在之前第三章，笔者简单描述过多核通信，但是在复杂应用*享内存的合理使用我们是需要相关框架介入的。本章将围绕FreeRtos利用stream buffer(message buffer 也属于stream buffer 可以具体了解底层)实现共享内存池数据交互（部分参考sdk demo）。

 1.首先指定一个共享内存区域，指定主从核确切区域

 下面的宏，主从工程保持一致

#define APP_MESSAGE_BUFFER_EVENT_DATA                          (1U)
#define APP_MESSAGE_BUFFER_SIZE                                (128U)

#define APP_SH_MEM_PRIMARY_TO_SECONDARY_MB_OFFSET              (0x0u)
#define APP_SH_MEM_SECONDARY_TO_PRIMARY_MB_OFFSET              (0x4u)

#define APP_SH_MEM_PRIMARY_TO_SECONDARY_MB_STRUCT_OFFSET       (0x40u)
#define APP_SH_MEM_SECONDARY_TO_PRIMARY_MB_STRUCT_OFFSET       (0x80u)

#define APP_SH_MEM_PRIMARY_TO_SECONDARY_BUF_STORAGE_OFFSET     (0x200u)
#define APP_SH_MEM_SECONDARY_TO_PRIMARY_BUF_STORAGE_OFFSET     (0x800u)

#define SH_MEM_TOTAL_SIZE      (2048u)

//共享内存起始地址  前2*4Byte为描述core0 core1的基地址
#define APP_SH_MEM_BASE  (0x202c0000u)   //&Image$$RPMSG_SH_MEM$$Base

//core0 core1 基地址记录创建函数返回的句柄，这里主从要保持一致
#define xPrimaryToSecondaryMessageBuffer (*(MessageBufferHandle_t *)(APP_SH_MEM_BASE + APP_SH_MEM_PRIMARY_TO_SECONDARY_MB_OFFSET))
#define xSecondaryToPrimaryMessageBuffer (*(MessageBufferHandle_t *)(APP_SH_MEM_BASE + APP_SH_MEM_SECONDARY_TO_PRIMARY_MB_OFFSET))

//core0 core1 缓存数据描述信息
#define xPrimaryToSecondaryMessageBufferStruct (*(StaticStreamBuffer_t *)(APP_SH_MEM_BASE + APP_SH_MEM_PRIMARY_TO_SECONDARY_MB_STRUCT_OFFSET))
#define xSecondaryToPrimaryMessageBufferStruct (*(StaticStreamBuffer_t *)(APP_SH_MEM_BASE + APP_SH_MEM_SECONDARY_TO_PRIMARY_MB_STRUCT_OFFSET))

//core0 core1 数据缓存区域
#define ucPrimaryToSecondaryBufferStorage (*(uint8_t *)(APP_SH_MEM_BASE + APP_SH_MEM_PRIMARY_TO_SECONDARY_BUF_STORAGE_OFFSET))
#define ucSecondaryToPrimaryBufferStorage (*(uint8_t *)(APP_SH_MEM_BASE + APP_SH_MEM_SECONDARY_TO_PRIMARY_BUF_STORAGE_OFFSET))

 2.创建静态的stream buffer（必须静态，这样主从核才知道确切位置）

/****************************************************M7*****************************************************/    
    //m7核先clear共享区域
    (void)memset((void *)0x202c0000, 0, SH_MEM_TOTAL_SIZE);  
    /*注：必须静态创建，因为主从必须知道参数确切地址才行*/
    //返回参数：分配缓冲区句柄，实际传递的是该缓冲区描述区域地址  /* The buffer size in bytes. */ /* Statically allocated buffer storage area. */ /* Message buffer handle. */
    xPrimaryToSecondaryMessageBuffer = xMessageBufferCreateStatic(APP_MESSAGE_BUFFER_SIZE,&ucPrimaryToSecondaryBufferStorage,&xPrimaryToSecondaryMessageBufferStruct);

/****************************************************M4*****************************************************/  
    xSecondaryToPrimaryMessageBuffer = xMessageBufferCreateStatic(APP_MESSAGE_BUFFER_SIZE,&ucSecondaryToPrimaryBufferStorage,&xSecondaryToPrimaryMessageBufferStruct);

 3.内存池的读写（多核通信实现）

/****************************************************m7*****************************************************/
void xTASK_ReceiveMsg(void* pvParameters)
{
	size_t xReceivedBytes;
	
	for(;;)
	{
        //查询m4内存池参数
        xReceivedBytes = xMessageBufferReceive(xSecondaryToPrimaryMessageBuffer, (void *)&GlobData, sizeof(GlobDataTypedef), portMAX_DELAY);
		
		vTaskDelay(10);
	}
}

/****************************************************m4*****************************************************/
void xTASK_ReceiveMsg(void *pvParameters)
{
    size_t xReceivedBytes;

	while(1)
	{
        //查询m7内存池参数
		xReceivedBytes = xMessageBufferReceive(xPrimaryToSecondaryMessageBuffer, (void *)&GlobDataDefault, sizeof(GlobDataTypedef), portMAX_DELAY);
	
		//msg.cmd += 0x10; 
        GlobDataDefault.presetNow++;

        //用于测试，将从m7内核拿到的数据，m4再发给m7
		(void)xMessageBufferSend(xSecondaryToPrimaryMessageBuffer, (void *)&GlobDataDefault, sizeof(GlobDataTypedef), 0);
		
		vTaskDelay(10);
	}
}

 4.实现流程框图