780 lines
35 KiB
C
780 lines
35 KiB
C
/*
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* FreeRTOS Kernel V10.0.1
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* Copyright (C) 2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy of
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* this software and associated documentation files (the "Software"), to deal in
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* the Software without restriction, including without limitation the rights to
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* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
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* the Software, and to permit persons to whom the Software is furnished to do so,
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* subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in all
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* copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
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* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
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* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
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* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* http://www.FreeRTOS.org
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* http://aws.amazon.com/freertos
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*
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* 1 tab == 4 spaces!
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*/
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/*
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* Message buffers build functionality on top of FreeRTOS stream buffers.
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* Whereas stream buffers are used to send a continuous stream of data from one
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* task or interrupt to another, message buffers are used to send variable
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* length discrete messages from one task or interrupt to another. Their
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* implementation is light weight, making them particularly suited for interrupt
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* to task and core to core communication scenarios.
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*
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* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
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* implementation (so also the message buffer implementation, as message buffers
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* are built on top of stream buffers) assumes there is only one task or
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* interrupt that will write to the buffer (the writer), and only one task or
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* interrupt that will read from the buffer (the reader). It is safe for the
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* writer and reader to be different tasks or interrupts, but, unlike other
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* FreeRTOS objects, it is not safe to have multiple different writers or
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* multiple different readers. If there are to be multiple different writers
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* then the application writer must place each call to a writing API function
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* (such as xMessageBufferSend()) inside a critical section and set the send
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* block time to 0. Likewise, if there are to be multiple different readers
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* then the application writer must place each call to a reading API function
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* (such as xMessageBufferRead()) inside a critical section and set the receive
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* timeout to 0.
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*
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* Message buffers hold variable length messages. To enable that, when a
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* message is written to the message buffer an additional sizeof( size_t ) bytes
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* are also written to store the message's length (that happens internally, with
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* the API function). sizeof( size_t ) is typically 4 bytes on a 32-bit
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* architecture, so writing a 10 byte message to a message buffer on a 32-bit
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* architecture will actually reduce the available space in the message buffer
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* by 14 bytes (10 byte are used by the message, and 4 bytes to hold the length
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* of the message).
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*/
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#ifndef FREERTOS_MESSAGE_BUFFER_H
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#define FREERTOS_MESSAGE_BUFFER_H
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/* Message buffers are built onto of stream buffers. */
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#include "stream_buffer.h"
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#if defined( __cplusplus )
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extern "C" {
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#endif
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/**
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* Type by which message buffers are referenced. For example, a call to
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* xMessageBufferCreate() returns an MessageBufferHandle_t variable that can
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* then be used as a parameter to xMessageBufferSend(), xMessageBufferReceive(),
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* etc.
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*/
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typedef void * MessageBufferHandle_t;
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/*-----------------------------------------------------------*/
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/**
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* message_buffer.h
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*
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<pre>
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MessageBufferHandle_t xMessageBufferCreate( size_t xBufferSizeBytes );
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</pre>
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*
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* Creates a new message buffer using dynamically allocated memory. See
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* xMessageBufferCreateStatic() for a version that uses statically allocated
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* memory (memory that is allocated at compile time).
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*
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* configSUPPORT_DYNAMIC_ALLOCATION must be set to 1 or left undefined in
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* FreeRTOSConfig.h for xMessageBufferCreate() to be available.
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*
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* @param xBufferSizeBytes The total number of bytes (not messages) the message
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* buffer will be able to hold at any one time. When a message is written to
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* the message buffer an additional sizeof( size_t ) bytes are also written to
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* store the message's length. sizeof( size_t ) is typically 4 bytes on a
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* 32-bit architecture, so on most 32-bit architectures a 10 byte message will
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* take up 14 bytes of message buffer space.
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*
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* @return If NULL is returned, then the message buffer cannot be created
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* because there is insufficient heap memory available for FreeRTOS to allocate
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* the message buffer data structures and storage area. A non-NULL value being
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* returned indicates that the message buffer has been created successfully -
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* the returned value should be stored as the handle to the created message
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* buffer.
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*
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* Example use:
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<pre>
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void vAFunction( void )
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{
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MessageBufferHandle_t xMessageBuffer;
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const size_t xMessageBufferSizeBytes = 100;
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// Create a message buffer that can hold 100 bytes. The memory used to hold
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// both the message buffer structure and the messages themselves is allocated
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// dynamically. Each message added to the buffer consumes an additional 4
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// bytes which are used to hold the lengh of the message.
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xMessageBuffer = xMessageBufferCreate( xMessageBufferSizeBytes );
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if( xMessageBuffer == NULL )
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{
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// There was not enough heap memory space available to create the
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// message buffer.
