qmk_firmware/keyboards/ferris/0_1/rules.mk

# MCU name
MCU = atmega32u4

# Bootloader selection
BOOTLOADER = atmel-dfu

#   change yes to no to disable
#
BOOTMAGIC_ENABLE = no       # Virtual DIP switch configuration
MOUSEKEY_ENABLE = yes       # Mouse keys
EXTRAKEY_ENABLE = yes       # Audio control and System control
CONSOLE_ENABLE = no         # Console for debug
COMMAND_ENABLE = no         # Commands for debug and configuration
# Do not enable SLEEP_LED_ENABLE. it uses the same timer as BACKLIGHT_ENABLE
SLEEP_LED_ENABLE = no       # Breathing sleep LED during USB suspend
# if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
NKRO_ENABLE = no            # USB Nkey Rollover
BACKLIGHT_ENABLE = no       # Enable keyboard backlight functionality
RGBLIGHT_ENABLE = no        # Enable keyboard RGB underglow
BLUETOOTH_ENABLE = no       # Enable Bluetooth
AUDIO_ENABLE = no           # Audio output
UNICODE_ENABLE = yes
CUSTOM_MATRIX = lite
NO_USB_STARTUP_CHECK = yes
LTO_ENABLE = yes

SRC += matrix.c
QUANTUM_LIB_SRC += i2c_master.c