#============= MCU选择 ===========================
# MCU name
MCU = atmega8

#============= 输出格式选择 ======================
# Output format. (can be srec, ihex)
FORMAT = ihex

#============= 目标文件名(不带扩展名) ============
# Target file name (without extension).
TARGET = main

#============= 优化级别选择 ======================
# Optimization level (can be 0, 1, 2, 3, s)
# (Note: 3 is not always the best optimization level. See avr-libc FAQ)
OPT = s

#============= C 源文件列表("\"为换行符号) =======
# List C source files here. (C dependencies are automatically generated.)
SRC = $(TARGET).c timer.c extdrv.c adc.c sd2k.c mylib.c

#============= ASM 源文件列表 ====================
# List Assembler source files here.
ASRC =

#============= C编译选项 =========================
# Optional compiler flags.
CFLAGS = -g -O$(OPT) -funsigned-char -funsigned-bitfields -fpack-struct -fshort-enums -Wall -Wstrict-prototypes -Wa,-ahlms=$(<:.c=.lst)

#============= 汇编器选项 ========================
# Optional assembler flags.
ASFLAGS = -Wa,-ahlms=$(<:.s=.lst), -gstabs

#============= 连接器选项 ========================
# Optional linker flags.
LDFLAGS = -Wl,-Map=$(TARGET).map,--cref

#============= 附加库选项 ========================
# Additional library flags (-lm = math library).
LIBFLAGS = -lm

#***********************************************************************************
# WinAVR Sample makefile (c) 2002-2003 Eric B. Weddington
# Released to the Public Domain
# Please read the make user manual!
#
# On command line:
# make all = Make software. 编译
# make clean = Clean out built project files. 清除以前编译生成的文件
# make coff = Convert ELF to COFF using objtool. 转换elf文件为cof文件
#
# To rebuild project do make clean then make all.
#
#***********************************************************************************

#============= 指定目录，如果需要 ================
# Define directories, if needed.
DIRAVR = c:/ele/winavr
DIRAVRBIN = $(DIRAVR)/bin
DIRAVRUTILS = $(DIRAVR)/utils/bin
DIRINC = .
DIRLIB = $(DIRAVR)/avr/lib

#============= 定义命令(工具软件名称) ============
# Define programs and commands.
SHELL = sh
CC = avr-gcc
OBJCOPY = avr-objcopy
OBJDUMP = avr-objdump
REMOVE = rm -f
COPY = cp
ELFCOFF = objtool

#============= 一些字符串的定义和数据的取得 =======
HEXSIZE = @avr-size --target=$(FORMAT) $(TARGET).hex
ELFSIZE = @avr-size $(TARGET).elf

FINISH = @echo Errors: none
BEGIN = @echo -------- begin --------
END = @echo --------  end  --------

#============== 指定所有的连接文件 ================
# Define all object files.
OBJ = $(SRC:.c=.o) $(ASRC:.s=.o)

#============== 指定所有的列表文件 ================
# Define all listing files.
LST = $(ASRC:.s=.lst) $(SRC:.c=.lst)

#============== 指定全部.d文件 ====================
# Define all listing files.
ALLD = $(SRC:.c=.d) $(ASRC:.c=.d)

#============== 编译所有可选的和必须的选项标志，增加处理标志 =
# Combine all necessary flags and optional flags. Add target processor to flags.
ALL_CFLAGS = -mmcu=$(MCU) -I. $(CFLAGS)
ALL_ASFLAGS = -mmcu=$(MCU) -I. -x assembler-with-cpp $(ASFLAGS)
ALL_LDFLAGS = -mmcu=$(MCU) $(LDFLAGS)

#============== 默认的处理(指执行make时，相当于执行make all),真正的编译过程,超级重要,要看懂!!! ==
# Default target.
all: begin gccversion sizebefore $(TARGET).elf $(TARGET).hex $(TARGET).eep $(TARGET).lss $(TARGET).cof sizeafter finished end
#    开始->gcc版权信息>旧文件大小>编译生成.elf----->生成.hex----->生成.eep----->生成.lss----->生成.cof>新文件大小--->完成>结束

