Raspberry Pi Pico CMake项目头文件引入及PIO I2C链接错误排查

问题概述 #

在Raspberry Pi Pico项目中添加PIO I2C功能时，编译通过但出现链接错误，提示：undefined reference to pio_i2c_read_blocking(pio_hw_t*, unsigned int, unsigned char, unsigned char*, unsigned int)

错误日志 #

[main] Building folder: Ghidorah 
[build] Starting build
[proc] Executing command: /usr/bin/cmake --build /home/varun/Projects/Ghidorah/build --config Debug --target all -j 10 --
[build] [  5%] Performing build step for 'PioasmBuild'
[build] [  5%] Built target bs2_default
[build] [  5%] Performing build step for 'ELF2UF2Build'
[build] [ 16%] Built target FreeRTOS-Kernel
[build] [ 18%] Built target bs2_default_padded_checksummed_asm
[build] [100%] Built target elf2uf2
[build] [100%] Built target pioasm
[build] [ 20%] No install step for 'ELF2UF2Build'
[build] [ 20%] No install step for 'PioasmBuild'
[build] [ 23%] Completed 'PioasmBuild'
[build] [ 23%] Completed 'ELF2UF2Build'
[build] [ 32%] Built target PioasmBuild
[build] [ 34%] Built target ELF2UF2Build
[build] [ 36%] Built target Ghidorah_i2c_pio_h
[build] [ 37%] Linking CXX executable Ghidorah.elf
[build] /usr/lib/gcc/arm-none-eabi/10.3.1/../../../arm-none-eabi/bin/ld: CMakeFiles/Ghidorah.dir/Sensors/mpu6050/source/mpu6050.cpp.obj: in function `scan()':
[build] /home/varun/Projects/Ghidorah/Sensors/mpu6050/source/mpu6050.cpp:32: undefined reference to `pio_i2c_read_blocking(pio_hw_t*, unsigned int, unsigned char, unsigned char*, unsigned int)'
[build] collect2: error: ld returned 1 exit status
[build] gmake[2]: *** [CMakeFiles/Ghidorah.dir/build.make:936: Ghidorah.elf] Error 1
[build] gmake[1]: *** [CMakeFiles/Makefile2:1496: CMakeFiles/Ghidorah.dir/all] Error 2
[build] gmake: *** [Makefile:91: all] Error 2
[proc] The command: /usr/bin/cmake --build /home/varun/Projects/Ghidorah/build --config Debug --target all -j 10 -- exited with code: 2
[build] Build finished with exit code 2

当前CMakeLists.txt内容 #

# Generated Cmake Pico project file

cmake_minimum_required(VERSION 3.13)

set(CMAKE_C_STANDARD 11)
set(CMAKE_CXX_STANDARD 17)

# Initialise pico_sdk from installed location
# (note this can come from environment, CMake cache etc)
set(PICO_SDK_PATH "/home/varun/Dev-Tools/pico/pico-sdk")

set(PICO_BOARD pico CACHE STRING "Board type")

# Pull in Raspberry Pi Pico SDK (must be before project)
include(pico_sdk_import.cmake)

if (PICO_SDK_VERSION_STRING VERSION_LESS "1.4.0")
  message(FATAL_ERROR "Raspberry Pi Pico SDK version 1.4.0 (or later) required. Your version is ${PICO_SDK_VERSION_STRING}")
endif()

add_compile_options(-Wall
        -Wno-format          # int != int32_t as far as the compiler is concerned because gcc has int32_t as long int
        -Wno-unused-function # we have some for the docs that aren't called
        -Wno-maybe-uninitialized
        -fpermissive
        )

project(Ghidorah C CXX ASM)