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}
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else
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{
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// The message buffer was created successfully and can now be used.
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}
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</pre>
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* \defgroup xMessageBufferCreate xMessageBufferCreate
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* \ingroup MessageBufferManagement
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*/
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#define xMessageBufferCreate( xBufferSizeBytes ) ( MessageBufferHandle_t ) xStreamBufferGenericCreate( xBufferSizeBytes, ( size_t ) 0, pdTRUE )
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/**
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* message_buffer.h
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*
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<pre>
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MessageBufferHandle_t xMessageBufferCreateStatic( size_t xBufferSizeBytes,
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uint8_t *pucMessageBufferStorageArea,
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StaticMessageBuffer_t *pxStaticMessageBuffer );
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</pre>
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* Creates a new message buffer using statically allocated memory. See
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* xMessageBufferCreate() for a version that uses dynamically allocated memory.
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*
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* @param xBufferSizeBytes The size, in bytes, of the buffer pointed to by the
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* pucMessageBufferStorageArea parameter. When a message is written to the
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* message buffer an additional sizeof( size_t ) bytes are also written to store
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* the message's length. sizeof( size_t ) is typically 4 bytes on a 32-bit
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* architecture, so on most 32-bit architecture a 10 byte message will take up
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* 14 bytes of message buffer space. The maximum number of bytes that can be
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* stored in the message buffer is actually (xBufferSizeBytes - 1).
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*
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* @param pucMessageBufferStorageArea Must point to a uint8_t array that is at
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* least xBufferSizeBytes + 1 big. This is the array to which messages are
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* copied when they are written to the message buffer.
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*
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* @param pxStaticMessageBuffer Must point to a variable of type
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* StaticMessageBuffer_t, which will be used to hold the message buffer's data
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* structure.
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*
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* @return If the message buffer is created successfully then a handle to the
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* created message buffer is returned. If either pucMessageBufferStorageArea or
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* pxStaticmessageBuffer are NULL then NULL is returned.
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*
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* Example use:
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<pre>
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// Used to dimension the array used to hold the messages. The available space
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// will actually be one less than this, so 999.
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#define STORAGE_SIZE_BYTES 1000
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// Defines the memory that will actually hold the messages within the message
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// buffer.
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static uint8_t ucStorageBuffer[ STORAGE_SIZE_BYTES ];
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// The variable used to hold the message buffer structure.
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StaticMessageBuffer_t xMessageBufferStruct;
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void MyFunction( void )
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{
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MessageBufferHandle_t xMessageBuffer;
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xMessageBuffer = xMessageBufferCreateStatic( sizeof( ucBufferStorage ),
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ucBufferStorage,
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&xMessageBufferStruct );
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// As neither the pucMessageBufferStorageArea or pxStaticMessageBuffer
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// parameters were NULL, xMessageBuffer will not be NULL, and can be used to
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// reference the created message buffer in other message buffer API calls.
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// Other code that uses the message buffer can go here.
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}
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</pre>
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* \defgroup xMessageBufferCreateStatic xMessageBufferCreateStatic
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* \ingroup MessageBufferManagement
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*/
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#define xMessageBufferCreateStatic( xBufferSizeBytes, pucMessageBufferStorageArea, pxStaticMessageBuffer ) ( MessageBufferHandle_t ) xStreamBufferGenericCreateStatic( xBufferSizeBytes, 0, pdTRUE, pucMessageBufferStorageArea, pxStaticMessageBuffer )
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/**
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* message_buffer.h
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*
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<pre>
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size_t xMessageBufferSend( MessageBufferHandle_t xMessageBuffer,
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const void *pvTxData,
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size_t xDataLengthBytes,
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TickType_t xTicksToWait );
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<pre>
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*
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* Sends a discrete message to the message buffer. The message can be any
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* length that fits within the buffer's free space, and is copied into the
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* buffer.
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*
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* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
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* implementation (so also the message buffer implementation, as message buffers
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* are built on top of stream buffers) assumes there is only one task or
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* interrupt that will write to the buffer (the writer), and only one task or
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* interrupt that will read from the buffer (the reader). It is safe for the
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* writer and reader to be different tasks or interrupts, but, unlike other
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* FreeRTOS objects, it is not safe to have multiple different writers or
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* multiple different readers. If there are to be multiple different writers
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* then the application writer must place each call to a writing API function
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* (such as xMessageBufferSend()) inside a critical section and set the send
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* block time to 0. Likewise, if there are to be multiple different readers
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* then the application writer must place each call to a reading API function
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* (such as xMessageBufferRead()) inside a critical section and set the receive
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* block time to 0.
