[Solved] Examine the following ISR code snippet for deferring processing using a queue:void ISR_Handler(void) { BaseType_t xHigherPriorityTaskWoken = pdFALSE;... }What is the main issue with this code? | FreeRTOS

FreeRTOS - Interrupt Management

Examine the following ISR code snippet for deferring processing using a queue:

void ISR_Handler(void) {
  BaseType_t xHigherPriorityTaskWoken = pdFALSE;
  xQueueSendFromISR(queueHandle, &data, &xHigherPriorityTaskWoken);
  portYIELD_FROM_ISR(xHigherPriorityTaskWoken);
}

What is the main issue with this code?

AxQueueSendFromISR is used incorrectly without checking return value

BxQueueSend should be used instead of xQueueSendFromISR inside ISR

CportYIELD_FROM_ISR should not be called in ISR

DxHigherPriorityTaskWoken should be initialized to pdTRUE

Step-by-Step Solution

Solution:

Step 1: Analyze API usage
xQueueSendFromISR returns a BaseType_t indicating success or failure.
Step 2: Identify missing check
The code does not check if xQueueSendFromISR succeeded, which can cause lost data if the queue is full.
Step 3: Confirm other options
xQueueSend is not ISR safe, portYIELD_FROM_ISR is correct, and xHigherPriorityTaskWoken should start as pdFALSE.
Final Answer:
Missing return value check of xQueueSendFromISR -> Option A
Quick Check:
Always check ISR API return values [OK]

Quick Trick: Always verify ISR API return values [OK]

Common Mistakes:

Using non-ISR safe APIs inside ISR
Ignoring return values of ISR-safe functions
Incorrect initialization of xHigherPriorityTaskWoken

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More FreeRTOS Quizzes

Examine the following ISR code snippet for deferring processing using a queue:

Step 1: Analyze API usage

Step 2: Identify missing check

Step 3: Confirm other options

Final Answer:

Quick Check:

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