qmk_firmware/keyboards/zen/rules.mk

# Pro Micro or Elite-C
# Automagically converted to Proton-C
MCU = atmega32u4
F_CPU = 16000000
ARCH = AVR8
F_USB = $(F_CPU)
BOOTLOADER = dfu
OPT_DEFS += -DINTERRUPT_CONTROL_ENDPOINT

ifeq ($(strip $(CTPC)), yes)
  CONVERT_TO_PROTON_C=yes
endif

ifeq ($(strip $(CONVERT_TO_PROTON_C)), yes)
  SPLIT_KEYBOARD = no       # currently unsupported on ARM
  RGBLIGHT_ENABLE = no      # currently unsupported on ARM

  EXTRAFLAGS += -DUSE_PROTON_C
else
  # Currently moved to Pro Micro only section because of lack of Proton-C support
  SPLIT_KEYBOARD = yes
  RGBLIGHT_ENABLE = yes       # Enable WS2812 RGB underlight.
endif

# Build Options
#   change to "no" to disable the options, or define them in the Makefile in
#   the appropriate keymap folder that will get included automatically
#
BOOTMAGIC_ENABLE = no       # Virtual DIP switch configuration(+1000)
MOUSEKEY_ENABLE = yes       # Mouse keys(+4700)
EXTRAKEY_ENABLE = yes       # Audio control and System control(+450)
CONSOLE_ENABLE = no         # Console for debug(+400)
COMMAND_ENABLE = yes        # Commands for debug and configuration
NKRO_ENABLE = no            # Nkey Rollover - if this doesn't work, see here: https://github.com/tmk/tmk_keyboard/wiki/FAQ#nkro-doesnt-work
MIDI_ENABLE = no            # MIDI controls
AUDIO_ENABLE = no           # Audio output on port C6
UNICODE_ENABLE = no         # Unicode
BLUETOOTH_ENABLE = no       # Enable Bluetooth with the Adafruit EZ-Key HID

SLEEP_LED_ENABLE = no    # Breathing sleep LED during USB suspend

DEFAULT_FOLDER = zen/rev2