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*
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* Use xMessageBufferSend() to write to a message buffer from a task. Use
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* xMessageBufferSendFromISR() to write to a message buffer from an interrupt
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* service routine (ISR).
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*
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* @param xMessageBuffer The handle of the message buffer to which a message is
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* being sent.
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*
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* @param pvTxData A pointer to the message that is to be copied into the
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* message buffer.
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*
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* @param xDataLengthBytes The length of the message. That is, the number of
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* bytes to copy from pvTxData into the message buffer. When a message is
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* written to the message buffer an additional sizeof( size_t ) bytes are also
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* written to store the message's length. sizeof( size_t ) is typically 4 bytes
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* on a 32-bit architecture, so on most 32-bit architecture setting
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* xDataLengthBytes to 20 will reduce the free space in the message buffer by 24
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* bytes (20 bytes of message data and 4 bytes to hold the message length).
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*
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* @param xTicksToWait The maximum amount of time the calling task should remain
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* in the Blocked state to wait for enough space to become available in the
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* message buffer, should the message buffer have insufficient space when
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* xMessageBufferSend() is called. The calling task will never block if
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* xTicksToWait is zero. The block time is specified in tick periods, so the
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* absolute time it represents is dependent on the tick frequency. The macro
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* pdMS_TO_TICKS() can be used to convert a time specified in milliseconds into
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* a time specified in ticks. Setting xTicksToWait to portMAX_DELAY will cause
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* the task to wait indefinitely (without timing out), provided
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* INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h. Tasks do not use any
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* CPU time when they are in the Blocked state.
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*
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* @return The number of bytes written to the message buffer. If the call to
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* xMessageBufferSend() times out before there was enough space to write the
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* message into the message buffer then zero is returned. If the call did not
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* time out then xDataLengthBytes is returned.
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*
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* Example use:
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<pre>
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void vAFunction( MessageBufferHandle_t xMessageBuffer )
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{
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size_t xBytesSent;
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uint8_t ucArrayToSend[] = { 0, 1, 2, 3 };
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char *pcStringToSend = "String to send";
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const TickType_t x100ms = pdMS_TO_TICKS( 100 );
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// Send an array to the message buffer, blocking for a maximum of 100ms to
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// wait for enough space to be available in the message buffer.
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xBytesSent = xMessageBufferSend( xMessageBuffer, ( void * ) ucArrayToSend, sizeof( ucArrayToSend ), x100ms );
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if( xBytesSent != sizeof( ucArrayToSend ) )
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{
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// The call to xMessageBufferSend() times out before there was enough
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// space in the buffer for the data to be written.
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}
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// Send the string to the message buffer. Return immediately if there is
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// not enough space in the buffer.
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xBytesSent = xMessageBufferSend( xMessageBuffer, ( void * ) pcStringToSend, strlen( pcStringToSend ), 0 );
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if( xBytesSent != strlen( pcStringToSend ) )
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{
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// The string could not be added to the message buffer because there was
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// not enough free space in the buffer.
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}
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}
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</pre>
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* \defgroup xMessageBufferSend xMessageBufferSend
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* \ingroup MessageBufferManagement
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*/
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#define xMessageBufferSend( xMessageBuffer, pvTxData, xDataLengthBytes, xTicksToWait ) xStreamBufferSend( ( StreamBufferHandle_t ) xMessageBuffer, pvTxData, xDataLengthBytes, xTicksToWait )
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/**
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* message_buffer.h
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*
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<pre>
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size_t xMessageBufferSendFromISR( MessageBufferHandle_t xMessageBuffer,
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const void *pvTxData,
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size_t xDataLengthBytes,
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BaseType_t *pxHigherPriorityTaskWoken );
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<pre>
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*
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* Interrupt safe version of the API function that sends a discrete message to
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* the message buffer. The message can be any length that fits within the
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* buffer's free space, and is copied into the buffer.
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*
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* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
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* implementation (so also the message buffer implementation, as message buffers
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* are built on top of stream buffers) assumes there is only one task or
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* interrupt that will write to the buffer (the writer), and only one task or
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* interrupt that will read from the buffer (the reader). It is safe for the
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* writer and reader to be different tasks or interrupts, but, unlike other
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* FreeRTOS objects, it is not safe to have multiple different writers or
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* multiple different readers. If there are to be multiple different writers
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* then the application writer must place each call to a writing API function
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* (such as xMessageBufferSend()) inside a critical section and set the send
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* block time to 0. Likewise, if there are to be multiple different readers
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* then the application writer must place each call to a reading API function
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* (such as xMessageBufferRead()) inside a critical section and set the receive
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* block time to 0.
