CROSS_COMPILE ?= avr-

TARGET_FILE ?= avr.elf

MCU = attiny85
DUDE_MCU = t85

C_FLAGS += -Wall -Werror
C_FLAGS += -Os
C_FLAGS += -mmcu=$(MCU)
C_FLAGS += -ffunction-sections
C_FLAGS += -fdata-sections
C_FLAGS += -std=c11
C_FLAGS += -pedantic
C_FLAGS += -pedantic-errors
C_FLAGS += -Iinclude

DUDE_FLAGS = -p $(DUDE_MCU)
DUDE_FLAGS += -P /dev/spidev0.0
DUDE_FLAGS += -c linuxspi
DUDE_FLAGS += -b 10000

CC = $(CROSS_COMPILE)gcc
AS = $(CROSS_COMPILE)as
LD = $(CROSS_COMPILE)ld
OBJCOPY = $(CROSS_COMPILE)objcopy
SIZE = $(CROSS_COMPILE)size
AVRDUDE = avrdude

OBJ_DIR := objs
BIN_DIR := bin
SRC_DIR := src

C_SRCS = $(wildcard $(SRC_DIR)/*.c)
C_OBJS = $(patsubst %.c,$(OBJ_DIR)/%.o,$(notdir $(C_SRCS)))

OBJS = $(C_OBJS)
TARGET = $(BIN_DIR)/$(TARGET_FILE)

.PHONY: all
all: $(TARGET)

$(TARGET): $(OBJS) Makefile
	@mkdir -p $(BIN_DIR)
	$(CC) $(LD_FLAGS) $(LINKER_SCRIPT) $(OBJS) $(LD_LIBS) -o $@ -Wl,-Map=$(BIN_DIR)/$(notdir $(basename $@)).map
	$(OBJCOPY) -O ihex $(TARGET) $(subst .elf,.hex,$(TARGET))
	$(SIZE) $@

$(OBJ_DIR)/%.o: $(SRC_DIR)/%.c
	@mkdir -p $(dir $@)
	@$(call makedep,$<,$@,$(patsubst %.c,%.d,$(OBJ_DIR)/$(notdir $<)),$(C_FLAGS))
	$(CC) -c $(C_FLAGS) $(CCFLAGS) -o $@ $<

.PHONY: clean
clean:
	rm -rf \
	$(OBJS) \
	$(patsubst %.o,%.d,$(OBJS)) \
	$(TARGET) \
	$(subst .elf,.map,$(TARGET)) \
	$(subst .elf,.hex,$(TARGET))

.PHONY: flash
flash: $(TARGET)
	gpio 22 off
	$(AVRDUDE) $(DUDE_FLAGS) -U flash:w:$(subst .elf,.hex,$(TARGET))
	gpio 22 on

define makedep
	$(CC) -MM -MF $3 -MP -MT $2 $4 $1
endef

ifneq ($(MAKECMDGOALS),clean)
-include $($(subst .o,.d,$(OBJS))
endif