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[RTOS Stream Buffer API]
StaticStreamBuffer_t *pxStaticStreamBuffer );
configSUPPORT_STATIC_ALLOCATION must be set to 1 in FreeRTOSConfig.h for xStreamBufferCreateStatic() to be available.
Stream buffer functionality is enabled by including the FreeRTOS/source/stream_buffer.c source file in the build.
xBufferSizeBytes The size, in bytes, of the buffer pointed to by the pucStreamBufferStorageArea parameter. xTriggerLevelBytes The number of bytes that must be in the stream buffer before a task that is blocked on the stream buffer to wait for data is moved out of the blocked state. For example, if a task is blocked on a read of an empty stream buffer that has a trigger level of 1 then the task will be unblocked when a single byte is written to the buffer or the task’s block time expires. As another example, if a task is blocked on a read of an empty stream buffer that has a trigger level of 10 then the task will not be unblocked until the stream buffer contains at least 10 bytes or the task’s block time expires. If a reading task’s block time expires before the trigger level is reached then the task will still receive however many bytes are actually available. Setting a trigger level of 0 will result in a trigger level of 1 being used. It is not valid to specify a trigger level that is greater than the buffer size. pucStreamBufferStorageArea Must point to a uint8_t array that is at least xBufferSizeBytes + 1 big. This is the array to which streams are copied when they are written to the stream buffer. pxStaticStreamBuffer Must point to a variable of type StaticStreamBuffer_t, which will be used to hold the stream buffer’s data structure.
- If the stream buffer is created successfully then a handle to the created stream buffer is returned. If either pucStreamBufferStorageArea or pxStaticstreamBuffer are NULL then NULL is returned.
/* Used to dimension the array used to hold the streams. The available space
will actually be one less than this, so 999. */
#define STORAGE_SIZE_BYTES 1000
/* Defines the memory that will actually hold the streams within the stream
static uint8_t ucBufferStorage[ STORAGE_SIZE_BYTES ];
/* The variable used to hold the stream buffer structure. */
void MyFunction( void )
const size_t xTriggerLevel = 1;
xStreamBuffer = xStreamBufferCreateStatic( sizeof( ucBufferStorage ),
/* As neither the pucStreamBufferStorageArea or pxStaticStreamBuffer
parameters were NULL, xStreamBuffer will not be NULL, and can be used to
reference the created stream buffer in other stream buffer API calls. */
/* Other code that uses the stream buffer can go here. */