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*
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* Use xMessageBufferSend() to write to a message buffer from a task. Use
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* xMessageBufferSendFromISR() to write to a message buffer from an interrupt
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* service routine (ISR).
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*
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* @param xMessageBuffer The handle of the message buffer to which a message is
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* being sent.
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*
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* @param pvTxData A pointer to the message that is to be copied into the
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* message buffer.
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*
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* @param xDataLengthBytes The length of the message. That is, the number of
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* bytes to copy from pvTxData into the message buffer. When a message is
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* written to the message buffer an additional sizeof( size_t ) bytes are also
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* written to store the message's length. sizeof( size_t ) is typically 4 bytes
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* on a 32-bit architecture, so on most 32-bit architecture setting
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* xDataLengthBytes to 20 will reduce the free space in the message buffer by 24
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* bytes (20 bytes of message data and 4 bytes to hold the message length).
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*
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* @param pxHigherPriorityTaskWoken It is possible that a message buffer will
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* have a task blocked on it waiting for data. Calling
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* xMessageBufferSendFromISR() can make data available, and so cause a task that
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* was waiting for data to leave the Blocked state. If calling
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* xMessageBufferSendFromISR() causes a task to leave the Blocked state, and the
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* unblocked task has a priority higher than the currently executing task (the
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* task that was interrupted), then, internally, xMessageBufferSendFromISR()
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* will set *pxHigherPriorityTaskWoken to pdTRUE. If
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* xMessageBufferSendFromISR() sets this value to pdTRUE, then normally a
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* context switch should be performed before the interrupt is exited. This will
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* ensure that the interrupt returns directly to the highest priority Ready
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* state task. *pxHigherPriorityTaskWoken should be set to pdFALSE before it
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* is passed into the function. See the code example below for an example.
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*
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* @return The number of bytes actually written to the message buffer. If the
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* message buffer didn't have enough free space for the message to be stored
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* then 0 is returned, otherwise xDataLengthBytes is returned.
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*
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* Example use:
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<pre>
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// A message buffer that has already been created.
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MessageBufferHandle_t xMessageBuffer;
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void vAnInterruptServiceRoutine( void )
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{
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size_t xBytesSent;
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char *pcStringToSend = "String to send";
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BaseType_t xHigherPriorityTaskWoken = pdFALSE; // Initialised to pdFALSE.
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// Attempt to send the string to the message buffer.
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xBytesSent = xMessageBufferSendFromISR( xMessageBuffer,
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( void * ) pcStringToSend,
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strlen( pcStringToSend ),
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&xHigherPriorityTaskWoken );
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if( xBytesSent != strlen( pcStringToSend ) )
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{
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// The string could not be added to the message buffer because there was
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// not enough free space in the buffer.
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}
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// If xHigherPriorityTaskWoken was set to pdTRUE inside
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// xMessageBufferSendFromISR() then a task that has a priority above the
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// priority of the currently executing task was unblocked and a context
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// switch should be performed to ensure the ISR returns to the unblocked
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// task. In most FreeRTOS ports this is done by simply passing
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// xHigherPriorityTaskWoken into taskYIELD_FROM_ISR(), which will test the
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// variables value, and perform the context switch if necessary. Check the
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// documentation for the port in use for port specific instructions.
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taskYIELD_FROM_ISR( xHigherPriorityTaskWoken );
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}
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</pre>
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* \defgroup xMessageBufferSendFromISR xMessageBufferSendFromISR
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* \ingroup MessageBufferManagement
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*/
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#define xMessageBufferSendFromISR( xMessageBuffer, pvTxData, xDataLengthBytes, pxHigherPriorityTaskWoken ) xStreamBufferSendFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pvTxData, xDataLengthBytes, pxHigherPriorityTaskWoken )
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/**
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* message_buffer.h
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*
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<pre>
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size_t xMessageBufferReceive( MessageBufferHandle_t xMessageBuffer,
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void *pvRxData,
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size_t xBufferLengthBytes,
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TickType_t xTicksToWait );
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</pre>
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*
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* Receives a discrete message from a message buffer. Messages can be of
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* variable length and are copied out of the buffer.
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*
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* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
|
|
* implementation (so also the message buffer implementation, as message buffers
|
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* are built on top of stream buffers) assumes there is only one task or
|
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* interrupt that will write to the buffer (the writer), and only one task or
|
|
* interrupt that will read from the buffer (the reader). It is safe for the
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* writer and reader to be different tasks or interrupts, but, unlike other
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* FreeRTOS objects, it is not safe to have multiple different writers or
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* multiple different readers. If there are to be multiple different writers
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* then the application writer must place each call to a writing API function
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* (such as xMessageBufferSend()) inside a critical section and set the send
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* block time to 0. Likewise, if there are to be multiple different readers
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|
* then the application writer must place each call to a reading API function
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* (such as xMessageBufferRead()) inside a critical section and set the receive
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* block time to 0.
