PlatformIO

April 19, 2026 · View on GitHub

PlatformIO is an open-source ecosystem for embedded development. It has a built-in library manager and is Arduino-compatible. It supports most operating systems; Windows, MacOS, Linux 32 and 64-bit, ARM, and X86.
And best of all, MiniCore is supported!

What is PlatformIO?
PlatformIO IDE
Getting started with PlatformIO IDE or PlatformIO command line interface
Advanced functionality
Project Examples

MiniCore + PlatformIO

MiniCore and PlatformIO go great together. You can do serial uploads and upload using a dedicated programmer, but you can also let PlatformIO calculate the fuses and load the correct bootloader file, just like Arduino IDE does!

PlatformIO uses the information provided in platformio.ini to calculate what fuse bits and what bootloader file to load.
Provide enough information and run the following commands:

; Only set fuses
pio run -t fuses -e fuses_bootloader
; Set fuses and burn bootloader
pio run -t bootloader -e fuses_bootloader
; (where "fuses_bootloader" can be replaced with a different environment to match your build configuration)

You can find a platformio.ini template you can use when creating a project for a MiniCore-compatible device below.
The most common functionality is available in this template. As you can see, the template is divided into multiple environments.

The default build environment is defined under [platformio].
All parameters common for all environments are defined under [env].
Use [env:Upload_UART] or [env:Upload_ISP] to upload to your target.
Use [env:fuses_bootloader] to set the fuses or burn the bootloader.

More information on what each line means can be found further down on this page.

platformio.ini template

; PlatformIO Project Configuration File for MiniCore
; https://github.com/MCUdude/MiniCore/
;
;   Build options: build flags, source filter
;   Upload options: custom upload port, speed, and extra flags
;   Library options: dependencies, extra library storage
;   Advanced options: extra scripting
;
; Please visit the documentation for the other options
; https://github.com/MCUdude/MiniCore/blob/master/PlatformIO.md
; https://docs.platformio.org/page/projectconf.html


[platformio]
default_envs = Upload_UART ; Default build target


; Common settings for all environments
[env]
platform = atmelavr
framework = arduino

; TARGET SETTINGS
; Chip in use
board = ATmega328P
; Clock frequency in [Hz]
board_build.f_cpu = 16000000L

; BUILD OPTIONS
; Comment out to enable LTO (this line unflags it)
build_unflags = -flto
; Extra build flags
build_flags = 

; SERIAL MONITOR OPTIONS
; Serial monitor port defined in the Upload_UART environment
monitor_port = ${env:Upload_UART.upload_port}
; Serial monitor baud rate
monitor_speed = 9600


; Run the following command to upload with this environment
; pio run -e Upload_UART -t upload
[env:Upload_UART]
; Serial bootloader protocol
upload_protocol = urclock
; Serial upload port
upload_port = /dev/cu.usbserial*
; Set upload baudrate. Can be changed on the fly if using Urboot
board_upload.speed = ${env:fuses_bootloader.board_bootloader.speed}


; Run the following command to upload with this environment
; pio run -e Upload_ISP -t upload
[env:Upload_ISP]
; Custom upload procedure
upload_protocol = custom
; Avrdude upload flags
upload_flags =
  -C$PROJECT_PACKAGES_DIR/tool-avrdude/avrdude.conf
  -p$BOARD_MCU
  -cusbasp
; Avrdude upload command
upload_command = avrdude $UPLOAD_FLAGS -U flash:w:$SOURCE:i


; Run the following command to set fuses
; pio run -e fuses_bootloader -t fuses
; Run the following command to set fuses + burn bootloader
; pio run -e fuses_bootloader -t bootloader
[env:fuses_bootloader]
board_hardware.oscillator = external ; Oscillator type
board_bootloader.type = urboot       ; urboot, optiboot or no_bootloader
board_bootloader.speed = 115200      ; Bootloader baud rate
board_hardware.uart = uart0          ; Set UART to use for serial upload
board_hardware.bod = 2.7v            ; Set brown-out detection
board_hardware.eesave = yes          ; Preserve EEPROM when uploading using programmer
upload_protocol = usbasp             ; Use the USBasp as programmer
upload_flags =                       ; Select USB as upload port and divide the SPI clock by 8
  -B8

`board`

PlatformIO requires the board parameter to be present. The table below shows what board name should be used for each target

Target	Board name
ATmega328PB	`ATmega328PB`
ATmega328P/PA	`ATmega328P`
ATmega328	`ATmega328`
ATmega168PB	`ATmega168PB`
ATmega168P/PA	`ATmega168P`
ATmega168/A	`ATmega168`
ATmega88PB	`ATmega88PB`
ATmega88P/PA	`ATmega88P`
ATmega88/A	`ATmega88`
ATmega48PB	`ATmega48PB`
ATmega48P/PA	`ATmega48P`
ATmega48/A	`ATmega48`
ATmega8/A	`ATmega8`

`board_build.f_cpu`

Specifies the clock frequency in [Hz]. Used to determine what oscillator option to choose. A capital L has to be added to the end of the frequency number. Below is a table with supported clocks. Defaults to 16 MHz if not specified.

