Code:

DEVICE  = atmega8
F_CPU   = 12000000   # in Hz
FUSE_L  = 0x1f
FUSE_H  = 0xc1
AVRDUDE = avrdude -c usbasp -p $(DEVICE) # edit this line for your programmer

CFLAGS  = -Iusbdrv -I. -DDEBUG_LEVEL=0
OBJECTS = usbdrv/usbdrv.o usbdrv/usbdrvasm.o usbdrv/oddebug.o adc.o main.o

COMPILE = avr-gcc -Wall -Os -DF_CPU=$(F_CPU) $(CFLAGS) -mmcu=$(DEVICE)

##############################################################################
# Fuse values for particular devices
##############################################################################
# If your device is not listed here, go to
# http://palmavr.sourceforge.net/cgi-bin/fc.cgi
# and choose options for external crystal clock and no clock divider
#
################################## ATMega8 ##################################
# ATMega8 FUSE_L (Fuse low byte):
# 0x9f = 1 0 0 1   1 1 1 1
#        ^ ^ \ /   \--+--/
#        | |  |       +------- CKSEL 3..0 (external >8M crystal)
#        | |  +--------------- SUT 1..0 (crystal osc, BOD enabled)
#        | +------------------ BODEN (BrownOut Detector enabled)
#        +-------------------- BODLEVEL (2.7V)
# ATMega8 FUSE_H (Fuse high byte):
# 0xc9 = 1 1 0 0   1 0 0 1 <-- BOOTRST (boot reset vector at 0x0000)
#        ^ ^ ^ ^   ^ ^ ^------ BOOTSZ0
#        | | | |   | +-------- BOOTSZ1
#        | | | |   + --------- EESAVE (don't preserve EEPROM over chip erase)
#        | | | +-------------- CKOPT (full output swing)
#        | | +---------------- SPIEN (allow serial programming)
#        | +------------------ WDTON (WDT not always on)
#        +-------------------- RSTDISBL (reset pin is enabled)
#
############################## ATMega48/88/168 ##############################
# ATMega*8 FUSE_L (Fuse low byte):
# 0xdf = 1 1 0 1   1 1 1 1
#        ^ ^ \ /   \--+--/
#        | |  |       +------- CKSEL 3..0 (external >8M crystal)
#        | |  +--------------- SUT 1..0 (crystal osc, BOD enabled)
#        | +------------------ CKOUT (if 0: Clock output enabled)
#        +-------------------- CKDIV8 (if 0: divide by 8)
# ATMega*8 FUSE_H (Fuse high byte):
# 0xde = 1 1 0 1   1 1 1 0
#        ^ ^ ^ ^   ^ \-+-/
#        | | | |   |   +------ BODLEVEL 0..2 (110 = 1.8 V)
#        | | | |   + --------- EESAVE (preserve EEPROM over chip erase)
#        | | | +-------------- WDTON (if 0: watchdog always on)
#        | | +---------------- SPIEN (allow serial programming)
#        | +------------------ DWEN (debug wire enable)
#        +-------------------- RSTDISBL (reset pin is enabled)
#
############################## ATTiny25/45/85 ###############################
# ATMega*5 FUSE_L (Fuse low byte):
# 0xef = 1 1 1 0   1 1 1 1
#        ^ ^ \+/   \--+--/
#        | |  |       +------- CKSEL 3..0 (clock selection -> crystal @ 12 MHz)
#        | |  +--------------- SUT 1..0 (BOD enabled, fast rising power)
#        | +------------------ CKOUT (clock output on CKOUT pin -> disabled)
#        +-------------------- CKDIV8 (divide clock by 8 -> don't divide)
# ATMega*5 FUSE_H (Fuse high byte):
# 0xdd = 1 1 0 1   1 1 0 1
#        ^ ^ ^ ^   ^ \-+-/ 
#        | | | |   |   +------ BODLEVEL 2..0 (brownout trigger level -> 2.7V)
#        | | | |   +---------- EESAVE (preserve EEPROM on Chip Erase -> not preserved)
#        | | | +-------------- WDTON (watchdog timer always on -> disable)
#        | | +---------------- SPIEN (enable serial programming -> enabled)
#        | +------------------ DWEN (debug wire enable)
#        +-------------------- RSTDISBL (disable external reset -> enabled)
#
################################ ATTiny2313 #################################
# ATTiny2313 FUSE_L (Fuse low byte):
# 0xef = 1 1 1 0   1 1 1 1
#        ^ ^ \+/   \--+--/
#        | |  |       +------- CKSEL 3..0 (clock selection -> crystal @ 12 MHz)
#        | |  +--------------- SUT 1..0 (BOD enabled, fast rising power)
#        | +------------------ CKOUT (clock output on CKOUT pin -> disabled)
#        +-------------------- CKDIV8 (divide clock by 8 -> don't divide)
# ATTiny2313 FUSE_H (Fuse high byte):
# 0xdb = 1 1 0 1   1 0 1 1
#        ^ ^ ^ ^   \-+-/ ^
#        | | | |     |   +---- RSTDISBL (disable external reset -> enabled)
#        | | | |     +-------- BODLEVEL 2..0 (brownout trigger level -> 2.7V)
#        | | | +-------------- WDTON (watchdog timer always on -> disable)
#        | | +---------------- SPIEN (enable serial programming -> enabled)
#        | +------------------ EESAVE (preserve EEPROM on Chip Erase -> not preserved)
#        +-------------------- DWEN (debug wire enable)


