Arduino-Makefile/arduino-mk-vars.md

# Documentation of variables 

The following are the different variables that can be overwritten in the user makefiles.

- [Global variables](#global-variables)
- [Installation/Directory variables](#installationdirectory-variables)
- [Arduino IDE variables](#arduino-ide-variables)
- [Sketch related variables](#sketch-related-variables)
- [ISP programming variables](#isp-programming-variables)
- [Compiler/Executable variables](#compilerexecutable-variables)
- [Avrdude setting variables](#avrdude-setting-variables)
- [Bootloader variables](#bootloader-variables)
- [ChipKIT variables](#chipkit-variables)

## Global variables

### ARDUINO_QUIET
Suppress printing of Arduino-Makefile configuration.

Defaults to unset/disabled.

*Example*: 1

Optional.

## Installation/Directory variables

### ARDMK_DIR
Directory where the `*.mk` files are stored.

Usually can be auto-detected as `AUTO_ARDUINO_DIR` (parent of Arduino.mk).

*Example*: /usr/share/arduino

Optional.

### AVR_TOOLS_DIR
Directory where tools such as avrdude, avr-g++, avr-gcc etc. are stored in the bin/ subdirectory.

Usually can be auto-detected from `$PATH` as `SYSTEMPATH_AVR_TOOLS_DIR` or as `BUNDLED_AVR_TOOLS_DIR` within the Arduino distribution.

*Example*: /usr or /usr/share/arduino/hardware/tools/avr

Optional.

### RESET_CMD
Command to reset the MCU.

Defaults to ard-reset-arduino with the extra --caterina flag for atmega32u4 boards.

*Example*: ~/gertduino/reset

Optional.

## Arduino IDE variables

### ARDUINO_DIR
Directory where the Arduino IDE and/or core files are stored.

*Example*: /usr/share/arduino (Linux) or /Applications/Arduino.app/Contents/Resources/Java (OSX)

Optional.

### ARDUINO_VERSION
Version string for Arduino IDE and/or core.

Usually can be auto-detected as `AUTO_ARDUINO_VERSION` from /usr/share/arduino/lib/version.txt

*Example*: 105

Optional.

### ARDUINO_SKETCHBOOK
Path to sketchbook directory.

Usually can be auto-detected from the Arduino preferences.txt file or the default ~/sketchbook

*Example*: ~/sketches

Optional.

### ARDUINO_PREFERENCES_PATH
Path to Arduino preferences.txt file.

Usually can be auto-detected as `AUTO_ARDUINO_PREFERENCES` from the defaults ~/.arduino/preferences.txt (Linux) or ~/Library/Arduino/preferences.txt (OSX)

*Example*: ~/sketches/preferences.txt

Optional.

### ARDUINO_CORE_PATH
Path to standard Arduino core files.

*Example*: /usr/share/arduino/hardware/arduino/cores/arduino

Optional.

## Sketch related variables

### ARDUINO_LIBS
Any libraries you intend to include.

Usually can be auto-detected from the sketch. Separated by spaces. If the library has a /utility folder (like SD or Wire library), then the utility folder should also be specified.

*Example*: SD SD/utility Wire Wire/utility

Optional.

### BOARD_TAG
Device type as listed in boards.txt or `make show_boards`.

*Example*: uno or mega2560

Mandatory.

### MONITOR_PORT
Path to serial (USB) device used for uploading/serial comms.

*Example*: /dev/ttyUSB0 or /dev/ttyACM0 (Linux) or /dev/cu.usb* (OSX) or com3 (Windows)

Mandatory.

### USER_LIB_PATH
Directory where additional libraries are stored.

Defaults to 'libraries' directory within user's sketchbook.

*Example*: ~/sketchbook/libraries (Linux)

Optional.

### OBJDIR

**Description:**

Directory where binaries and compiled files are put.

Defaults to `build-$(BOARD_TAG)` in your `Makefile` directory.

**Example:**

```Makefile
OBJDIR = /path/to/my/project-directory/bin
```

**Status:** *Optional*

----

### ALTERNATE_CORE
Non-standard core for Arduino-unsupported chips like the ATtiny.

*Example*: attiny-master or arduino-tiny or tiny2

Optional.

### ARDUINO_VAR_PATH
Path to non-standard core's variant files.

*Example*: ~/sketchbook/hardware/arduino-tiny/cores/tiny

Optional.

