Arduino Mega 2560 with Optiboot Flash

Write permanent data in flash memory at run-time on Arduino Mega 2560.

To write permanent data in flash memory at run-time on Arduino Mega 2560, we need to burn a particular bootloader: Optiboot Flash.

What is Optiboot Flash ?

Optiboot is an easy to install upgrade to the Arduino bootloader within Arduino boards. It provides the following features:

• Allows larger sketches. Optiboot is only 512 bytes, freeing 1.5k of extra code space compared to older bootloaders.
• Makes your sketches upload faster. Optiboot operates at higher baud rates and has streamlined programming.
• Adaboot performance improvements. Optiboot implements "fastboot" that starts sketches immediate after power-on.
• Compatible with ATmega8, ATmega168, and ATmega328p Arduinos and derivatives including Lilypad, Pro, Nano, and many derivatives.
• Works with MANY additional Atmel AVR chips - almost anything that supports bootloads or "flash self-programming." This includes chips from ATtiny 8pin chips through the 100pin ATmega2560 used on Arduino Mega.
• Supports alternate serial ports, CPU frequencies and baud rates.

There are some major repositories of "generic" versions of cores for various targets, including:

• MegaCore by MCUdude which supports large AVRs like ATmega128, ATmega640, ATmega1280, ATmega1281, ATmega2560 and ATmega2561.

Optiboot Flash is part of MegaCore and provides key features:

• Small in size (<512B when EEPROM upload support is disabled)
• Supports baudrates upto 1Mbit
• Supports write to flash within application
• Compatible with a most AVR microcontrollers
• EEPROM upload support

Easy process to burn bootloader

We burn the optiboot_flash bootloader with an easy process using:

• Arduino IDE
• USB AVR programmer which emulates an STK500 on a virtual serial port
• MegaCore, an Arduino core for ATmega64, ATmega128, ATmega640, ATmega1280, ATmega1281, ATmega2560, ATmega2561, AT90CAN32, AT90CAN64 and AT90CAN128, all running Optiboot flash.

Required hardware and software

• Arduino Mega 2560 Rev3 or Elegoo Mega 2560 R3

• 9v adapter for Arduino

• Pololu USB AVR Programmer v2.1 or equivalent

• Pololu USB AVR Programmer v2 Software and Drivers for Windows (.msi)

• Arduino IDE for Windows (release 1.8.13 at this time)

• MegaCore: an Arduino core for ATmega2560 running Optiboot flash

In ./extras folder you will find software that we used the time I wrote this how-to:

• Pololu USB AVR Programmer Drivers 2.1.1.0 for Windows
• MegaCore source code in MegaCore-master.zip (get the latest)

Connect Mega and AVR programmer with ISP cable

First, install AVR programmer drivers: Pololu USB AVR Programmer v2 Software and Drivers for Windows

The correct connection:

Test the AVR programmer

1. Connect you PC to the AVR programmer with an USB cable and power the Mega 2560 with a 9v adapter:

2. Open Arduino IDE and load Examples/01.Basics/Blink sketch

3. Upload sketch to Mega via AVR programmer:

   • Select Tools/Programmer: "Atmel STK500 development board"
   • Upload with Sketch/Upload Using Programmer ctrl-Shift-U

4. Check that the Mega on-board LED is blinking: we are ready to continue

Install MegaCore boards manager

We follow instructions given by MCUdude in there.

• Open the Arduino IDE.

• Open the File > Preferences menu item.

• Enter the following URL in Additional Boards Manager URLs: https://mcudude.github.io/MegaCore/package_MCUdude_MegaCore_index.json

• Open the Tools > Board > Boards Manager... menu item.

• Wait for the platform indexes to finish downloading.

• Scroll down until you see the MegaCore entry and click on it.

  

• Click Install.

• After installation is complete close the Boards Manager window.

Burn optiboot_flash

We follow instructions given by MCUdude in there.

1. Install the files as directed, usually (for Arduino 1.0+) in a subdirectory of your personal sketch's ../hardware/ directory:

   • Download MegaCore source code: MegaCore-master.zip from https://github.com/MCUdude/MegaCore

   • Extract the optiboot_flash folder from MegaCore-master.zip in: C:\Program Files (x86)\Arduino\hardware\arduino\avr\bootloaders

     

2. Connect a device programmer to the ISP connector of the target board, we've done that when we tested the AVR programmer:

   

3. Running the Arduino IDE, select the Tools/Board of the target chip, and the Tools/Programmer of your programmer (Atmel STK500 development board), and if necessary the Tools/Serial port of the programmer:

   • we need to select the ATmega2560 as a Megacore board

   • ATmega2560 board default settings works well

     

4. Proceed : select Tools/Burn Bootloader

   avrdude: Version 6.3-20190619
            Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
            Copyright (c) 2007-2014 Joerg Wunsch
   
            System wide configuration file is "C:\Users\jm_de\AppData\Local\Arduino15\packages\MegaCore\hardware\avr\2.0.3/avrdude.conf"
   
