Porting RT-Thread Nano to MCUXpresso and FRDM-MCXA346 | Technical Collection

RT-Thread Nano is a lightweight hard real-time kernel. For detailed introduction, please refer to the official link:

RT-Thread Nano Introduction

After introducing the official download addresses, this article focuses on porting RT-Thread Nano to MCUXpresso IDE. The porting code can be found on the nxpic.org.cn forum. A follow-up document will also cover porting to MCUXpresso VSC (Visual Studio Code).

1. Quick Run

● Prepare a PC with the latest MCUXpresso IDE installed and an FRDM-MCXA346 development board:

● Import the code package and run the result:

2. Software Downloads

1. RT-Thread Nano source code

2. MCUXpresso SDK

3. MCUXpresso IDE

4. MCUXpresso Config Tool (optional, since the IDE already includes it)

3. Porting Steps

1. Import the MCUXpresso SDK into MCUXpresso IDE by dragging the SDK zip package into the IDE window:

2. Create a new project. Here, we use the lpuart polling example as a template. After creation, rename the project:

3. Copy the RT-Thread Nano source code into the project and add it to the build sequence:

4. Remove unnecessary files for the current platform, such as the bsp folder, the risc-v folder under libcpu, and the following under libcpu\arm: arm926, armv6, cortex-a, cortex-m0, cortex-m23, cortex-m3, cortex-m4, cortex-m7, cortex-r4.

(Keep libcpu\arm\common and cortex-m33 folders only.)

5. Exclude divsi3.S, context_iar.S, context_rvds.s, syscall_iar.S, syscall_rvds.S from the build:

4. Adapting RT-Thread Nano

1. Rename lpuart_polling.c to main.c:

2. Add rt-thread/include and rt-thread/components/finsh to the project’s include paths:

3. Copy rtconfig.h and board.c from rt-thread nano\bsp\_template into the project’s source directory. Rename board.c to rtt_board.c:

4. After compilation, the compiler reports two missing APIs that need to be added during the porting process:

5. Add “MCXA346.h”, “app.h”, and “fsl_lpuart.h” into source/board.c:

6. In void rt_hw_board_init(void) within source/board.c, add:

BOARD_InitHardware();
SysTick_Config(SystemCoreClock / RT_TICK_PER_SECOND);

7. Replace rt_os_tick_callback() with SysTick_Handler() in source/board.c:

8. Comment out TODO 2 and TODO 3.

a. TODO 2: UART debug initialization is already done in the example.

b. TODO 3: Add the following code:

9. Modify the header files in main.c:

10. Modify the core main function code in main.c:

11. Compilation will report duplicate definition of the HardFault function. Delete the auto-generated semihost_hardfault.c file:

12. Enable #define RT_USING_CONSOLE in rtconfig.h, then build and run. Remember to enable UART interrupts:

13. Upon running, the program enters Hardfault_Handler() and no UART output appears. First, fix the UART printing issue:

14. In startup/startup_mcxa346.c, hide the main call in ResetISR() and replace it with rt-thread nano entry(), as shown below，and the entry() function will call rt_hw_board_init() to initialize hardware. Rebuild and run, and now the hardfault should print messages:

15. HardFault printed messages: After several hours of debugging, the cause was identified — the linker script needed modification:

16. Right-click the project name → C/C++ Build -> Settings -> MCU Linker -> Managed Linker Script, and disable Manage Linker Script. Manual editing of the linker script is required:

17. Add the following section into frdmmcxa346_rt_thread_nano_mcux_Debug.ld, under the > PROGRAM_FLASH region:

-->
/***************RTOS
add**********************/
         /* section information for finsh shell */
         . = ALIGN(4);
         __fsymtab_start = .;
         KEEP(*(FSymTab))
         __fsymtab_end = .;
         . = ALIGN(4);
         __vsymtab_start = .;
         KEEP(*(VSymTab))
         __vsymtab_end = .;
         . = ALIGN(4);
         /* section information for utest */
         . = ALIGN(4);
         __rt_utest_tc_tab_start = .;
         KEEP(*(UtestTcTab))
         __rt_utest_tc_tab_end = .;
         /* section information for at server */
         . = ALIGN(4);
         __rtatcmdtab_start = .;
         KEEP(*(RtAtCmdTab))
         __rtatcmdtab_end = .;
         . = ALIGN(4);
         /* section information for initial. */
         . = ALIGN(4);
         __rt_init_start = .;
         KEEP(*(SORT(.rti_fn*)))
         __rt_init_end = .;
         . = ALIGN(4);
    /* section information for modules */
    . = ALIGN(4);
    __rtmsymtab_start = .;
    KEEP(*(RTMSymTab))
    __rtmsymtab_end = .;
         . = ALIGN(4);
         PROVIDE(__ctors_start__ = .);
         KEEP (*(SORT(.init_array.*)))
         KEEP (*(.init_array))
         PROVIDE(__ctors_end__ = .);
                . = ALIGN(4);

18. Compile and run, and RT-Thread Nano will now print correctly.