C++ Setup in STM32

1. CubeMX Configuration 

There is nothing special to do in CubeMX for C++ setup. You can follow the same steps as in C setup. First we see makefile then cmake. Also make a pin GPIO_Output for LED. For example, in bluepill (STM32F103C8), pin PC13 is connected to LED.

Note

You can generate code using toolchain as Makefile, then later migrate to CMake, and vice versa.

2. Update Makefile to Compile C++ Code 

Note

Add the block to Makefile which have green border at left.

2.1. Add `CXX_SOURCES` after `C_SOURCES`:

# C sources
C_SOURCES =  \
Core/Src/main.c \
Core/Src/gpio.c \
Core/Src/stm32f4xx_it.c \
Core/Src/stm32f4xx_hal_msp.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_rcc.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_rcc_ex.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_flash.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_flash_ex.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_flash_ramfunc.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_gpio.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_dma_ex.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_dma.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_pwr.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_pwr_ex.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_cortex.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_exti.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_tim.c \
Drivers/STM32F4xx_HAL_Driver/Src/stm32f4xx_hal_tim_ex.c \
Core/Src/system_stm32f4xx.c \
Core/Src/sysmem.c \
Core/Src/syscalls.c

# CXX sources
CXX_SOURCES =

# ASM sources
ASM_SOURCES =  \
startup_stm32f407xx.s

2.2. Add Compiler for C++:

ifdef GCC_PATH
CC = $(GCC_PATH)/$(PREFIX)gcc
AS = $(GCC_PATH)/$(PREFIX)gcc -x assembler-with-cpp
CP = $(GCC_PATH)/$(PREFIX)objcopy
SZ = $(GCC_PATH)/$(PREFIX)size

CXX = $(GCC_PATH)/$(PREFIX)g++

else
CC = $(PREFIX)gcc
AS = $(PREFIX)gcc -x assembler-with-cpp
CP = $(PREFIX)objcopy
SZ = $(PREFIX)size

CXX = $(PREFIX)g++

else
HEX = $(CP) -O ihex
BIN = $(CP) -O binary -S

2.3. Add `CXX_INCLUDE` after `C_INCLUDES`:

# C includes
C_INCLUDES =  \
-ICore/Inc \
-IDrivers/STM32F4xx_HAL_Driver/Inc \
-IDrivers/STM32F4xx_HAL_Driver/Inc/Legacy \
-IDrivers/CMSIS/Device/ST/STM32F4xx/Include \
-IDrivers/CMSIS/Include

# CXX Includes
CXX_INCLUDES = \
$(C_INCLUDES)

2.4. Add CXXFLAGS:

# compile gcc flags
ASFLAGS = $(MCU) $(AS_DEFS) $(AS_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections

CFLAGS += $(MCU) $(C_DEFS) $(C_INCLUDES) $(OPT) -Wall -fdata-sections -ffunction-sections

ifeq ($(DEBUG), 1)
CFLAGS += -g -gdwarf-2
endif


# Generate dependency information
CFLAGS += -MMD -MP -MF"$(@:%.o=%.d)"

CXXFLAGS = $(CFLAGS) $(CXX_INCLUDES)

2.5. Add list of objects for CXX:

# list of objects
OBJECTS = $(addprefix $(BUILD_DIR)/,$(notdir $(C_SOURCES:.c=.o)))
vpath %.c $(sort $(dir $(C_SOURCES)))
# list of ASM program objects
OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(ASM_SOURCES:.s=.o)))
vpath %.s $(sort $(dir $(ASM_SOURCES)))
OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(ASMM_SOURCES:.S=.o)))
vpath %.S $(sort $(dir $(ASMM_SOURCES)))

# list of CXX program objects
OBJECTS += $(addprefix $(BUILD_DIR)/,$(notdir $(CXX_SOURCES:.cpp=.o)))
vpath %.cpp $(sort $(dir $(CXX_SOURCES)))

2.6. Add to build cpp files:

$(BUILD_DIR)/%.o: %.c Makefile | $(BUILD_DIR) 
	$(CC) -c $(CFLAGS) -Wa,-a,-ad,-alms=$(BUILD_DIR)/$(notdir $(<:.c=.lst)) $< -o $@

$(BUILD_DIR)/%.o: %.s Makefile | $(BUILD_DIR)
	$(AS) -c $(CFLAGS) $< -o $@
$(BUILD_DIR)/%.o: %.S Makefile | $(BUILD_DIR)
	$(AS) -c $(CFLAGS) $< -o $@

$(BUILD_DIR)/%.o: %.cpp Makefile | $(BUILD_DIR)
	$(CXX) -c $(CXXFLAGS) $< -o $@

$(BUILD_DIR)/$(TARGET).elf: $(OBJECTS) Makefile
	$(CC) $(OBJECTS) $(LDFLAGS) -o $@
	$(SZ) $@

$(BUILD_DIR)/%.hex: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
	$(HEX) $< $@
	
$(BUILD_DIR)/%.bin: $(BUILD_DIR)/%.elf | $(BUILD_DIR)
	$(BIN) $< $@	
	
$(BUILD_DIR):
	mkdir $@	

Makefile is ready to compile C++ file. We need to add .cpp file to CXX_sources. Verify makefile syntax.

make -j

It should not give any warning or error.

3. Create new cplusplus files to project 

Navigate to Core > Inc, create a new file app.h and copy the following code.

#ifndef __APP_H
#define __APP_H

#ifdef __cplusplus
extern "C" {
#endif

void setup();

void loop();

#ifdef __cplusplus
}
#endif

#endif // __APP_H

Navigate to Core > Src ``, create a new file ``app.cpp and copy the following code.

#include "app.h"

#include "stm32f1xx_hal.h"

void setup()
{
    // executes once
}

void loop()
{
    // executes continuesly
    HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_13);
    HAL_Delay(100);
}

Open main.c file and include app.h.

/* USER CODE BEGIN Includes */
#include "app.h"
/* USER CODE END Includes */

Call setup() and loop() function in main().

/* USER CODE BEGIN 2 */
setup();
/* USER CODE END 2 */

/* Infinite loop */
/* USER CODE BEGIN WHILE */
while (1)
{
  loop();
  /* USER CODE END WHILE */
  /* USER CODE BEGIN 3 */
}
/* USER CODE END 3 */

4. Add `app.cpp` to Makefile.

# CXX sources
CXX_SOURCES =  \
Core/Src/app.cpp

Compile and flash the code. The LED should blink.

5. Migrate to CMake 

Open STM32CubeMX, go to Project Manager > Project and select Toolchain/IDE as CMake. Generate code. CMakeLists.txt will be generated in the project folder. You donot need to delete Makefile. You can use both Makefile and CMake.

6. Update CMakeLists.txt 

6.1. Set C++ standard:

# Setup compiler settings
set(CMAKE_C_STANDARD 11)
set(CMAKE_C_STANDARD_REQUIRED ON)
set(CMAKE_C_EXTENSIONS ON)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_CXX_EXTENSIONS ON)

6.2. Enabe CXX support:

Enabe CXX support by editing the line enable_language(C ASM).

enable_language(CXX C ASM)

6.3. Add CXX sources:

# Add sources to executable
target_sources(${CMAKE_PROJECT_NAME} PRIVATE
    # Add user sources here
    ${CMAKE_SOURCE_DIR}/Core/Src/app.cpp
)

Compile and flash the code. The LED should blink.