### VARIANT
Variant of a standard board design.

Usually can be auto-detected as build.variant from boards.txt

*Example*: leonardo

Optional.

### USB_VID
Override USB VID for atmega32u4 boards.

Usually can be auto-detected as build.vid from boards.txt

*Example*: 0x2341

Optional.

### USB_PID
Override USB PID for atmega32u4 boards.

Usually can be auto-detected as build.pid from boards.txt

*Example*: 0x8039

Optional.

### F_CPU
CPU speed in Hz

Usually can be auto-detected as build.f_cpu from boards.txt

*Example*: 8000000L

Optional.

### HEX_MAXIMUM_SIZE
Maximum hex file size

Usually can be auto-detected as upload.maximum_size from boards.txt

*Example*: 14336

Optional.

### MCU
Microcontroller model.

Usually can be auto-detected as build.mcu from boards.txt

*Example*: atmega32u4

Optional.

### MCU_FLAG_NAME
Override default MCU flags.

Defaults to mmcu

*Example*: mprocessor

Optional.

### MONITOR_BAUDRATE
Baudrate of the serial monitor.

Defaults to 9600 if it can't find it in the sketch Serial.begin()

*Example*: 57600

Optional.

## ISP programming variables

### ISP_PROG
Type of ISP. Either a USB device or ArduinoISP protocol.

*Example*: usbasp or usbtiny or stk500v2 or stk500v1

Optional.

### ISP_PORT
Device path to ArduinoISP. Not needed for hardware ISP's.

*Example*: /dev/ttyACM0 (Linux)

Optional.

### ISP_LOCK_FUSE_PRE
Bootloader unlock bits.

Usually can be auto-detected from boards.txt

*Example*: 0x3f

Optional.

### ISP_LOCK_FUSE_POST
Bootloader lock bits.

Usually can be auto-detected from boards.txt

*Example*: 0xcf

Optional.

### ISP_HIGH_FUSE
SP_LOW_FUSE/ISP_EXT_FUSE - high/low/extended fuse bits.

Usually can be auto-detected from boards.txt

*Example*: 0xdf or 0xff or 0x01

Optional.

### ISP_EEPROM
Whether to upload the EEPROM file or not.

Defaults to 0

*Example*: 1

Optional.

## Compiler/Executable variables

### CC_NAME
C compiler.

Defaults to avr-gcc

*Example*: pic32-gcc

Optional.

### CXX_NAME
C++ compiler.

Defaults to avr-g++

*Example*: pic32-g++

Optional.

### OBJCOPY_NAME
Objcopy utility.

Defaults to avr-objcopy

*Example*: pic32-objcopy

Optional.

### OBJDUMP_NAME
Objdump utility.

Defaults to avr-objdump

*Example*: pic32-objdump

Optional.

### AR_NAME
Archive utility.

Defaults to avr-ar

*Example*: pic32-ar

Optional.

### SIZE_NAME
Size utility.

Defaults to avr-size

*Example*: pic32-size

Optional.

### NM_NAME
Nm utility.

Defaults to avr-nm

*Example*: pic32-nm

Optional.

### OPTIMIZATION_LEVEL
Linker's -O flag

Defaults to s, which shouldn't really be changed as it breaks SoftwareSerial and usually results in bigger hex files.

*Example*: 3

Optional.

### CFLAGS_STD
Flags to pass to the C compiler.

Defaults to -std=gnu99

*Example*: <unset as per chipKIT.mk>

Optional.

### OVERRIDE_EXECUTABLES
Override the default build tools.

If set to 1 each tool (CC, CXX, AS, OBJCOPY, OBJDUMP, AR, SIZE, NM) must have its path explicitly defined. See chipKIT.mk

*Example*: 1

Optional.

### MONITOR_CMD
Command to run the serial monitor.

Defaults to screen

*Example*: minicom

Optional.

## Avrdude setting variables

### AVRDUDE
Path to avrdude utility

Usually can be auto-detected within the parent of `AVR_TOOLS_DIR` or in the $PATH

*Example*: /usr/bin/avrdude

Optional.

### AVRDUDE_CONF
Path to avrdude.conf file

Usually can be auto-detected within the parent of `AVR_TOOLS_DIR` 

*Example*: /etc/avrdude.conf or /usr/share/arduino/hardware/tools/avrdude.conf

Optional.

