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is a pointer to a variable that will contain an error code returned by this function.
OS_ERR_NONE
if If the call was successful and the message was posted to the task’s message queue.
OS_ERR_MSG_POOL_EMPTY
if If running out of OS_MSG to hold the message being posted.
OS_ERR_Q_MAX
if If the task’s message queue is full and cannot accept more messages.
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