TWI Slave Mode Programming Quiz

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Questions and Answers

What is the first step in programming a device in slave mode using TWI?

  • Receiving data from the master
  • Sending data to the master
  • Initializing the slave address (correct)
  • Listening for the master device

Which bit needs to be set to enable the TWI module?

  • TWAR
  • TWEN (correct)
  • TWINT
  • TWEA

In FreeRTOS, how are tasks identified for scheduling?

  • By their execution history
  • By their global variable state
  • By their priorities and dependencies (correct)
  • By their return type

What is the required function prototype for tasks in FreeRTOS?

<p>void function_name(void* parameter) (A)</p> Signup and view all the answers

Which component is essential for receiving data in TWI slave mode?

<p>TWDR (D)</p> Signup and view all the answers

What is the purpose of the configMAX_TASK_NAME_LEN parameter in FreeRTOSConfig.h?

<p>It sets the maximum length for a task's name. (C)</p> Signup and view all the answers

In FreeRTOS, what happens when vTaskDelete is called with a NULL parameter?

<p>It deletes the calling task (B)</p> Signup and view all the answers

What is a characteristic of tasks in a real-time operating system like FreeRTOS?

<p>They may be periodic with time constraints (C)</p> Signup and view all the answers

What does the sStackDepth parameter represent in a task's configuration?

<p>The size of the stack allocated in terms of words. (D)</p> Signup and view all the answers

What is the purpose of the TWINT flag in TWI slave mode?

<p>To show that data was received successfully (B)</p> Signup and view all the answers

What should be done if the pvParameters value is not being used in a task?

<p>It should be set to NULL as recommended. (D)</p> Signup and view all the answers

Which function should be used for sending messages to a queue from an ISR?

<p>xQueueSendtoBackFromISR() (B)</p> Signup and view all the answers

How can the number of waiting messages in a queue be checked?

<p>Using xQueueMessagesWaiting() (D)</p> Signup and view all the answers

Flashcards

Slave Mode TWI Programming

A method of communicating with a TWI (Two-Wire Interface) peripheral in a slave role, responding to requests from a master device.

TWI Initialization

Configuring the TWI module, setting the slave address and enabling the communication.

Real-Time Operating System (RTOS)

Software that manages multiple tasks within a microcontroller, assigning execution time and prioritizing tasks for real-time applications.

Task Function Prototype

The required structure of a function that serves as a task within an RTOS. It must return void and take a void pointer.

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vTaskDelete()

An RTOS function used to delete a task, including the calling task if given a NULL parameter.

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Task States (RTOS)

Describes the different conditions a task can be in within an RTOS, such as running or not running.

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xTaskCreate()

An RTOS function used to declare functions as tasks, with specific parameters like a function pointer and a name.

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Task Priorities

Control the relative importance of tasks, ensuring that critical tasks are executed first. The concept is essential for a real time OS.

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Task name length

The maximum length of a task's name, controlled by configMAX_TASK_NAME_LEN in FreeRTOSConfig.h.

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Task stack depth

Size of the stack allocated for a task, storing its configuration and register values when not running. Measured in words (system-dependent).

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Task parameters

A value passed to the task's entry function; set to NULL if not used.

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Queue creation

Creating a queue using xQueueCreate().

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Queue sending

Sending messages to a queue with xQueueSendToBack() or xQueueSendToFront() (not from ISRs) or using ISR-compatible functions (xQueueSendToBackFromISR, xQueueSendToFrontFromISR).

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Study Notes

TWI Slave Mode Programming

  • Initialization:

    • Set the slave address in the TWAR register.
      • 7 bits for the address.
      • 8th bit (TWGCE) is 1 for answering general calls.
    • Enable the TWI module by setting the TWEN bit in TWCR to 1.
    • Enable TWI, acknowledge generation by setting TWEN, TWINT, and TWEA bits in TWCR to 1.

  • Listening:

    • Poll the TWINT flag in TWCR to detect when the slave is addressed by a master.
    • Alternatively, use TWI interrupts.

  • Sending Data:

    • Copy the data byte to the TWDR register.
    • Set TWEN, TWEA, and TWINT bits in TWCR to 1 to start sending.
    • Poll the TWINT flag to confirm complete transmission.

  • Receiving Data:

    • Set TWEN and TWINT bits in TWCR to 1 to start receiving.
    • Poll the TWINT flag to confirm reception.
    • Read the received byte from the TWDR register.

RTC Connection

  • Real-time Clock (RTC) can be connected via I2C to a microcontroller.

FreeRTOS

  • Real-time Operating System (RTOS):

    • Designed for microcontrollers.
    • Primarily written in C.
    • Multitasking system for single-processor environments.
    • Kernel schedules tasks, utilizing CPU for concurrency.
    • Scheduling policy accounts for task dependencies and priorities.
    • Event-driven and periodic tasks managed to meet time constraints.
    • System failure results from unmet task constraints.

  • Task Implementation:

    • Implemented as C functions.
    • Return type is void.
    • Takes a void pointer parameter (flexible, unspecified data type, often of address size).
    • Must use vTaskDelete() to end a task (passing NULL ends the calling task).
    • State transitions between "running" and "not running".

  • Task Creation:

    • xTaskCreate() function creates tasks.
      • pvTaskCode: Pointer to the task function.
      • pcName: Descriptive task name (for debugging). Limited length (configMAX_TAKS_NAME_LEN in FreeRTOSConfig.h).
      • usStackDepth: Task stack size (number of words).
      • pvParameters: Optional parameter passed to task function (default NULL).

  • Queues:

    • Created with xQueueCreate().
    • Data can be added to the back or front of the queue using xQueueSendtoBack() or xQueueSendtoFront().
    • Use xQueueSendtoBackFromISR() or xQueueSendtoFrontFromISR() for sending from Interrupt Service Routines (ISRs) to avoid issues.
    • xQueueMessagesWaiting() monitors queue size.

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