### AVR_TOOLS_PATH
Directory where tools such as avrdude, avr-g++, avr-gcc etc. are stored.

Usually can be auto-detected from AVR_TOOLS_DIR/bin

*Example*: /usr/bin or /usr/share/arduino/hardware/tools/avr/bin

Optional.

### ARDUINO_LIB_PATH
Directory where the standard Arduino libraries are stored.

Defaults to ARDUINO_DIR/libraries

*Example*: /usr/share/arduino/libraries (Linux)

Optional.

### ARDUINO_CORE_PATH
Directory where the standard Arduino cores are stored.

Defaults to ARDUINO_DIR/hardware/arduino/cores/arduino

*Example*: /usr/share/arduino/hardware/arduino/cores/robot

Optional.

### ALTERNATE_CORE_PATH
Path to non-standard cores.

Defaults to ARDUINO_SKETCHBOOK/hardware/ALTERNATE_CORE

*Example*: ~/sketchbook/hardware/arduino-tiny/cores/tiny

Optional.

### BOARDS_TXT
Path to boards.txt

Defaults to ARDUINO_DIR/hardware/arduino/boards.txt

*Example*: ~/sketchbook/hardware/boards.txt or /usr/share/arduino/hardware/arduino/boards.txt (Linux)

Optional.

### AVRDUDE_ARD_BAUDRATE
Upload speed

Usually can be auto-detected as upload.speed from boards.txt

*Example*: 19200

Optional.

### AVRDUDE_ARD_PROGRAMMER
Upload protocol

Usually can be auto-detected as upload.protocol from boards.txt

*Example*: stk500v1

Optional.

### AVRDUDE_ISP_BAUDRATE
ISP speed if different to upload.speed

Defaults to same as `AVRDUDE_ARD_BAUDRATE` or 19200

*Example*: 19200

Optional.

### AVRDUDE_OPTS
Options to pass to avrdude.

Defaults to '-q -V -D' (quiet, don't verify, don't auto-erase). User values are not ANDed to the defaults, you have to set each option you require.

*Example*: -v

Optional.

## Bootloader variables

### BOOTLOADER_FILE
File for bootloader.

Usually can be auto-detected as bootloader.file from boards.txt

*Example*: optiboot_atmega328.hex

Optional.

### BOOTLOADER_PATH
Path to bootloader file.

Usually can be auto-detected as a relative bootloader.path from boards.txt

*Example*: optiboot or arduino:atmega or /usr/share/arduino/hardware/arduino/bootloaders/caterina/Caterina-Esplora.hex

Optional.

## ChipKIT variables

### MPIDE_DIR
Path to chipKIT MP IDE

Usually can be auto-detected as `AUTO_MPIDE_DIR` from the defaults /usr/share/mpide (Linux) or /Applications/Mpide.app/Contents/Resources/Java (OSX)

*Example*: ~/mpide

Optional.

### MPIDE_PREFERENCES_PATH
Path to chipKIT preferences.txt file.

Usually can be auto-detected as `AUTO_MPIDE_PREFERENCES_PATH` from the defaults ~/.mpide/preferences.txt (Linux) or ~/Library/Mpide/preferences.txt (OSX)

*Example*: ~/chipkit/preferences.txt

Optional.
Document all the variables that can be overridden in child makefile Huge thanks to @sej7278 for doing this Fix #75 2014-02-04 13:24:46 +01:00			`# Documentation of variables`

			`The following are the different variables that can be overwritten in the user makefiles.`

			`- [Global variables](#global-variables)`
			`- [Installation/Directory variables](#installationdirectory-variables)`
			`- [Arduino IDE variables](#arduino-ide-variables)`
			`- [Sketch related variables](#sketch-related-variables)`
			`- [ISP programming variables](#isp-programming-variables)`
			`- [Compiler/Executable variables](#compilerexecutable-variables)`
			`- [Avrdude setting variables](#avrdude-setting-variables)`
			`- [Bootloader variables](#bootloader-variables)`
			`- [ChipKIT variables](#chipkit-variables)`

			`## Global variables`

			`### ARDUINO_QUIET`
			`Suppress printing of Arduino-Makefile configuration.`

			`Defaults to unset/disabled.`

			`Example: 1`

			`Optional.`

			`## Installation/Directory variables`

			`### ARDMK_DIR`
			Directory where the `*.mk` files are stored.

