From de32bd245c7b2d3911e7a0bbb4ebcb9c16539abd Mon Sep 17 00:00:00 2001
From: Alessandro Mauri <alemauri001@gmail.com>
Date: Thu, 23 Apr 2026 20:13:06 +0200
Subject: [PATCH] parallel compilation with redefined make rules

---
 fw/.gitignore |  2 ++
 fw/Makefile   | 31 +++++++++++++++++++++++++------
 2 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/fw/.gitignore b/fw/.gitignore
index 567b1e0..c7a9452 100644
--- a/fw/.gitignore
+++ b/fw/.gitignore
@@ -7,4 +7,6 @@
 *.map
 *.elf
 *.hex
+*.o
+.build
 compile_commands.json
diff --git a/fw/Makefile b/fw/Makefile
index b914619..5aa6221 100644
--- a/fw/Makefile
+++ b/fw/Makefile
@@ -3,24 +3,43 @@ all : build
 TARGET := main
 TARGET_MCU := CH32X035
 TARGET_MCU_PACKAGE := CH32X035F8U6
+BUILD_DIR := .build
+DISPLAY := ssd1312
 
 # include u8g2
 U8G2_DIR:=u8g2/csrc
-U8G2_SRC:=u8g2/csrc/u8x8_d_ssd1312.c $(filter-out $(U8G2_DIR)/u8x8_d_%.c, $(wildcard $(U8G2_DIR)/*.c))
-# U8G2_SRC:=u8g2/csrc/u8x8_d_ssd1306_128x32.c $(filter-out $(U8G2_DIR)/u8x8_d_%.c, $(wildcard $(U8G2_DIR)/*.c))
+U8G2_SRC:=$(U8G2_DIR)/u8x8_d_$(DISPLAY).c $(filter-out $(U8G2_DIR)/u8x8_d_%.c, \
+	$(filter-out $(U8G2_DIR)/mui%.c, $(wildcard $(U8G2_DIR)/*.c)))
 
 EXTRA_CFLAGS += -I$(U8G2_DIR)
-
-ADDITIONAL_C_FILES += $(U8G2_SRC)
-ADDITIONAL_C_FILES += lib_i2c.c
-ADDITIONAL_C_FILES += display.c
+ADDITIONAL_C_FILES += lib_i2c.c display.c
 
 include ch32fun/ch32fun/ch32fun.mk
 
 FLASH_COMMAND=$(MINICHLINK)/minichlink -C isp -w $< $(WRITE_SECTION) -b
 
+# create build directory
+$(BUILD_DIR):
+	mkdir -p $(BUILD_DIR)
+
+# build u8g2
+U8G2_OBJS := $(addprefix $(BUILD_DIR)/, $(notdir $(U8G2_SRC:.c=.o)))
+$(BUILD_DIR)/%.o : $(U8G2_DIR)/%.c | $(BUILD_DIR)
+	$(PREFIX)-gcc $(CFLAGS) -c $< -o $@
+
+# build target
+TARGET_OBJS := $(addprefix $(BUILD_DIR)/, $(filter-out ch32fun.o, $(notdir $(FILES_TO_COMPILE:.c=.o))))
+$(BUILD_DIR)/%.o : %.c | $(BUILD_DIR)
+	$(PREFIX)-gcc $(CFLAGS) -c $< -o $@
+
+# link target, the rest of the build is specified in ch32fun.mk
+$(TARGET).elf : $(FILES_TO_COMPILE) $(LINKER_SCRIPT) $(EXTRA_ELF_DEPENDENCIES) $(U8G2_OBJS) $(TARGET_OBJS) ch32fun.o
+	$(PREFIX)-gcc -o $@ $(U8G2_OBJS) $(TARGET_OBJS) ch32fun.o $(CFLAGS) $(LDFLAGS)
+
+
 flash : cv_flash
 clean : cv_clean
+	rm -f $(BUILD_DIR)/*.o *.o || true
 
 monitor :
 	picocom --imap lfcrlf /dev/ttyACM0