【国民技术N32项目移植】N32WB452芯片移植--3、移植腾讯TinyOS

3、移植RTOS的三个要点

3.1 线程的栈信息初始化

由于N32WB452使用的是Cortex-M4内核，而Cortex-M3和Cortex-M4都基于ARMv7-M架构。腾讯TinyOS的ARMv7-M架构支持已经很完善了。这里我们不需要自己去写对应的代码，只需要使用系统里自带的源码即可。

RTOS想从主程序切换到线程上，或者进行线程间的切换，就需要线程的栈信息。然后在准备线程的相关信息时，线程的栈保存是很关键的，如果sp地址没指向正确的地址，就跑飞了。

如果是自己从零开始写，就需要注意port.S文件里，保存寄存器时的顺序，和这个初始化函数里定义的顺序是否一致。

源码的文件路径，arch/arm/arm-v7m/common/tos_cpu.c

__KNL__k_stack_t*cpu_task_stk_init(void*entry,void*arg,void*exit,k_stack_t*stk_base,size_tstk_size){cpu_data_t*sp; sp = (cpu_data_t*)&stk_base[stk_size]; sp = (cpu_data_t*)((cpu_addr_t)sp &0xFFFFFFF8);#ifTOS_CFG_TASK_STACK_DRAUGHT_DEPTH_DETACT_EN > 0uuint8_t*slot = (uint8_t*)&stk_base[0];for(; slot < (uint8_t*)sp; ++slot) { *slot =0xCC; }#endif/* auto-saved on exception(pendSV) by hardware */*--sp = (cpu_data_t)0x01000000u;/* xPSR */*--sp = (cpu_data_t)entry;/* entry */*--sp = (cpu_data_t)exit;/* R14 (LR) */*--sp = (cpu_data_t)0x12121212u;/* R12 */*--sp = (cpu_data_t)0x03030303u;/* R3 */*--sp = (cpu_data_t)0x02020202u;/* R2 */*--sp = (cpu_data_t)0x01010101u;/* R1 */*--sp = (cpu_data_t)arg;/* R0: arg *//* Remaining registers saved on process stack *//* EXC_RETURN = 0xFFFFFFFDL Initial state: Thread mode + non-floating-point state + PSP 31 - 28 : EXC_RETURN flag, 0xF 27 - 5 : reserved, 0xFFFFFE 4 : 1, basic stack frame; 0, extended stack frame 3 : 1, return to Thread mode; 0, return to Handler mode 2 : 1, return to PSP; 0, return to MSP 1 : reserved, 0 0 : reserved, 1 */#ifdefined (TOS_CFG_CPU_ARM_FPU_EN) && (TOS_CFG_CPU_ARM_FPU_EN == 1U)*--sp = (cpu_data_t)0xFFFFFFFDL;#endif*--sp = (cpu_data_t)0x11111111u;/* R11 */*--sp = (cpu_data_t)0x10101010u;/* R10 */*--sp = (cpu_data_t)0x09090909u;/* R9 */*--sp = (cpu_data_t)0x08080808u;/* R8 */*--sp = (cpu_data_t)0x07070707u;/* R7 */*--sp = (cpu_data_t)0x06060606u;/* R6 */*--sp = (cpu_data_t)0x05050505u;/* R5 */*--sp = (cpu_data_t)0x04040404u;/* R4 */return(k_stack_t*)sp; }

如果确定这个线程栈信息是正确初始化了，那接下来就可以看线程切换时，保存和恢复现场的相关代码了。

3.2 现场保存和恢复相关功能

在初始化了线程的相关内容后，就可以准备开始第一次的线程调度了。然后线程调度的相关汇编代码是在arch/arm/arm-v7m/cortex-m4/gcc/port_s.S这个文件里。

相关的代码也是不需要我们写的，除了下面展示的现场保存和恢复部分的汇编代码以外，开关中断，初次调度线程，唤起调度中断等等内容都是实现好了的。没必要自己去写，有兴趣研究的，可以用一块能运行TinyOS的开发板，在对应的功能上打断点，然后再查看运行前后的mcu寄存器值去学习和了解。

