freeRTOS 平臺差異部分代碼定義（一）

protmaro.h代碼解析

類型重定義

/* Type definitions. */
#define portCHAR		char
#define portFLOAT		float
#define portDOUBLE		double
#define portLONG		long
#define portSHORT		short
#define portSTACK_TYPE	uint32_t
#define portBASE_TYPE	long

typedef portSTACK_TYPE StackType_t;
typedef long BaseType_t;
typedef unsigned long UBaseType_t;

#if( configUSE_16_BIT_TICKS == 1 )
	typedef uint16_t TickType_t;
	#define portMAX_DELAY ( TickType_t ) 0xffff
#else
	typedef uint32_t TickType_t;
	#define portMAX_DELAY ( TickType_t ) 0xffffffffUL

	/* 32-bit tick type on a 32-bit architecture, so reads of the tick count do
	not need to be guarded with a critical section. */
	#define portTICK_TYPE_IS_ATOMIC 1			
#endif

如果定義 configUSE_16_BIT_TICKS 爲 1 則表示TickType_t配置最大計數值爲16 bit。 portTICK_TYPE_IS_ATOMIC 爲1 表示32位數操作是否爲原子操作。否則需要進入臨界區才能對32位數進行操作。

構架指定

/* Architecture specifics. */
#define portSTACK_GROWTH			( -1 )		//定義堆棧生長的方向
#define portTICK_PERIOD_MS			( ( TickType_t ) 1000 / configTICK_RATE_HZ )		//調度時間片的大小
#define portBYTE_ALIGNMENT			8		//內存對齊方式，不知道爲什麼是8byte 猜測與AAPCS 要求堆棧必須8字節對齊 有關

/* Constants used with memory barrier intrinsics. */
#define portSY_FULL_READ_WRITE		( 15 )		//與內存隔離指令一起使用的條件參數

其中隔離指令的參數爲指令的option，爲確保完成所有操作必須將值設置爲0xF

定義臨界區相關的函數

/*-----------------------------------------------------------*/
//設置屏蔽中斷有消極
static portFORCE_INLINE void vPortSetBASEPRI( uint32_t ulBASEPRI )
{
	__asm
	{
		/* Barrier instructions are not used as this function is only used to
		lower the BASEPRI value. */
		msr basepri, ulBASEPRI
	}
}
/*-----------------------------------------------------------*/
//設置關閉屏蔽優先級爲0及大於0的中斷
static portFORCE_INLINE void vPortRaiseBASEPRI( void )
{
uint32_t ulNewBASEPRI = configMAX_SYSCALL_INTERRUPT_PRIORITY;

	__asm
	{
		/* Set BASEPRI to the max syscall priority to effect a critical
		section. */
		msr basepri, ulNewBASEPRI
		dsb
		isb
	}
}
/*-----------------------------------------------------------*/
//開啓所有的中斷
static portFORCE_INLINE void vPortClearBASEPRIFromISR( void )
{
	__asm
	{
		/* Set BASEPRI to 0 so no interrupts are masked.  This function is only
		used to lower the mask in an interrupt, so memory barriers are not 
		used. */
		msr basepri, #0
	}
}
/*-----------------------------------------------------------*/
//設置關閉屏蔽優先級爲0及大於0的中斷，並返回更改之前的中斷優先級
static portFORCE_INLINE uint32_t ulPortRaiseBASEPRI( void )
{
uint32_t ulReturn, ulNewBASEPRI = configMAX_SYSCALL_INTERRUPT_PRIORITY;

	__asm
	{
		/* Set BASEPRI to the max syscall priority to effect a critical
		section. */
		mrs ulReturn, basepri
		msr basepri, ulNewBASEPRI
		dsb
		isb
	}

	return ulReturn;
}
/*-----------------------------------------------------------*/
//檢查當前是否在中斷狀態，通過ipsr獲取中斷異常號來實現
static portFORCE_INLINE BaseType_t xPortIsInsideInterrupt( void )
{
uint32_t ulCurrentInterrupt;
BaseType_t xReturn;

	/* Obtain the number of the currently executing interrupt. */
	__asm
	{
		mrs ulCurrentInterrupt, ipsr
	}

	if( ulCurrentInterrupt == 0 )
	{
		xReturn = pdFALSE;
	}
	else
	{
		xReturn = pdTRUE;
	}

	return xReturn;
}