			Usually can be auto-detected as `AUTO_ARDUINO_DIR` (parent of Arduino.mk).

			`Example: /usr/share/arduino`

			`Optional.`

			`### AVR_TOOLS_DIR`
			`Directory where tools such as avrdude, avr-g++, avr-gcc etc. are stored in the bin/ subdirectory.`

			Usually can be auto-detected from `$PATH` as `SYSTEMPATH_AVR_TOOLS_DIR` or as `BUNDLED_AVR_TOOLS_DIR` within the Arduino distribution.

			`Example: /usr or /usr/share/arduino/hardware/tools/avr`

			`Optional.`

			`### RESET_CMD`
			`Command to reset the MCU.`

			`Defaults to ard-reset-arduino with the extra --caterina flag for atmega32u4 boards.`

			`Example: ~/gertduino/reset`

			`Optional.`

			`## Arduino IDE variables`

			`### ARDUINO_DIR`
			`Directory where the Arduino IDE and/or core files are stored.`

			`Example: /usr/share/arduino (Linux) or /Applications/Arduino.app/Contents/Resources/Java (OSX)`

			`Optional.`

			`### ARDUINO_VERSION`
			`Version string for Arduino IDE and/or core.`

			Usually can be auto-detected as `AUTO_ARDUINO_VERSION` from /usr/share/arduino/lib/version.txt

			`Example: 105`

			`Optional.`

			`### ARDUINO_SKETCHBOOK`
			`Path to sketchbook directory.`

			`Usually can be auto-detected from the Arduino preferences.txt file or the default ~/sketchbook`

			`Example: ~/sketches`

			`Optional.`

			`### ARDUINO_PREFERENCES_PATH`
			`Path to Arduino preferences.txt file.`

			Usually can be auto-detected as `AUTO_ARDUINO_PREFERENCES` from the defaults ~/.arduino/preferences.txt (Linux) or ~/Library/Arduino/preferences.txt (OSX)

			`Example: ~/sketches/preferences.txt`

			`Optional.`

			`### ARDUINO_CORE_PATH`
			`Path to standard Arduino core files.`

			`Example: /usr/share/arduino/hardware/arduino/cores/arduino`

			`Optional.`

			`## Sketch related variables`

			`### ARDUINO_LIBS`
			`Any libraries you intend to include.`

			`Usually can be auto-detected from the sketch. Separated by spaces. If the library has a /utility folder (like SD or Wire library), then the utility folder should also be specified.`

			`Example: SD SD/utility Wire Wire/utility`

			`Optional.`

			`### BOARD_TAG`
			Device type as listed in boards.txt or `make show_boards`.

			`Example: uno or mega2560`

			`Mandatory.`

			`### MONITOR_PORT`
			`Path to serial (USB) device used for uploading/serial comms.`

			`Example: /dev/ttyUSB0 or /dev/ttyACM0 (Linux) or /dev/cu.usb* (OSX) or com3 (Windows)`

			`Mandatory.`

			`### USER_LIB_PATH`
			`Directory where additional libraries are stored.`

			`Defaults to 'libraries' directory within user's sketchbook.`

			`Example: ~/sketchbook/libraries (Linux)`

			`Optional.`

Add OBJDIR reference Signed-off-by: tinyladi <ladislas@weareleka.com> 2014-02-27 22:22:59 +01:00			`### OBJDIR`

			`Description:`

			`Directory where binaries and compiled files are put.`

			Defaults to `build-$(BOARD_TAG)` in your `Makefile` directory.

			`Example:`

			```Makefile
			`OBJDIR = /path/to/my/project-directory/bin`
			```

			`Status: Optional`

			`----`

Document all the variables that can be overridden in child makefile Huge thanks to @sej7278 for doing this Fix #75 2014-02-04 13:24:46 +01:00			`### ALTERNATE_CORE`
			`Non-standard core for Arduino-unsupported chips like the ATtiny.`