# Initialise the Raspberry Pi Pico SDK
pico_sdk_init()

# Add executable. Default name is the project name, version 0.1

add_executable(Ghidorah Ghidorah.cpp 
        Sensors/mpu6050/source/mpu6050.cpp
        Sensors/mpu9250/source/mpu9250.cpp
        Sensors/adxl345/source/adxl345.cpp
        Sensors/lsm303dhlc/source/lsm303dhlc.cpp
        pio/pio_i2c.c)

pico_generate_pio_header(Ghidorah ${CMAKE_CURRENT_SOURCE_DIR}/pio/i2c.pio)

pico_set_program_name(Ghidorah "Ghidorah")
pico_set_program_version(Ghidorah "0.1")

pico_enable_stdio_uart(Ghidorah 1)
pico_enable_stdio_usb(Ghidorah 0)

# Add the standard library to the build
target_link_libraries(Ghidorah
        pico_stdlib
        pico_multicore)

# Add the standard include files to the build
target_include_directories(Ghidorah PRIVATE
        ${CMAKE_CURRENT_LIST_DIR}
        ${CMAKE_CURRENT_LIST_DIR}/.. # for our common lwipopts or any other standard includes, if required
        ${CMAKE_CURRENT_SOURCE_DIR}/

        #       SENSOR Sources
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors        
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/mpu6050/
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/mpu6050/include
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/mpu9250/
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/mpu9250/include
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/adxl345/
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/adxl345/include
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/lsm303dhlc/
        ${CMAKE_CURRENT_SOURCE_DIR}/Sensors/lsm303dhlc/include
        
        #       PIO Sources
        ${CMAKE_CURRENT_SOURCE_DIR}/pio
        ${CMAKE_CURRENT_SOURCE_DIR}/pio/)

add_library(FreeRTOS-Kernel STATIC
        FreeRTOS-Kernel/event_groups.c
        FreeRTOS-Kernel/list.c
        FreeRTOS-Kernel/queue.c
        FreeRTOS-Kernel/stream_buffer.c
        FreeRTOS-Kernel/tasks.c
        FreeRTOS-Kernel/timers.c
        FreeRTOS-Kernel/portable/GCC/ARM_CM0/port.c
        FreeRTOS-Kernel/portable/Common/mpu_wrappers.c
        FreeRTOS-Kernel/portable/MemMang/heap_3.c)

target_include_directories(FreeRTOS-Kernel PUBLIC
        FreeRTOS-Kernel/
        FreeRTOS-Kernel/include/
        FreeRTOS-Kernel/portable/Common/
        FreeRTOS-Kernel/portable/GCC/
        FreeRTOS-Kernel/portable/GCC/ARM_CM0/
        FreeRTOS-Kernel/portable/MemMang/)

# Add any user requested libraries
target_link_libraries(Ghidorah
        hardware_dma
        hardware_gpio
        hardware_pio
        FreeRTOS-Kernel)

pico_add_extra_outputs(Ghidorah)

解决方案 #

链接错误的核心原因是C++代码调用C语言实现的函数时，未声明C语言链接约定，导致编译器按C++名字修饰规则查找函数，无法匹配C语言编译的函数符号。

具体修复步骤： #

1. 修改PIO I2C头文件：在声明pio_i2c_read_blocking的头文件（如pio_i2c.h）中，用extern "C"包裹所有函数声明，示例如下：

#ifdef __cplusplus
extern "C" {
#endif

// 所有PIO I2C相关函数声明
void pio_i2c_read_blocking(pio_hw_t* pio, uint sm, uint8_t addr, uint8_t* dst, size_t len);
// 其他函数声明...

#ifdef __cplusplus
}
#endif

2. 确认源文件编译状态：pio_i2c.c是C语言文件，CMake会自动按C规则编译，且你的配置中已将其加入add_executable，这部分无需修改。

3. 清理重建项目：删除build目录，重新运行CMake配置和编译，确保修改生效。

额外检查点： #

• 确认pio_i2c.c中pio_i2c_read_blocking的函数签名与头文件声明完全一致（参数类型、数量、返回值类型均需匹配）。
• 若使用Pico SDK示例中的PIO I2C代码，需确保头文件已包含上述extern "C"声明。

内容的提问来源于stack exchange，提问作者varun koganti