // signon
      error = 0;
      empty_reply();
      break;
    case '1':
      if (getch() == CRC_EOP) {
        SERIAL.print((char) STK_INSYNC);
        SERIAL.print("AVR ISP");
        SERIAL.print((char) STK_OK);
      }
      else {
        error++;
        SERIAL.print((char) STK_NOSYNC);
      }
      break;
    case 'A':
      get_version(getch());
      break;
    case 'B':
      fill(20);
      set_parameters();
      empty_reply();
      break;
    case 'E': // extended parameters - ignore for now
      fill(5);
      empty_reply();
      break;
    case 'P':
      if (!pmode)
        start_pmode();
      empty_reply();
      break;
    case 'U': // set address (word)
      here = getch();
      here += 256 * getch();
      empty_reply();
      break;

    case 0x60: //STK_PROG_FLASH
      getch(); // low addr
      getch(); // high addr
      empty_reply();
      break;
    case 0x61: //STK_PROG_DATA
      getch(); // data
      empty_reply();
      break;

    case 0x64: //STK_PROG_PAGE
      program_page();
      break;

    case 0x74: //STK_READ_PAGE 't'
      read_page();
      break;

    case 'V': //0x56
      universal();
      break;
    case 'Q': //0x51
      error = 0;
      end_pmode();
      empty_reply();
      break;

    case 0x75: //STK_READ_SIGN 'u'
      read_signature();
      break;

    // expecting a command, not CRC_EOP
    // this is how we can get back in sync
    case CRC_EOP:
      error++;
      SERIAL.print((char) STK_NOSYNC);
      break;

    // anything else we will return STK_UNKNOWN
    default:
      error++;
      if (CRC_EOP == getch())
        SERIAL.print((char)STK_UNKNOWN);
      else
        SERIAL.print((char)STK_NOSYNC);
  }
}