Barebones Blinky for Arduino Nano over USB

main.c

#include "Arduino.h"

int main () {

  init ();

  pinMode (13, OUTPUT);

  for (;;) {
    digitalWrite (13, HIGH);
    delay (100);

    digitalWrite (13, LOW);
    delay (100);
  }

}

Makefile

ARDUINO_DIR = /usr/share/arduino/hardware/arduino
ARDUINO_CORE_DIR = $(ARDUINO_DIR)/cores/arduino

ARCH = atmega328p

CORE_SRC = \
	$(ARDUINO_CORE_DIR)/wiring.c \
	$(ARDUINO_CORE_DIR)/wiring_digital.c

.PHONY: all
all: main.elf

.PHONY: clean
clean:
	-rm -f main.elf

.PHONY: install
install: main.elf
	avrdude -p $(ARCH) -c arduino -P /dev/ttyUSB0 -b 57600 -D -U flash:w:$<

main.elf: main.c $(CORE_SRC)
	avr-gcc -mmcu=$(ARCH) -DF_CPU=16000000L \
		-I $(ARDUINO_CORE_DIR) \
		-I $(ARDUINO_DIR)/variants/eightanaloginputs \
		-o $@ $^