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*
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* Use xMessageBufferReceive() to read from a message buffer from a task. Use
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* xMessageBufferReceiveFromISR() to read from a message buffer from an
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* interrupt service routine (ISR).
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*
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* @param xMessageBuffer The handle of the message buffer from which a message
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* is being received.
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*
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* @param pvRxData A pointer to the buffer into which the received message is
|
|
* to be copied.
|
|
*
|
|
* @param xBufferLengthBytes The length of the buffer pointed to by the pvRxData
|
|
* parameter. This sets the maximum length of the message that can be received.
|
|
* If xBufferLengthBytes is too small to hold the next message then the message
|
|
* will be left in the message buffer and 0 will be returned.
|
|
*
|
|
* @param xTicksToWait The maximum amount of time the task should remain in the
|
|
* Blocked state to wait for a message, should the message buffer be empty.
|
|
* xMessageBufferReceive() will return immediately if xTicksToWait is zero and
|
|
* the message buffer is empty. The block time is specified in tick periods, so
|
|
* the absolute time it represents is dependent on the tick frequency. The
|
|
* macro pdMS_TO_TICKS() can be used to convert a time specified in milliseconds
|
|
* into a time specified in ticks. Setting xTicksToWait to portMAX_DELAY will
|
|
* cause the task to wait indefinitely (without timing out), provided
|
|
* INCLUDE_vTaskSuspend is set to 1 in FreeRTOSConfig.h. Tasks do not use any
|
|
* CPU time when they are in the Blocked state.
|
|
*
|
|
* @return The length, in bytes, of the message read from the message buffer, if
|
|
* any. If xMessageBufferReceive() times out before a message became available
|
|
* then zero is returned. If the length of the message is greater than
|
|
* xBufferLengthBytes then the message will be left in the message buffer and
|
|
* zero is returned.
|
|
*
|
|
* Example use:
|
|
<pre>
|
|
void vAFunction( MessageBuffer_t xMessageBuffer )
|
|
{
|
|
uint8_t ucRxData[ 20 ];
|
|
size_t xReceivedBytes;
|
|
const TickType_t xBlockTime = pdMS_TO_TICKS( 20 );
|
|
|
|
// Receive the next message from the message buffer. Wait in the Blocked
|
|
// state (so not using any CPU processing time) for a maximum of 100ms for
|
|
// a message to become available.
|
|
xReceivedBytes = xMessageBufferReceive( xMessageBuffer,
|
|
( void * ) ucRxData,
|
|
sizeof( ucRxData ),
|
|
xBlockTime );
|
|
|
|
if( xReceivedBytes > 0 )
|
|
{
|
|
// A ucRxData contains a message that is xReceivedBytes long. Process
|
|
// the message here....
|
|
}
|
|
}
|
|
</pre>
|
|
* \defgroup xMessageBufferReceive xMessageBufferReceive
|
|
* \ingroup MessageBufferManagement
|
|
*/
|
|
#define xMessageBufferReceive( xMessageBuffer, pvRxData, xBufferLengthBytes, xTicksToWait ) xStreamBufferReceive( ( StreamBufferHandle_t ) xMessageBuffer, pvRxData, xBufferLengthBytes, xTicksToWait )
|
|
|
|
|
|
/**
|
|
* message_buffer.h
|
|
*
|
|
<pre>
|
|
size_t xMessageBufferReceiveFromISR( MessageBufferHandle_t xMessageBuffer,
|
|
void *pvRxData,
|
|
size_t xBufferLengthBytes,
|
|
BaseType_t *pxHigherPriorityTaskWoken );
|
|
</pre>
|
|
*
|
|
* An interrupt safe version of the API function that receives a discrete
|
|
* message from a message buffer. Messages can be of variable length and are
|
|
* copied out of the buffer.
|
|
*
|
|
* ***NOTE***: Uniquely among FreeRTOS objects, the stream buffer
|
|
* implementation (so also the message buffer implementation, as message buffers
|
|
* are built on top of stream buffers) assumes there is only one task or
|
|
* interrupt that will write to the buffer (the writer), and only one task or
|
|
* interrupt that will read from the buffer (the reader). It is safe for the
|
|
* writer and reader to be different tasks or interrupts, but, unlike other
|
|
* FreeRTOS objects, it is not safe to have multiple different writers or
|
|
* multiple different readers. If there are to be multiple different writers
|
|
* then the application writer must place each call to a writing API function
|
|
* (such as xMessageBufferSend()) inside a critical section and set the send
|
|
* block time to 0. Likewise, if there are to be multiple different readers
|
|
* then the application writer must place each call to a reading API function
|
|
* (such as xMessageBufferRead()) inside a critical section and set the receive
|
|
* block time to 0.