.thumb_func .typePendSV_Handler, %function PendSV_Handler: CPSID I MRS R0, PSP _context_save:@ R0-R3, R12, LR, PC, xPSR is saved automatically here#if (defined(__VFP_FP__) && !defined(__SOFTFP__))@ is it extended frame?TST LR,#0x10IT EQ VSTMDBEQ R0!, {S16 - S31}@ S0 - S16, FPSCR saved automatically here@ save EXC_RETURNSTMFD R0!, {LR}#endif@ save remaining regs r4 -11on process stackSTMFD R0!, {R4 - R11}@ k_curr_task->sp = PSP;MOVW R5,#:lower16:k_curr_taskMOVT R5,#:upper16:k_curr_taskLDR R6, [R5]@ R0 is SP of process being switched outSTR R0, [R6] _context_restore:@ k_curr_task = k_next_task;MOVW R1,#:lower16:k_next_taskMOVT R1,#:upper16:k_next_taskLDR R2, [R1] STR R2, [R5]@ R0 = k_next_task->spLDR R0, [R2]@ restore R4 - R11LDMFD R0!, {R4 - R11}#if (defined(__VFP_FP__) && !defined(__SOFTFP__))@ restore EXC_RETURNLDMFD R0!, {LR}@ is it extended frame?TST LR,#0x10IT EQ VLDMIAEQ R0!, {S16 - S31}#endif@ Load PSP with new process SPMSR PSP, R0 CPSIE I@ R0-R3, R12, LR, PC, xPSR restored automatically here@ S0 - S16, FPSCR restored automatically here if FPCA =1BX LR .end

3.3 系统心跳

在platform/vendor_bsp/st/CMSIS/Core/Include/core_cm4.h文件里，已经实现了通用的系统心跳配置函数，这个也是不需要我们去写的。配置系统心跳的相关内容也不需要我们管，在TinyOS启动内核时会初始化系统心跳。

/** \brief System Tick Configuration \details Initializes the System Timerandits interrupt,andstarts the System Tick Timer. Counterisinfree running mode to generate periodic interrupts. \param [in] ticks Numberofticks between two interrupts. \return0Functionsucceeded.\return1Functionfailed.\note When the variable __Vendor_SysTickConfigisset to1,thenthefunctionSysTick_Configisnotincluded.Inthiscase, the file device.h must contain a vendor-specific implementationofthisfunction. */ __STATIC_INLINE uint32_t SysTick_Config(uint32_t ticks) {if((ticks -1UL) > SysTick_LOAD_RELOAD_Msk) {return(1UL); /* Reload value impossible */ } SysTick->LOAD = (uint32_t)(ticks -1UL); /* set reload register */ NVIC_SetPriority (SysTick_IRQn, (1UL << __NVIC_PRIO_BITS) -1UL); /* set PriorityforSystick Interrupt */ SysTick->VAL =0UL; /* Load the SysTick Counter Value */ SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_TICKINT_Msk | SysTick_CTRL_ENABLE_Msk; /* Enable SysTick IRQandSysTick Timer */return(0UL); /*Functionsuccessful*/ }

我们只需要在bsp里把SysTick_Handler的实现函数修改一下就可以了。

/** * @brief This function handles System tick timer. */voidSysTick_Handler(void) {if(tos_knl_is_running()) {tos_knl_irq_enter();tos_tick_handler();tos_knl_irq_leave(); } }

最后，我们在main.c文件里创建两个调试线程

#defineAPPLICATION_TASK_STK_SIZE 1024k_task_tapplication_task; __aligned(4)uint8_tapplication_task_stk[APPLICATION_TASK_STK_SIZE];k_task_tapplication_task1; __aligned(4)uint8_tapplication_task1_stk[APPLICATION_TASK_STK_SIZE];voidapplication_entry(void*arg){while(1) {tos_task_delay(2500);printf("task1 running!\r\n"); }; }voidapplication_entry2(void*arg){while(1) {tos_task_delay(1200);printf("task2 running!\r\n"); }; }

然后在main函数里创建这两个线程，并开启调度就可以啦

/********************************************************************* *@fn main** @brief Main program. **@return none*/ int main(void) { bsp_init(); // 初始化debug串口和板级外设 tos_knl_init(); // 初始化TencentOS tiny内核 printf("TinyOS demo!\r\n"); // 创建一个优先级为5的任务 tos_task_create(&application_task, "task_prio5", application_entry, NULL, 4, application_task_stk, APPLICATION_TASK_STK_SIZE, 0); // 创建一个优先级为5的任务 tos_task_create(&application_task1, "task_prio5", application_entry2, NULL, 4, application_task1_stk, APPLICATION_TASK_STK_SIZE, 0); // 开始内核调度，线程中不允许有睡死代码。 tos_knl_start(); while (1) { } }

然后就编译、烧录，最后看到串口欢快的跳起线程里的输出内容啦。