Configuration¶

Custom fuses¶

Custom fuse values and upload flags (based on upload protocol) should be specified in “platformio.ini” (Project Configuration File). lfuse and hfuse bits are mandatory, efuse is optional and not supported by all targets. An example of setting custom fuses for uno board:

[env:custom_fuses]
platform = atmelavr
framework = arduino
board = uno
upload_protocol = stk500v1
upload_speed = 19200
board_fuses.lfuse = 0xAA
board_fuses.hfuse = 0xBB
board_fuses.efuse = 0xCC
upload_flags =
    -PCOM15
    -b$UPLOAD_SPEED
    -e

MiniCore, MegaCore, MightyCore, MajorCore and MicroCore¶

MiniCore, MegaCore, MightyCore`, ``MajorCore` and ``MicroCore support dynamic fuses generation. Generated values are based on the next parameters:

Parameter	Description	Default value
board_build.f_cpu	Specifies the clock frequencies in Hz. Used to determine what oscillator option to choose. A capital L has to be added to the end of the frequency number.	16000000L
board_hardware.oscillator	Specifies which oscillator is used internal or external. Internal oscillator only works with f_cpu values 8000000L and 1000000L	external
board_hardware.uart	Specifies the hardware UART port used for serial upload. can be uart0, uart1, uart2 or uart3 depending on the target. Use no_bootloader if you’re not using a bootloader for serial upload.	uart0
board_hardware.bod	Specifies the hardware brown-out detection. Use disabled to disable brown-out detection.	2.7v
board_hardware.eesave	Specifies if the EEPROM memory should be retained when uploading using a programmer. Use no to disable	yes
board_hardware.ckout	Enables system clock output on targets that have this feature. The system clock will be output on a dedicated output pin. See the target datasheet for more information. Use Yes to enable	no
board_hardware.jtagen	Enables the JTAG programming and debugging interface for targets that supports JTAG. Use Yes to enable	no
board_hardware.cfd	Enables clock failure detection. Note that this feature is only available on ATmega324PB and ATmega328PB. Use Yes to enable CFD	no

Valid BOD values:

ATmega8, ATmega8515, ATmega8535/16/32, ATmega64/128	AT90CAN32/64/128	Other targets
4.0v	4.1v	4.3v
2.7v	4.0v	2.7v
disabled	3.9v	1.8v
	3.8v	disabled
	2.7v
	2.6v
	2.5v
	disabled

Hardware configuration example:

[env:custom_fuses]
platform = atmelavr
framework = arduino
board = ATmega32

board_build.f_cpu = 1000000L
board_hardware.uart = uart0
board_hardware.oscillator = internal
board_hardware.bod = 2.7v
board_hardware.eesave = no

upload_protocol = usbasp
upload_flags =
  -Pusb

Custom bootloader¶

Custom bootloader and corresponding fuses should be specified in “platformio.ini” (Project Configuration File). If lock_bits and unlock_bits are not set then the default values 0x0F and 0x3F are used accordingly. An example of setting custom bootloader for uno board:

[env:uno]
platform = atmelavr
framework = arduino
board = uno

board_bootloader.file = /path/to/custom/bootloader.hex
board_bootloader.lfuse = 0xFF
board_bootloader.hfuse = 0xDE
board_bootloader.efuse = 0xFD
board_bootloader.lock_bits = 0x0F
board_bootloader.unlock_bits = 0x3F

MiniCore, MegaCore, MightyCore and MajorCore have a wide variety of precompiled bootloaders. Bootloader binaries are dynamically selected according to the hardware parameters f_cpu, oscillator, uart and upload_speed. For a complete table with all available baud rates, see the Optiboot flash repo. Here is a table with recommended baud rates for different clock frequencies:

Frequency	Oscillator type	Recommended upload speed
20000000L	external	115200
18432000L	external	115200
16000000L	external	115200
14745600L	external	115200
12000000L	external	57600
11059200L	external	115200
8000000L	external/internal	57600/38400
7372800L	external	115200
4000000L	external	9600
3686400L	external	115200
2000000L	external	9600
1843200L	external	115200
1000000L	external/internal	9600