How to build for arduino with avr-gcc using a Makefile

gistfile1.txt

# simple makefile for avr-gcc projects

# what is the final binary called
PROGRAM = ddsvfo

# flags to pass to the C compiler
# -mmcu should be set to the CPU type
# -DF_CPU should be the clock speed in Hz
# you can add additional -D statements which work just like #define in the code
CFLAGS = -Wall -I. -g -Os -mmcu=atmega168 -DF_CPU=16000000

# Any other files that aren't C source, that trigger a rebuild
DEPS = lcd.h

# These are the object files that gcc will create, from your .c files
# you need one for each of your C source files
OBJ = vfo.o lcd.o analogue.o dds.o

# magic happens below here
# "make all" creates a burnable hex file
all: $(PROGRAM).hex

# this turns the .elf binary into .hex for avrdude
$(PROGRAM).hex: $(PROGRAM).elf
        avr-objcopy -O ihex $< $@

# this builds and links the .o files into a .elf binary
$(PROGRAM).elf: $(OBJ)
        avr-gcc $(CFLAGS) -o $@ $^

# this compiles the .c files into .o files
%.o: %.c $(DEPS)
        avr-gcc $(CFLAGS) -o $@ -c $<

# this calls the first macro we defined to create a .hex file
# then it runs avrdude to burn it to your Arduino

burn:   $(PROGRAM).hex
        avrdude -F -V -c arduino -p ATMEGA168 -P /dev/ttyUSB0 -b 19200 -U flash:w:$(PROGRAM).hex

clean:
        rm *.o
        rm *.elf
        rm *.hex

gistfile2.txt

// vim: set noexpandtab ai ts=4 sw=4 tw=4:
// vfo.c
// part of ddsvfo Copyright (C) 2013 Gordon JC Pearce MM0YEQ

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <avr/io.h>
#include <avr/interrupt.h>

// that's all you're getting.  You probably need at least avr/io.h for the pins to work
// as if by magic, -mmcu=atmega168 causes the includes to give you the correct definitions for that chip
// the vim modeline at the top is not important, it's just the way I like to use gedit