            Using Port                    : COM5
            Using Programmer              : stk500
            AVR Part                      : ATmega2560
            Chip Erase delay              : 9000 us
            PAGEL                         : PD7
            BS2                           : PA0
            RESET disposition             : dedicated
            RETRY pulse                   : SCK
            serial program mode           : yes
            parallel program mode         : yes
            Timeout                       : 200
            StabDelay                     : 100
            CmdexeDelay                   : 25
            SyncLoops                     : 32
            ByteDelay                     : 0
            PollIndex                     : 3
            PollValue                     : 0x53
            Memory Detail                 :
   
                                     Block Poll               Page                       Polled
              Memory Type Mode Delay Size  Indx Paged  Size   Size #Pages MinW  MaxW   ReadBack
              ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
              eeprom        65    10     8    0 no       4096    8      0  9000  9000 0x00 0x00
              flash         65    10   256    0 yes    262144  256   1024  4500  4500 0x00 0x00
              lfuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
              hfuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
              efuse          0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
              lock           0     0     0    0 no          1    0      0  9000  9000 0x00 0x00
              calibration    0     0     0    0 no          1    0      0     0     0 0x00 0x00
              signature      0     0     0    0 no          3    0      0     0     0 0x00 0x00
   
            Programmer Type : STK500V2
            Description     : Atmel STK500
            Programmer Model: STK500
            Hardware Version: 15
            Firmware Version Master : 2.10
            Topcard         : Unknown
            Vtarget         : 5.1 V
            SCK period      : 8.7 us
            Varef           : 0.0 V
            Oscillator      : Off
   
   avrdude: AVR device initialized and ready to accept instructions
   
   Reading | ################################################## | 100% 0.00s
   
   avrdude: Device signature = 0x1e9801 (probably m2560)
   avrdude: erasing chip
   avrdude: reading input file "0x3f"
   avrdude: writing lock (1 bytes):
   
   Writing | ################################################## | 100% 0.00s
   
   avrdude: 1 bytes of lock written
   avrdude: verifying lock memory against 0x3f:
   avrdude: load data lock data from input file 0x3f:
   avrdude: input file 0x3f contains 1 bytes
   avrdude: reading on-chip lock data:
   
   Reading | ################################################## | 100% 0.00s
   
   avrdude: verifying ...
   avrdude: 1 bytes of lock verified
   avrdude: reading input file "0xfd"
   avrdude: writing efuse (1 bytes):
   
   Writing | ################################################## | 100% 0.00s
   
   avrdude: 1 bytes of efuse written
   avrdude: verifying efuse memory against 0xfd:
   avrdude: load data efuse data from input file 0xfd:
   avrdude: input file 0xfd contains 1 bytes
   avrdude: reading on-chip efuse data:
   
   Reading | ################################################## | 100% 0.00s
   
   avrdude: verifying ...
   avrdude: 1 bytes of efuse verified
   avrdude: reading input file "0xd6"
   avrdude: writing hfuse (1 bytes):
   
   Writing | ################################################## | 100% 0.01s
   
   avrdude: 1 bytes of hfuse written
   avrdude: verifying hfuse memory against 0xd6:
   avrdude: load data hfuse data from input file 0xd6:
   avrdude: input file 0xd6 contains 1 bytes
   avrdude: reading on-chip hfuse data:
   
   Reading | ################################################## | 100% 0.00s
   
   avrdude: verifying ...
   avrdude: 1 bytes of hfuse verified
   avrdude: reading input file "0xf7"
   avrdude: writing lfuse (1 bytes):
   
   Writing | ################################################## | 100% 0.01s
   
   avrdude: 1 bytes of lfuse written
   avrdude: verifying lfuse memory against 0xf7:
   avrdude: load data lfuse data from input file 0xf7:
   avrdude: input file 0xf7 contains 1 bytes
   avrdude: reading on-chip lfuse data:
   
   Reading | ################################################## | 100% 0.00s
   
   avrdude: verifying ...
   avrdude: 1 bytes of lfuse verified
   
   avrdude done.  Thank you.

If it's OK, just after burning the optiboot_flash bootloader, the on-board LED is blinking with a double fast flash, see the video on YouTube:

Test read/write flash memory at run-time

We use the SerialReadWrite sketch provided by MegaCore / Optiboot_flasher library which is installed, so:

• Open Arduino IDE and load Examples / Examples for ATmega2560 / Optiboot flash read/write / SerialReadWrite sketch

• Open Tools/Serial Monitor and upload the sketch

  

• Play with this sketch to write data in flash, power off/on the board and read back from flash to verifiy it's working.

Resources

• ./extras
• MCUdude / optiboot_flash
• MCUdude / MegaCore
• optiboot wiki
• Pololu USB AVR Programmer v2.1
• Pololu software
• ELEGOO MEGA 2560 R3 Board Blue

Author

Jean-Michel (Jim) FAURE (September 9th, 2020)

• company: FAURE SYSTEMS®
• mail: dev at faure dot systems
• github: fauresystems
• web: Faure●Systems