# symbolic targets:
help:
   @echo "This Makefile has no default rule. Use one of the following:"
   @echo "make hex ....... to build main.hex"
   @echo "make program ... to flash fuses and firmware"
   @echo "make fuse ...... to flash the fuses"
   @echo "make flash ..... to flash the firmware (use this on metaboard)"
   @echo "make clean ..... to delete objects and hex file"

hex: main.hex

program: flash fuse

# rule for programming fuse bits:
fuse:
   @[ "$(FUSE_H)" != "" -a "$(FUSE_L)" != "" ] || \
      { echo "*** Edit Makefile and choose values for FUSE_L and FUSE_H!"; exit 1; }
   $(AVRDUDE) -U hfuse:w:$(FUSE_H):m -U lfuse:w:$(FUSE_L):m

# rule for uploading firmware:
flash: main.hex
   $(AVRDUDE) -U flash:w:main.hex:i

# rule for deleting dependent files (those which can be built by Make):
clean:
   rm -f main.hex main.lst main.obj main.cof main.list main.map main.eep.hex main.elf *.o usbdrv/*.o main.s usbdrv/oddebug.s usbdrv/usbdrv.s

# Generic rule for compiling C files:
.c.o:
   $(COMPILE) -c $< -o $@

# Generic rule for assembling Assembler source files:
.S.o:
   $(COMPILE) -x assembler-with-cpp -c $< -o $@
# "-x assembler-with-cpp" should not be necessary since this is the default
# file type for the .S (with capital S) extension. However, upper case
# characters are not always preserved on Windows. To ensure WinAVR
# compatibility define the file type manually.

# Generic rule for compiling C to assembler, used for debugging only.
.c.s:
   $(COMPILE) -S $< -o $@

# file targets:

# Since we don't want to ship the driver multipe times, we copy it into this project:
#usbdrv:
#   cp -r ../../../usbdrv .

main.elf: $(OBJECTS)   # usbdrv dependency only needed because we copy it
   $(COMPILE) -o main.elf $(OBJECTS)

main.hex: main.elf
   rm -f main.hex main.eep.hex
   avr-objcopy -j .text -j .data -O ihex main.elf main.hex
   avr-size main.hex

# debugging targets:

disasm:   main.elf
   avr-objdump -d main.elf

cpp:
   $(COMPILE) -E main.c adc.c adc.h