|
|
*
|
|
* Use xMessageBufferReceive() to read from a message buffer from a task. Use
|
|
* xMessageBufferReceiveFromISR() to read from a message buffer from an
|
|
* interrupt service routine (ISR).
|
|
*
|
|
* @param xMessageBuffer The handle of the message buffer from which a message
|
|
* is being received.
|
|
*
|
|
* @param pvRxData A pointer to the buffer into which the received message is
|
|
* to be copied.
|
|
*
|
|
* @param xBufferLengthBytes The length of the buffer pointed to by the pvRxData
|
|
* parameter. This sets the maximum length of the message that can be received.
|
|
* If xBufferLengthBytes is too small to hold the next message then the message
|
|
* will be left in the message buffer and 0 will be returned.
|
|
*
|
|
* @param pxHigherPriorityTaskWoken It is possible that a message buffer will
|
|
* have a task blocked on it waiting for space to become available. Calling
|
|
* xMessageBufferReceiveFromISR() can make space available, and so cause a task
|
|
* that is waiting for space to leave the Blocked state. If calling
|
|
* xMessageBufferReceiveFromISR() causes a task to leave the Blocked state, and
|
|
* the unblocked task has a priority higher than the currently executing task
|
|
* (the task that was interrupted), then, internally,
|
|
* xMessageBufferReceiveFromISR() will set *pxHigherPriorityTaskWoken to pdTRUE.
|
|
* If xMessageBufferReceiveFromISR() sets this value to pdTRUE, then normally a
|
|
* context switch should be performed before the interrupt is exited. That will
|
|
* ensure the interrupt returns directly to the highest priority Ready state
|
|
* task. *pxHigherPriorityTaskWoken should be set to pdFALSE before it is
|
|
* passed into the function. See the code example below for an example.
|
|
*
|
|
* @return The length, in bytes, of the message read from the message buffer, if
|
|
* any.
|
|
*
|
|
* Example use:
|
|
<pre>
|
|
// A message buffer that has already been created.
|
|
MessageBuffer_t xMessageBuffer;
|
|
|
|
void vAnInterruptServiceRoutine( void )
|
|
{
|
|
uint8_t ucRxData[ 20 ];
|
|
size_t xReceivedBytes;
|
|
BaseType_t xHigherPriorityTaskWoken = pdFALSE; // Initialised to pdFALSE.
|
|
|
|
// Receive the next message from the message buffer.
|
|
xReceivedBytes = xMessageBufferReceiveFromISR( xMessageBuffer,
|
|
( void * ) ucRxData,
|
|
sizeof( ucRxData ),
|
|
&xHigherPriorityTaskWoken );
|
|
|
|
if( xReceivedBytes > 0 )
|
|
{
|
|
// A ucRxData contains a message that is xReceivedBytes long. Process
|
|
// the message here....
|
|
}
|
|
|
|
// If xHigherPriorityTaskWoken was set to pdTRUE inside
|
|
// xMessageBufferReceiveFromISR() then a task that has a priority above the
|
|
// priority of the currently executing task was unblocked and a context
|
|
// switch should be performed to ensure the ISR returns to the unblocked
|
|
// task. In most FreeRTOS ports this is done by simply passing
|
|
// xHigherPriorityTaskWoken into taskYIELD_FROM_ISR(), which will test the
|
|
// variables value, and perform the context switch if necessary. Check the
|
|
// documentation for the port in use for port specific instructions.
|
|
taskYIELD_FROM_ISR( xHigherPriorityTaskWoken );
|
|
}
|
|
</pre>
|
|
* \defgroup xMessageBufferReceiveFromISR xMessageBufferReceiveFromISR
|
|
* \ingroup MessageBufferManagement
|
|
*/
|
|
#define xMessageBufferReceiveFromISR( xMessageBuffer, pvRxData, xBufferLengthBytes, pxHigherPriorityTaskWoken ) xStreamBufferReceiveFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pvRxData, xBufferLengthBytes, pxHigherPriorityTaskWoken )
|
|
|
|
/**
|
|
* message_buffer.h
|
|
*
|
|
<pre>
|
|
void vMessageBufferDelete( MessageBufferHandle_t xMessageBuffer );
|
|
</pre>
|
|
*
|
|
* Deletes a message buffer that was previously created using a call to
|
|
* xMessageBufferCreate() or xMessageBufferCreateStatic(). If the message
|
|
* buffer was created using dynamic memory (that is, by xMessageBufferCreate()),
|
|
* then the allocated memory is freed.
