Update the firmware of Arduino boards based on Atmel AVR

arduino, flash, bootloader, upgrade
pip install arduinobootloader==0.0.6



PyArduinoFlash is an open source library in Python for updating the firmware of Arduino boards that use the ATmegaBOOT_168 or Arduino Stk500V2 bootloader, for example Arduino Nano or Arduino Uno or Arduino Mega 2560 and many more.

The intention is to have a class that can be imported into any python project to update the Arduinos through the serial port.

It implements a subset of Atmel's STK-500V1 and STK500V2 protocol, using as reference the protocols implemented by Avrdude in the arduino.c and wiring.c modules.

For Arduino's using Atmel AVR8 processors there are three versions of the bootoloader available. For boards that have less than 128 Kbytes of Flash memory, for example Nano or Uno using the Atmega328P, etc that are marked in the Arduino IDE as older you have to use STK500-V1 at 57600 baud. And for the new ones (they implement the Optiboot bootloader) you have to use STK500-V1 at 115200 baud. For boards that have processors of more than 128 Kbytes, for example the Mega 2560, STK500-V2 must be used at 115200 baud.

As an example of use, there is an APP in KivyMd and Kivy that exposes through a GUI all the methods required to update and verify the firmware.

The first example shows the upgrade of a Nano board with a new bootolader. Select STK500-V1 at 115200 baud.

The second example shows the upgrade of a Mega board with 2560 processor. STK500-V2 must be selected at 115200 baud.


Install using pip or pip3 (recommended, no separate download required):

pip install arduinobootloader

Documentation and Examples

    from intelhex import IntelHex
    from arduinobootloader import ArduinoBootloader

    ih = IntelHex()
    ab = ArduinoBootloader()
    prg = ab.select_programmer("Stk500v1")

        if not prg.board_request():
        print("botloader name: {} version: {} hardware: {}".format(ab.programmer_name, ab.sw_version, ab.hw_version))
        if not prg.cpu_signature():
        print("cpu name: {}".format(ab.cpu_name) )
        ih.fromfile("firmware_file.hex", format='hex')
        for address in range(0, ih.maxaddr(), ab.cpu_page_size):
            buffer = ih.tobinarray(start=address, size=ab.cpu_page_size)
            if not prg.write_memory(buffer, address):
               print("Write error") 
        for address in range(0, ih.maxaddr(), ab.cpu_page_size):
            buffer = ih.tobinarray(start=address, size=ab.cpu_page_size)
            read_buffer = prg.read_memory(address, ab.cpu_page_size)
            if not len(read_buffer):
               print("Read error") 
            if buffer != read_buffer:
               print("File not match")

The parsing of the file in Intel hexadecimal format is done with the IntelHex library.

To have an instance of the class use ab = ArduinoBootloader() The next step is to select the programmer protocol prg = ab.select_protocol("Stk500v1") . To establish the connection with the bootloader of the Arduino board use that returns True when it is successful.

As the library needs the information of the CPU to know the size of the page, it is necessary to use the functions prg.board_request() and prg.cpu_signature()

If the previous functions were executed successfully (they return True), now you have to open the hexadecimal file with the ih.fromfile("firmware_file.hex", format='hex') function. If there are errors in the format or the file path is invalid, exceptions are thrown.

To obtain the page that corresponds to the current address, use the ih.tobinarray(start=address, size=ab.cpu_page_size) .

For the bootloader to write it, use the function prg.write_memory(buffer, address) which take the buffer and the current address as parameters. Returns True when completed successfully.

The reading to verify the recording is done in the same way, with the exception that the function returns the buffer read. If it is None it indicates that there were problems.

The bootloader begins the execution of the firmware after a period of time without receiving communication; nevertheless it is convenient to execute the function prg.leave_bootloader().

Finally, to release the serial port, you have to execute the function prg.close().


The Script folder contains file that allows update or read the firmware of Arduino boards.

One of the purposes is to show the use of the PyArduinoBootloader library in conjunction with the IntelHex library to process hexadecimal files.

Use the argparse library, to read the command line (file and options).

And to indicate the progress the progressbar2 library.

usage: [-h] [--version] [-r | -u] filename

arduino flash utility

positional arguments:
  filename      filename in hexadecimal Intel format

optional arguments:
  -h, --help    show this help message and exit
  --version     script version
  -b BAUDRATE, --baudrate BAUDRATE
                        old bootolader (57600) Optiboot (115200)
  -p PROGRAMMER, --programmer PROGRAMMER
                        programmer version - Nano (Stk500v1) Mega (Stk500v2)
  -r, --read            read the cpu flash memory
  -u, --update          update cpu flash memory

The following capture shows the reading of the flash memory of an Arduino Nano board.

And the next shows the firmware update of an Arduino Nano board.

The following capture shows the reading of the flash memory of an Arduino Mega 2560 board.

And the next shows the firmware update of an Arduino Mega 2560 board.


If you need assistance, contact me:



  • PyArduinoFlash is released under the terms of the MIT License. Please refer to the LICENSE file.