			`Example: attiny-master or arduino-tiny or tiny2`

			`Optional.`

			`### ARDUINO_VAR_PATH`
			`Path to non-standard core's variant files.`

			`Example: ~/sketchbook/hardware/arduino-tiny/cores/tiny`

			`Optional.`

			`### VARIANT`
			`Variant of a standard board design.`

			`Usually can be auto-detected as build.variant from boards.txt`

			`Example: leonardo`

			`Optional.`

			`### USB_VID`
			`Override USB VID for atmega32u4 boards.`

			`Usually can be auto-detected as build.vid from boards.txt`

			`Example: 0x2341`

			`Optional.`

			`### USB_PID`
			`Override USB PID for atmega32u4 boards.`

			`Usually can be auto-detected as build.pid from boards.txt`

			`Example: 0x8039`

			`Optional.`

			`### F_CPU`
			`CPU speed in Hz`

			`Usually can be auto-detected as build.f_cpu from boards.txt`

			`Example: 8000000L`

			`Optional.`

			`### HEX_MAXIMUM_SIZE`
			`Maximum hex file size`

			`Usually can be auto-detected as upload.maximum_size from boards.txt`

			`Example: 14336`

			`Optional.`

			`### MCU`
			`Microcontroller model.`

			`Usually can be auto-detected as build.mcu from boards.txt`

			`Example: atmega32u4`

			`Optional.`

			`### MCU_FLAG_NAME`
			`Override default MCU flags.`

			`Defaults to mmcu`

			`Example: mprocessor`

			`Optional.`

			`### MONITOR_BAUDRATE`
			`Baudrate of the serial monitor.`

			`Defaults to 9600 if it can't find it in the sketch Serial.begin()`

			`Example: 57600`

			`Optional.`

			`## ISP programming variables`

			`### ISP_PROG`
			`Type of ISP. Either a USB device or ArduinoISP protocol.`

			`Example: usbasp or usbtiny or stk500v2 or stk500v1`

			`Optional.`

			`### ISP_PORT`
			`Device path to ArduinoISP. Not needed for hardware ISP's.`

			`Example: /dev/ttyACM0 (Linux)`

			`Optional.`

			`### ISP_LOCK_FUSE_PRE`
			`Bootloader unlock bits.`

			`Usually can be auto-detected from boards.txt`

			`Example: 0x3f`

			`Optional.`

			`### ISP_LOCK_FUSE_POST`
			`Bootloader lock bits.`

			`Usually can be auto-detected from boards.txt`

			`Example: 0xcf`

			`Optional.`

			`### ISP_HIGH_FUSE`
			`SP_LOW_FUSE/ISP_EXT_FUSE - high/low/extended fuse bits.`

			`Usually can be auto-detected from boards.txt`

			`Example: 0xdf or 0xff or 0x01`

			`Optional.`

			`### ISP_EEPROM`
			`Whether to upload the EEPROM file or not.`

			`Defaults to 0`

			`Example: 1`

			`Optional.`

			`## Compiler/Executable variables`

			`### CC_NAME`
			`C compiler.`

			`Defaults to avr-gcc`

			`Example: pic32-gcc`

			`Optional.`

			`### CXX_NAME`
			`C++ compiler.`

			`Defaults to avr-g++`

			`Example: pic32-g++`

			`Optional.`

			`### OBJCOPY_NAME`
			`Objcopy utility.`

			`Defaults to avr-objcopy`

			`Example: pic32-objcopy`

			`Optional.`

			`### OBJDUMP_NAME`
			`Objdump utility.`

			`Defaults to avr-objdump`

			`Example: pic32-objdump`

			`Optional.`

			`### AR_NAME`
			`Archive utility.`

			`Defaults to avr-ar`

			`Example: pic32-ar`

			`Optional.`

			`### SIZE_NAME`
			`Size utility.`

			`Defaults to avr-size`

			`Example: pic32-size`

			`Optional.`

			`### NM_NAME`
			`Nm utility.`

			`Defaults to avr-nm`

			`Example: pic32-nm`

			`Optional.`

			`### OPTIMIZATION_LEVEL`
			`Linker's -O flag`

			`Defaults to s, which shouldn't really be changed as it breaks SoftwareSerial and usually results in bigger hex files.`

			`Example: 3`

			`Optional.`

			`### CFLAGS_STD`
			`Flags to pass to the C compiler.`

			`Defaults to -std=gnu99`

			`Example: <unset as per chipKIT.mk>`

			`Optional.`

			`### OVERRIDE_EXECUTABLES`
			`Override the default build tools.`

			`If set to 1 each tool (CC, CXX, AS, OBJCOPY, OBJDUMP, AR, SIZE, NM) must have its path explicitly defined. See chipKIT.mk`