Clock speed	Oscillator	board_build.f_cpu
20 MHz	External	`20000000L`
18.432 MHz	External	`18432000L`
16 MHz	External	`16000000L` (default)
14.7456 MHz	External	`14745600L`
12 MHz	External	`12000000L`
11.0592 MHz	External	`11059200L`
9.216 MHz	External	`9216000L`
8 MHz	External	`8000000L`
7.3728 MHz	External	`7372800L`
6 MHz	External	`6000000L`
4 MHz	External	`4000000L`
3.6864 MHz	External	`3686400L`
2 MHz	External	`2000000L`
1.8432 MHz	External	`1843200L`
1 MHz	External	`1000000L`
8 MHz	Internal	`8000000L`
1 MHz	Internal	`1000000L`

`board_hardware.oscillator`

Specifies to use the internal or an external oscillator.
Internal oscillator only works with board_build.f_cpu values 8000000L and 1000000L.

Oscillator option
`external` (default)
`internal`

`board_bootloader.type`

Specifies which bootloader type to burn.

Bootloader type
`urboot` (default)
`optiboot` (deprecated)
`no_bootlaoder`

`board_hardware.uart`

Specifies the hardware UART port used for serial upload. Use no_bootloader if you’re using a dedicated programmer, i.e. not using a bootloader for serial upload.

Upload serial port option
`no_bootloader`
`uart0` (default)
`uart1` (328PB only)

`board_hardware.bod`

Specifies the hardware brown-out detection. Use disabled to disable.

ATmega48/88/168/328	ATmega8
`4.3v`	`4.0v`
`2.7v` (default)	`2.7v` (default)
`1.8v`
`disabled`	`disabled`

`board_hardware.eesave`

Specifies if the EEPROM memory should be retained when uploading using a programmer. Use no to disable.

EEPROM retain
`yes` (default)
`no`

`board_hardware.ckout`

Enable clock output on pin PB0 on targets that support it (ATmega48/88/168/328).

Clock output enable
`yes`
`no` (default)

`board_hardware.cfd`

Enable clock failure detection. The internal 1 MHz oscillator will kick in if the external oscillator fails (only available on ATmega328PB).

Clock failure detection
`yes`
`no` (default)

`board_upload.speed` / `board_bootloader.speed`

Specifies the upload baud rate. Valid baud rates are shown in the table below. The Urboot bootloader has auto baud support, so the upload baud rate can be changed without re-flashing the bootloader. Optiboot on the other hand is compiled to support a specific baud rate, and a different bootloader binary needs to be flashed to support a different baud rate.

Note that if you're using a programmer that communicates with Avrdude with a serial port (Arduino as ISP, STK500, etc.) the board_upload.speed field will interfere with the programmer's baud rate.
In this case, use board_bootloader.speed to set the bootloader baud rate, and board_upload.speed to set the baud rate for the programmer.

Suggested baud rates for a particular clock speed are in bold text.

	1000000	500000	460800	250000	230400	115200	57600	38400	19200	9600
`20000000L`		X		X		X			X
`18432000L`			X		X	X	X	X	X	X
`16000000L`	X	X		X		X		X	X	X
`14745600L`			X		X	X	X	X	X	X
`12000000L`		X		X			X		X	X
`11059200L`			X		X	X	X	X	X	X
`9216000L`					X	X	X	X	X	X
`8000000L`	X	X		X		X	X	X	X	X
`7372800L`			X		X	X	X	X	X	X
`6000000L`				X			X	X	X	X
`4000000L`		X							X	X
`3686400L`			X		X	X	X	X	X	X
`2000000L`				X					X	X
`1843200L`					X	X	X	X	X	X
`1000000L`										X

`build_unflags`

This parameter is used to unflag. Since LTO is enabled by default in PlatformIO we may disable it by unflagging -flto.

`build_flags`

This parameter is used to set compiler flags. This is useful if you want to, for instance, change the serial RX or TX buffer. Here's a list of the currently available core files flags:

Flag	Default size	Description
-lprintf_flt		Lets you print floats with printf (occupies ~1.5 kB)
-Wall -Wextra		Show all compiler warnings
-DSERIAL_RX_BUFFER_SIZE=128	64 bytes	Sets the serial RX buffer to 128 bytes
-DSERIAL_TX_BUFFER_SIZE=128	64 bytes	Sets the serial TX buffer to 128 bytes
-DTWI_BUFFER_SIZE=64	32 bytes	Sets the TWI (i2c) buffer to 64 bytes
-DTWI1_BUFFER_SIZE=64	32 bytes	Sets the TWI1 (i2c) buffer to 64 bytes (ATmega328PB only)
-DWIRE_TIMEOUT		Enable timeout for the Wire and Wire1 library

Example: build_flags = -DSERIAL_RX_BUFFER_SIZE=128 -DSERIAL_TX_BUFFER_SIZE=128

`upload_port`

Specifies the serial port used for uploading. PlatformIO automatically detects the serial port. However, if you want to override this you can uncomment upload_port. Use /dev/[port] on Unix-compatible systems, and use COMx on Windows.

`upload_protocol`

Used when using a programmer rather than using a USB to serial adapter.
Supports all Avrdude compatible programmers such as usbasp, usbtiny and stk500v1.

`upload_flags`

Used to pass extra flags to Avrdude when uploading using a programmer.
Typical parameters are -PUSB, -B[clock divider] and -b[baudrate].
Note that every flag has to be on its own line, and they have to be indented with two spaces:

upload_flags =
  -PUSB
  -B32
  -v

`monitor_port`

PlatformIO detects serial ports automatically. However, In the template above it uses the upload port defined in the env:Upload_UART environment. if you want to override this you can insert your upload port here. Use /dev/[port] on Unix-compatible systems, and use COMx on Windows.

`monitor_speed`

Sets the serial monitor baud rate. Defaults to 9600 if not defined.