InterTask Communication using Multiple Queues

This code shows a basic logic to perform inter-task communication using multiple queues

GPIO Functions:

• GPIO2 : output ( built-in led on Devkit-V1 )

Understanding the Flow:

• This code is developed for ESP32 on Embedded C Language using FreeRTOS.
• FreeRTOS task don't have the provision to return values.
• That said, one can either use global variables to track changes in values but is not the most appropriate way.
• This is where "Queue" comes into picture, enabling inter-task communications.

Queues in FreeRTOS:

• As the name suggests, Queues acts like a stacked list and mostly preferred in FIFO ( First In First Out ).
• There are various Queue operations available, but in this program I will cover the basic functions.

Create a Queue-

• xQueueCreate( UBaseType_t uxQueueLength, UBaseType_t uxItemSize );
• uxQueueLength --> The maximum number of items the queue can hold at any one time.
• uxItemSize --> The size, in bytes, required to hold each item in the queue.
• Example --> xQueue1 = xQueueCreate( 10, sizeof( unsigned long ) );
• If created successfully, returns the handle or "NULL" otherwise.

Delete a Queue-

• vQueueDelete( QueueHandle_t xQueue );
• Deletes the queue with the provided handle "xQueue".

Send messages on Queue-

• xQueueSend( QueueHandle_t xQueue, const void * pvItemToQueue, TickType_t xTicksToWait );
• xQueue --> The handle to the queue on which the item is to be posted.
• pvItemToQueue --> A pointer to the item that is to be placed on the queue.
• xTicksToWait --> The maximum amount of time the task should block waiting for space to become available on the queue, should it already be full.
• Returns "pdTRUE" if the item was successfully posted, otherwise "errQUEUE_FULL".

Receive messages on Queue-

• *xQueueReceive( QueueHandle_t xQueue, void pvBuffer, TickType_t xTicksToWait );
• xQueue --> The handle to the queue on which the item is to be received.
• pvBuffer --> Pointer to the buffer into which the received item will be copied.
• xTicksToWait --> The maximum amount of time the task should block waiting for an item to receive should the queue be empty at the time of the call.
• Returns "pdTRUE" if an item was successfully received from the queue, otherwise "pdFALSE".