Lightweight Message Queue

The way that tasks communicate with each other is by exchanging messages. Lightweight message queues are a simpler, low-overhead, implementation of standard MQX messages. Tasks send messages to lightweight message queues and receive messages from lightweight message queues. A message in the message pool has a fixed size, which is a multiple of 32 bits. Blocking reads and blocking writes are provided.

To use a lightweight message queue, a task executes the following steps:

• Initializing a lightweight message queue. Message pool has to be allocated statically before the initialization of this component. When the task initializes the lightweight message queue, it also specifies the number of messages to be created and the size of each message.
• Sending messages to the lightweight message queue. If the queue is full, the task either blocks and waits, or fails sending. Task can be blocked after the message is sent.
• Receiving messages from the lightweight message queue. If the queue is empty, the reading task performs timeout. If the lightweight message queue is empty, the reading task can be blocked.

There is no difference between the Lightweight Message Queue in the standard MQX and the MQX Lite. The list of Lightweight Message Queue component API functions ( _lwmsgq_ prefix) is provided together with detailed description of each function in the Freescale MQX™ Lite RTOS Reference Manual (MQXLITERM).

See the LWDEMO MQX Lite example code for the demonstration of the correct Lightweight Message Queue component usage. See MQX Lite Demo Applications for information about location of MQX Lite examples.