You need to create a FreeRTOS task that executes precisely every 200 ms using vTaskDelayUntil(). The system tick rate is 1000 Hz. Which of the following code snippets correctly implements this?

hard📝 Application Q8 of 15

FreeRTOS - Task Scheduling

You need to create a FreeRTOS task that executes precisely every 200 ms using vTaskDelayUntil(). The system tick rate is 1000 Hz. Which of the following code snippets correctly implements this?

<pre>TickType_t xLastWakeTime = 0;
for (;;) {
    vTaskDelayUntil(&xLastWakeTime, pdMS_TO_TICKS(20));
    // Task code
}</pre>

<pre>TickType_t xLastWakeTime;
xLastWakeTime = 0;
for (;;) {
    vTaskDelayUntil(&xLastWakeTime, 200);
    // Task code
}</pre>

<pre>TickType_t xLastWakeTime = xTaskGetTickCount();
for (;;) {
    vTaskDelayUntil(&xLastWakeTime, pdMS_TO_TICKS(200));
    // Task code
}</pre>

<pre>TickType_t xLastWakeTime = xTaskGetTickCount();
for (;;) {
    vTaskDelayUntil(&xLastWakeTime, 200);
    // Task code
}</pre>

Step-by-Step Solution

Solution:

Step 1: Initialize xLastWakeTime
It must be initialized with current tick count using xTaskGetTickCount().
Step 2: Use pdMS_TO_TICKS macro
Convert 200 ms to ticks correctly with pdMS_TO_TICKS(200).
Step 3: Verify delay parameter
Passing 200 directly is incorrect unless tick rate is 1 kHz, but better to use macro for portability.

Final Answer:

TickType_t xLastWakeTime = xTaskGetTickCount(); for (;;) { vTaskDelayUntil(&xLastWakeTime, pdMS_TO_TICKS(200)); // Task code }
correctly initializes and uses pdMS_TO_TICKS.

Quick Check:
Check initialization and delay conversion [OK]

Quick Trick: Initialize lastWakeTime and use pdMS_TO_TICKS for delays [OK]

Common Mistakes:

Not initializing lastWakeTime before first call
Passing raw milliseconds instead of ticks
Using incorrect delay period

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More FreeRTOS Quizzes

You need to create a FreeRTOS task that executes precisely every 200 ms using vTaskDelayUntil(). The system tick rate is 1000 Hz. Which of the following code snippets correctly implements this?

Step 1: Initialize xLastWakeTime

Step 2: Use pdMS_TO_TICKS macro

Step 3: Verify delay parameter

Final Answer:

Quick Check:

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