#***********************************************************************************
#============== 待输出的一些编译信息 =============
# Eye candy.
begin:
    $(BEGIN)

finished:
    $(FINISH)

end:
    $(END)

#============== 显示文件的大小信息(先前的和之后的) ==
# Display size of file.
sizebefore:
    @echo Size before:
    -$(HEXSIZE)

sizeafter:
    @echo Size after:
    $(HEXSIZE)

#=============== 显示编译版本信息 ===================
# Display compiler version information.
gccversion :
    $(CC) --version

#=============== 功能：转换ELF文件为COFF文件，以便在AVR Studio 中仿真/调试。==
# Target: Convert ELF to COFF for use in debugging / simulating in AVR Studio.
coff: $(TARGET).cof end
%.cof: %.elf
    $(ELFCOFF) loadelf $< mapfile $*.map writecof $@

#=============== 从ELF输出文件中生成最终的输出文件(.hex,.eep) ==
# Create final output files (.hex, .eep) from ELF output file.
%.hex: %.elf
    $(OBJCOPY) -O $(FORMAT) -R .eeprom $< $@

%.eep: %.elf
    -$(OBJCOPY) -j .eeprom --set-section-flags=.eeprom="alloc,load" --change-section-lma .eeprom=0 -O $(FORMAT) $< $@
    
#=============== 从ELF输出文件中生成扩充的列表文件(.lss) ==
# Create extended listing file from ELF output file.
%.lss: %.elf
    $(OBJDUMP) -h -S $< > $@

#=============== 连接：从OBJ文件中生成ELF文件(.elf) ==
# Link: create ELF output file from object files.
.SECONDARY : $(TARGET).elf
.PRECIOUS : $(OBJ)
%.elf: $(OBJ)
    $(CC) $(ALL_LDFLAGS) $(OBJ) $(LIBFLAGS) --output $@

#=============== 编译：从C源文件中生成OBJ文件(.o) ==
# Compile: create object files from C source files.
%.o : %.c
    $(CC) -c $(ALL_CFLAGS) $< -o $@

#=============== 汇编：从汇编源文件中生成OBJ文件(.o) ==
# Assemble: create object files from assembler source files.
%.o : %.s
    $(CC) -c $(ALL_ASFLAGS) $< -o $@

3=============== 功能：清除上次编译结果 ==
# Target: clean project.
clean: begin clean_list finished end

clean_list :
    $(REMOVE) $(TARGET).hex
    $(REMOVE) $(TARGET).eep
    $(REMOVE) $(TARGET).obj
    $(REMOVE) $(TARGET).cof
    $(REMOVE) $(TARGET).elf
    $(REMOVE) $(TARGET).map
    $(REMOVE) $(TARGET).obj
    $(REMOVE) $(TARGET).a90
    $(REMOVE) $(TARGET).sym
    $(REMOVE) $(TARGET).lnk
    $(REMOVE) $(TARGET).lss
    $(REMOVE) $(TARGET).cof
    $(REMOVE) $(OBJ)
    $(REMOVE) $(LST)
    $(REMOVE) $(ALLD)


#==================================================================
# Automatically generate C source code dependencies. (Code taken from the GNU make user manual.)
# Note that this will work with sh (bash) and sed that is shipped with WinAVR (see the SHELL variable defined above).
# This may not work with other shells or other seds.
#%.d: %.c
#    set -e; $(CC) -MM $(ALL_CFLAGS) $< #    | sed 's/\($*\)\.o[ :]*/\1.o $@ : /g' > $@; #    [ -s $@ ] || rm -f $@

# Remove the '-' if you want to see the dependency files generated.
#-include $(SRC:.c=.d)

# Listing of phony targets.
#.PHONY : all begin finish end sizebefore sizeafter gccversion coff clean clean_list

原文来自winavr的一个makefile的例子，我做的主要修改之处有：

1、make all 增加了cof文件的生成
2、make clean 删除了*.o等更多文件
3、其它小修改还有..但是我忘了

说明：
make clean :
   用于清除上次变编结果(如果*.h的文件改变，一定要先执行make clean,再执行make all)

make all:
   编译全部(如果只有*,c文件改变，则可以不用执行make clean)