#makefile variables

PRG            = count 
OBJ            = $(PRG).o
MCU_TARGET     = atmega128
OPTIMIZE       = -O0    # options are 1, 2, 3, s
OBJCOPY        = avr-objcopy
OBJDUMP        = avr-objdump
CC             = avr-gcc

#compiler and linker/loader flags
override CFLAGS        = -g -Wall $(OPTIMIZE) -mmcu=$(MCU_TARGET) 
override LDFLAGS       = -Wl,-Map,$(PRG).map

#The automatic variables make recognizes:
#   $@        file name of target, i.e., left hand side of :
#   $<        name of first prerequisite
#   $?        name of all the prerequisites that are newer than the target
#   $^, $+    Names of all the prerequisites
#

all: $(PRG).elf lst text eeprom
#######################################################################
#  The dependency for 'all" is the program.elf and three other rules.
#  The target "all" is known as a "phony target" as it is not a file 
#  but a name used to have "make" do something for you.  If no argument
#  is given to make, it processes the first rule.
#######################################################################

$(PRG).elf: $(OBJ)
	$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ 
###########################################################
#  Make understands that to make an .obj you compile a .c
#  Thus we only need to say we want a .elf from an .obj
#  $@ is make shorthand for left hand side of  ":"  (think "bulls eye")
#  $^ is make shorthand for right hand side of ":"  (all the prereqs)
###########################################################

clean: 
	rm -rf *.o $(PRG).elf *.lst *.map 
##########################################################
#  The target "clean" is another phony target that cleans
#  up all the extra files we make at each compile.
##########################################################

program: $(PRG).hex
	uisp -dprog=stk200 -dpart=atmega128 -dlpt=/dev/parport0 --erase --upload if=$(PRG).hex
##########################################################
#  Target "program" depends on the .hex file which it 
#  downloads to the target board using the parallel port.  
##########################################################

lst:  $(PRG).lst
%.lst: %.elf
	$(OBJDUMP) -h -S $< > $@
############################################################
#  The target "lst" is another phony target. Its depends 
#  on the .lst (list)  file.  The list file shows the 
#  assembly language output of the compiler intermixed
#  with the C code so it is easier to debug and follow.
#  avr-objdump ($OBJDUMP) is the avr binutil tool we us to
#  get information from the .elf file.
#
#  $@ is the file name of the target, i.e., left hand side of :
#  $< is shorthand for source file for the single dependency 
############################################################

############################################################
# Following are rules for building the .text rom images
# This is the stuff that will be put in flash. 
############################################################

#.text section holds code and read only data
text: hex bin srec

hex:  $(PRG).hex
bin:  $(PRG).bin
srec: $(PRG).srec

%.hex: %.elf
	$(OBJCOPY) -j .text -j .data -O ihex $< $@
##########################################################
#  This rule is very general in that it can take any .elf 
#  file and build the .hex file from it using avr-objcopy.
#  avr-objcopy is used to extract the downloadable portion
#  of the .elf file to build the flash image. 
##########################################################

%.srec: %.elf
	$(OBJCOPY) -j .text -j .data -O srec $< $@
##########################################################
#  Very similiar to above line except it is building 
#  Motorols S-records which are a ASCII representation
#  of the binary flash file.
##########################################################

%.bin: %.elf
	$(OBJCOPY) -j .text -j .data -O binary $< $@
##########################################################
#  Once again extracting the .bin from the .elf file. 
##########################################################

##########################################################
# Following are rules for building the .eeprom images
# This is the stuff that will be put in EEPROM.
##########################################################
eeprom: ehex ebin esrec

ehex:  $(PRG)_eeprom.hex
ebin:  $(PRG)_eeprom.bin
esrec: $(PRG)_eeprom.srec

%_eeprom.hex: %.elf
	$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O ihex $< $@
#################################################################
#This builds the EEPROM image from the .elf file for downloading.
#################################################################

%_eeprom.srec: %.elf
	$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O srec $< $@
################################################################
#This builds the S-record image from the .elf file if necessary.
################################################################

%_eeprom.bin: %.elf
	$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O binary $< $@
############################################################
#This builds a binary image from the .elf file if necessary.
############################################################