|
|
*
|
|
* A message buffer handle must not be used after the message buffer has been
|
|
* deleted.
|
|
*
|
|
* @param xMessageBuffer The handle of the message buffer to be deleted.
|
|
*
|
|
*/
|
|
#define vMessageBufferDelete( xMessageBuffer ) vStreamBufferDelete( ( StreamBufferHandle_t ) xMessageBuffer )
|
|
|
|
/**
|
|
* message_buffer.h
|
|
<pre>
|
|
BaseType_t xMessageBufferIsFull( MessageBufferHandle_t xMessageBuffer ) );
|
|
</pre>
|
|
*
|
|
* Tests to see if a message buffer is full. A message buffer is full if it
|
|
* cannot accept any more messages, of any size, until space is made available
|
|
* by a message being removed from the message buffer.
|
|
*
|
|
* @param xMessageBuffer The handle of the message buffer being queried.
|
|
*
|
|
* @return If the message buffer referenced by xMessageBuffer is full then
|
|
* pdTRUE is returned. Otherwise pdFALSE is returned.
|
|
*/
|
|
#define xMessageBufferIsFull( xMessageBuffer ) xStreamBufferIsFull( ( StreamBufferHandle_t ) xMessageBuffer )
|
|
|
|
/**
|
|
* message_buffer.h
|
|
<pre>
|
|
BaseType_t xMessageBufferIsEmpty( MessageBufferHandle_t xMessageBuffer ) );
|
|
</pre>
|
|
*
|
|
* Tests to see if a message buffer is empty (does not contain any messages).
|
|
*
|
|
* @param xMessageBuffer The handle of the message buffer being queried.
|
|
*
|
|
* @return If the message buffer referenced by xMessageBuffer is empty then
|
|
* pdTRUE is returned. Otherwise pdFALSE is returned.
|
|
*
|
|
*/
|
|
#define xMessageBufferIsEmpty( xMessageBuffer ) xStreamBufferIsEmpty( ( StreamBufferHandle_t ) xMessageBuffer )
|
|
|
|
/**
|
|
* message_buffer.h
|
|
<pre>
|
|
BaseType_t xMessageBufferReset( MessageBufferHandle_t xMessageBuffer );
|
|
</pre>
|
|
*
|
|
* Resets a message buffer to its initial empty state, discarding any message it
|
|
* contained.
|
|
*
|
|
* A message buffer can only be reset if there are no tasks blocked on it.
|
|
*
|
|
* @param xMessageBuffer The handle of the message buffer being reset.
|
|
*
|
|
* @return If the message buffer was reset then pdPASS is returned. If the
|
|
* message buffer could not be reset because either there was a task blocked on
|
|
* the message queue to wait for space to become available, or to wait for a
|
|
* a message to be available, then pdFAIL is returned.
|
|
*
|
|
* \defgroup xMessageBufferReset xMessageBufferReset
|
|
* \ingroup MessageBufferManagement
|
|
*/
|
|
#define xMessageBufferReset( xMessageBuffer ) xStreamBufferReset( ( StreamBufferHandle_t ) xMessageBuffer )
|
|
|
|
|
|
/**
|
|
* message_buffer.h
|
|
<pre>
|
|
size_t xMessageBufferSpaceAvailable( MessageBufferHandle_t xMessageBuffer ) );
|
|
</pre>
|
|
* Returns the number of bytes of free space in the message buffer.
|
|
*
|
|
* @param xMessageBuffer The handle of the message buffer being queried.
|
|
*
|
|
* @return The number of bytes that can be written to the message buffer before
|
|
* the message buffer would be full. When a message is written to the message
|
|
* buffer an additional sizeof( size_t ) bytes are also written to store the
|
|
* message's length. sizeof( size_t ) is typically 4 bytes on a 32-bit
|
|
* architecture, so if xMessageBufferSpacesAvailable() returns 10, then the size
|
|
* of the largest message that can be written to the message buffer is 6 bytes.
|
|
*
|
|
* \defgroup xMessageBufferSpaceAvailable xMessageBufferSpaceAvailable
|
|
* \ingroup MessageBufferManagement
|
|
*/
|
|
#define xMessageBufferSpaceAvailable( xMessageBuffer ) xStreamBufferSpacesAvailable( ( StreamBufferHandle_t ) xMessageBuffer )
|
|
|
|
/**
|
|
* message_buffer.h
|
|
*
|
|
<pre>
|
|
BaseType_t xMessageBufferSendCompletedFromISR( MessageBufferHandle_t xStreamBuffer, BaseType_t *pxHigherPriorityTaskWoken );
|
|
</pre>
|
|
*
|
|
* For advanced users only.
