ARDUINO MEGA Update Bootloader

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Note: This document only applies to the MEGA 2560 and MEGA ADK Arduino Boards. All other Arduino boards bootloaders are good!

Arduino 2560 Bootloader Issue

The current bootloader burned onto the Arduino MEGA 2560/ADK is not compatible with ROBOTC. In its current form, you will be able to download the ROBOTC Firmware to the Arduino MEGA 2560/ADK, but you will not able to download any user programs.

The reason for this is because there is a bug in the Arduino MEGA 2560/ADK firmware that does not allow flash write commands to start at anywhere but the beginning of flash memory (0x000000). See the bottom of this page for more technical details.

Because ROBOTC is not able to burn a new bootloader as of today, you will need to use the Arduino's Open Source language with our a modified bootloader file to re-burn your bootloader on your Arduino MEGA 2560/ADK boards. Once the new bootloader is burned, you will be able to program your Arduino MEGA 2560/ADK with both ROBOTC and the Arduino Open Source language.

Hardware Needed

To burn a new version of the Arduino bootloader to your MEGA 2560/ADK, you'll need an AVR ISP Compatible downloader.

Using an AVR ISP (In System Programmer)

  • Your Arduino MEGA 2560/ADK (to program)
  • An AVR Programmer such as the Pocket Programmer
  • An AVR Programming Cable (the pocket programmer comes with one)

If you have extra Arduino boards, but no ISP programmer, SparkFun.com has a cool tutorial on how to flash a bootloader using an Arduino as an ISP.

Using another Arduino as an ISP

  • Your Arduino MEGA 2560/ADK (to program)
  • A Working Arduino (doesn't matter what kind)
  • Some Male-to-Male Jumper Cables

For instructions on this method, take a look at the SparkFun.com website: http://www.sparkfun.com/tutorials/247

Software Needed

ROBOTC is not currently able to burn a bootloader onto an Arduino board, so you'll need to download a copy of the latest version of the Arduino Open-Source programming language.

In addition, you'll need the ROBOTC modified bootloader. You can download that here:

link title

Bootload Download Instructions

CopyBootloader.png

  • Power up your Arduino MEGA 2560/ADK (either via USB or external power)
  • Plug in your AVR ISP Programmer to your computer (make sure you have any required drivers installed)
  • Connect your AVR ISP Programmer into your Arduino MEGA 2560/ADK Board via the ISP Header (the 2x3 header pins right above the Arduino Logo)
  • Launch the Arduino Open Source Software

ArduinoLaunch.png

  • Change your settings in the Arduino Software to look for an Arduino MEGA 2560/ADK

ArduinoSelectPlatform.png

  • Change your settings in the Arduino Software to select your ISP Programmer Type (Check your programmer's documentation for the exact model)

ArduinoSelectProgrammer.png

  • Select the "Burn Bootloader" option under the "Tools" menu. The modified bootloader will now be sent to your Arduino. This typically take a minute or so.

BurnBootloader.png

  • You should be all set to download ROBOTC firmware and start using your Arduino MEGA 2560/ADK with ROBOTC!

Technical Details

The Arduino Bootloader sets the "eraseAddress" to zero every time the bootloader is called. ROBOTC called the "Load Address" command to set the address in which we want to write/verify when downloading program.

When writing a page of memory to the arduino, the Arduino bootloader will erase the existing page and write a whole new page.

In the scenario of downloading firmware, everything is great because the Erase Address and the Loaded Address both start at zero.

In the scenario of writing a user program, we start writing at memory location 0x7000, but the Bootloader erases information starting at location zero because the "Load Address" command doesn't update where to erase.

Our modification is to set both the Load Address and the Erase Address so the activity of writing a user program doesn't cause the firmware to be accidentally erased!

Original Bootloader

case CMD_LOAD_ADDRESS:
 #if defined(RAMPZ)
  address = (((address_t)(msgBuffer[1])<<24)|((address_t)(msgBuffer[2])<<16)|
            ((address_t)(msgBuffer[3])<<8)|msgBuffer[4]))<<1;
 #else
  address = (((msgBuffer[3])<<8)|(msgBuffer[4]))<<1;  //convert word to byte address
 #endif
 msgLength = 2;
 msgBuffer[1] =	STATUS_CMD_OK;
 break;
 
case CMD_PROGRAM_FLASH_ISP:
case CMD_PROGRAM_EEPROM_ISP:
{
  unsigned int	size	=	((msgBuffer[1])<<8) | msgBuffer[2];
  unsigned char	*p	=	msgBuffer+10;
  unsigned int	data;
  unsigned char	highByte, lowByte;
  address_t tempaddress	= address;
 
  if ( msgBuffer[0] == CMD_PROGRAM_FLASH_ISP )
  {
    // erase only main section (bootloader protection)
    if (eraseAddress < APP_END )
    {
      boot_page_erase(eraseAddress);	// Perform page erase
      boot_spm_busy_wait();		// Wait until the memory is erased.
      eraseAddress += SPM_PAGESIZE;	// point to next page to be erase
    }

ROBOTC Compatible Modification

case CMD_PROGRAM_FLASH_ISP:
case CMD_PROGRAM_EEPROM_ISP:
{
  unsigned int	size	=	((msgBuffer[1])<<8) | msgBuffer[2];
  unsigned char	*p	=	msgBuffer+10;
  unsigned int	data;
  unsigned char	highByte, lowByte;
  address_t		tempaddress	=	address;
 
 
  if ( msgBuffer[0] == CMD_PROGRAM_FLASH_ISP )
  {
    eraseAddress = address & 0xFFFFFF00;   // ROBOTC Custom Bootloader Addition
 
    // erase only main section (bootloader protection)
    if (eraseAddress < APP_END )
    {
      boot_page_erase(eraseAddress);	// Perform page erase
      boot_spm_busy_wait();		// Wait until the memory is erased.
      eraseAddress += SPM_PAGESIZE;	// point to next page to be erase
    }