			`Example: 1`

			`Optional.`

			`### MONITOR_CMD`
			`Command to run the serial monitor.`

			`Defaults to screen`

			`Example: minicom`

			`Optional.`

			`## Avrdude setting variables`

			`### AVRDUDE`
			`Path to avrdude utility`

			Usually can be auto-detected within the parent of `AVR_TOOLS_DIR` or in the $PATH

			`Example: /usr/bin/avrdude`

			`Optional.`

			`### AVRDUDE_CONF`
			`Path to avrdude.conf file`

			Usually can be auto-detected within the parent of `AVR_TOOLS_DIR`

			`Example: /etc/avrdude.conf or /usr/share/arduino/hardware/tools/avrdude.conf`

			`Optional.`

			`### AVR_TOOLS_PATH`
			`Directory where tools such as avrdude, avr-g++, avr-gcc etc. are stored.`

			`Usually can be auto-detected from AVR_TOOLS_DIR/bin`

			`Example: /usr/bin or /usr/share/arduino/hardware/tools/avr/bin`

			`Optional.`

			`### ARDUINO_LIB_PATH`
			`Directory where the standard Arduino libraries are stored.`

			`Defaults to ARDUINO_DIR/libraries`

			`Example: /usr/share/arduino/libraries (Linux)`

			`Optional.`

			`### ARDUINO_CORE_PATH`
			`Directory where the standard Arduino cores are stored.`

			`Defaults to ARDUINO_DIR/hardware/arduino/cores/arduino`

			`Example: /usr/share/arduino/hardware/arduino/cores/robot`

			`Optional.`

			`### ALTERNATE_CORE_PATH`
			`Path to non-standard cores.`

			`Defaults to ARDUINO_SKETCHBOOK/hardware/ALTERNATE_CORE`

			`Example: ~/sketchbook/hardware/arduino-tiny/cores/tiny`

			`Optional.`

			`### BOARDS_TXT`
			`Path to boards.txt`

			`Defaults to ARDUINO_DIR/hardware/arduino/boards.txt`

			`Example: ~/sketchbook/hardware/boards.txt or /usr/share/arduino/hardware/arduino/boards.txt (Linux)`

			`Optional.`

			`### AVRDUDE_ARD_BAUDRATE`
			`Upload speed`

			`Usually can be auto-detected as upload.speed from boards.txt`

			`Example: 19200`

			`Optional.`

			`### AVRDUDE_ARD_PROGRAMMER`
			`Upload protocol`

			`Usually can be auto-detected as upload.protocol from boards.txt`

			`Example: stk500v1`

			`Optional.`

			`### AVRDUDE_ISP_BAUDRATE`
			`ISP speed if different to upload.speed`

			Defaults to same as `AVRDUDE_ARD_BAUDRATE` or 19200

			`Example: 19200`

			`Optional.`

			`### AVRDUDE_OPTS`
			`Options to pass to avrdude.`

			`Defaults to '-q -V -D' (quiet, don't verify, don't auto-erase). User values are not ANDed to the defaults, you have to set each option you require.`

			`Example: -v`

			`Optional.`

			`## Bootloader variables`

			`### BOOTLOADER_FILE`
			`File for bootloader.`

			`Usually can be auto-detected as bootloader.file from boards.txt`

			`Example: optiboot_atmega328.hex`

			`Optional.`

			`### BOOTLOADER_PATH`
			`Path to bootloader file.`

			`Usually can be auto-detected as a relative bootloader.path from boards.txt`

			`Example: optiboot or arduino:atmega or /usr/share/arduino/hardware/arduino/bootloaders/caterina/Caterina-Esplora.hex`

			`Optional.`

			`## ChipKIT variables`

			`### MPIDE_DIR`
			`Path to chipKIT MP IDE`

			Usually can be auto-detected as `AUTO_MPIDE_DIR` from the defaults /usr/share/mpide (Linux) or /Applications/Mpide.app/Contents/Resources/Java (OSX)

			`Example: ~/mpide`

			`Optional.`

			`### MPIDE_PREFERENCES_PATH`
			`Path to chipKIT preferences.txt file.`

			Usually can be auto-detected as `AUTO_MPIDE_PREFERENCES_PATH` from the defaults ~/.mpide/preferences.txt (Linux) or ~/Library/Mpide/preferences.txt (OSX)

			`Example: ~/chipkit/preferences.txt`

			`Optional.`