|
|
*
|
|
* The sbSEND_COMPLETED() macro is called from within the FreeRTOS APIs when
|
|
* data is sent to a message buffer or stream buffer. If there was a task that
|
|
* was blocked on the message or stream buffer waiting for data to arrive then
|
|
* the sbSEND_COMPLETED() macro sends a notification to the task to remove it
|
|
* from the Blocked state. xMessageBufferSendCompletedFromISR() does the same
|
|
* thing. It is provided to enable application writers to implement their own
|
|
* version of sbSEND_COMPLETED(), and MUST NOT BE USED AT ANY OTHER TIME.
|
|
*
|
|
* See the example implemented in FreeRTOS/Demo/Minimal/MessageBufferAMP.c for
|
|
* additional information.
|
|
*
|
|
* @param xStreamBuffer The handle of the stream buffer to which data was
|
|
* written.
|
|
*
|
|
* @param pxHigherPriorityTaskWoken *pxHigherPriorityTaskWoken should be
|
|
* initialised to pdFALSE before it is passed into
|
|
* xMessageBufferSendCompletedFromISR(). If calling
|
|
* xMessageBufferSendCompletedFromISR() removes a task from the Blocked state,
|
|
* and the task has a priority above the priority of the currently running task,
|
|
* then *pxHigherPriorityTaskWoken will get set to pdTRUE indicating that a
|
|
* context switch should be performed before exiting the ISR.
|
|
*
|
|
* @return If a task was removed from the Blocked state then pdTRUE is returned.
|
|
* Otherwise pdFALSE is returned.
|
|
*
|
|
* \defgroup xMessageBufferSendCompletedFromISR xMessageBufferSendCompletedFromISR
|
|
* \ingroup StreamBufferManagement
|
|
*/
|
|
#define xMessageBufferSendCompletedFromISR( xMessageBuffer, pxHigherPriorityTaskWoken ) xStreamBufferSendCompletedFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pxHigherPriorityTaskWoken )
|
|
|
|
/**
|
|
* message_buffer.h
|
|
*
|
|
<pre>
|
|
BaseType_t xMessageBufferReceiveCompletedFromISR( MessageBufferHandle_t xStreamBuffer, BaseType_t *pxHigherPriorityTaskWoken );
|
|
</pre>
|
|
*
|
|
* For advanced users only.
|
|
*
|
|
* The sbRECEIVE_COMPLETED() macro is called from within the FreeRTOS APIs when
|
|
* data is read out of a message buffer or stream buffer. If there was a task
|
|
* that was blocked on the message or stream buffer waiting for data to arrive
|
|
* then the sbRECEIVE_COMPLETED() macro sends a notification to the task to
|
|
* remove it from the Blocked state. xMessageBufferReceiveCompletedFromISR()
|
|
* does the same thing. It is provided to enable application writers to
|
|
* implement their own version of sbRECEIVE_COMPLETED(), and MUST NOT BE USED AT
|
|
* ANY OTHER TIME.
|
|
*
|
|
* See the example implemented in FreeRTOS/Demo/Minimal/MessageBufferAMP.c for
|
|
* additional information.
|
|
*
|
|
* @param xStreamBuffer The handle of the stream buffer from which data was
|
|
* read.
|
|
*
|
|
* @param pxHigherPriorityTaskWoken *pxHigherPriorityTaskWoken should be
|
|
* initialised to pdFALSE before it is passed into
|
|
* xMessageBufferReceiveCompletedFromISR(). If calling
|
|
* xMessageBufferReceiveCompletedFromISR() removes a task from the Blocked state,
|
|
* and the task has a priority above the priority of the currently running task,
|
|
* then *pxHigherPriorityTaskWoken will get set to pdTRUE indicating that a
|
|
* context switch should be performed before exiting the ISR.
|
|
*
|
|
* @return If a task was removed from the Blocked state then pdTRUE is returned.
|
|
* Otherwise pdFALSE is returned.
|
|
*
|
|
* \defgroup xMessageBufferReceiveCompletedFromISR xMessageBufferReceiveCompletedFromISR
|
|
* \ingroup StreamBufferManagement
|
|
*/
|
|
#define xMessageBufferReceiveCompletedFromISR( xMessageBuffer, pxHigherPriorityTaskWoken ) xStreamBufferReceiveCompletedFromISR( ( StreamBufferHandle_t ) xMessageBuffer, pxHigherPriorityTaskWoken )
|
|
|
|
#if defined( __cplusplus )
|
|
} /* extern "C" */
|
|
#endif
|
|
|
|
#endif /* !defined( FREERTOS_MESSAGE_BUFFER_H ) */
|