Nested interrupt handling in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable nested interrupts by setting the correct priority grouping.

FreeRTOS

NVIC_SetPriorityGrouping([1]);

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ANVIC_PRIORITYGROUP_3

BNVIC_PRIORITYGROUP_2

CNVIC_PRIORITYGROUP_4

DNVIC_PRIORITYGROUP_1

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing a priority grouping that disables subpriority levels.

Using NVIC_PRIORITYGROUP_4 which disables nested interrupts.

NVIC_PRIORITYGROUP_3 allows 4 bits for pre-emption priority and 0 bits for subpriority, enabling nested interrupts effectively.

2fill in blank

medium

Complete the code to set the priority of an interrupt to allow nesting.

FreeRTOS

NVIC_SetPriority(USART1_IRQn, [1]);

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A5

B15

C0

D255

Attempts:

3 left

💡 Hint

Common Mistakes

Setting priority to 0 which disables nesting by making it highest priority.

Using 255 which is invalid for priority levels.

Priority 5 is a moderate priority level allowing higher priority interrupts to pre-empt this one.

3fill in blank

hard

Fix the error in the interrupt handler declaration to support nesting.

FreeRTOS

void [1](void) {
    // Interrupt code
}

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AUSART1_Interrupt

BUSART1_IRQHandler

CUSART1_Handler

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect handler names that do not match the vector table.

Misspelling or wrong casing in the handler function name.

The correct interrupt handler name for USART1 is USART1_IRQHandler, matching the vector table.

4fill in blank

hard

Fill both blanks to correctly enable and set priority for a nested interrupt.

FreeRTOS

NVIC_EnableIRQ([1]);
NVIC_SetPriority([2], 3);

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ATIM2_IRQn

BUSART2_IRQn

CTIM3_IRQn

DUSART1_IRQn

Attempts:

3 left

💡 Hint

Common Mistakes

Using different interrupt names in enable and set priority calls.

Choosing interrupts not configured for nesting.

Enabling and setting priority for TIM2_IRQn allows nested interrupts on TIM2.

5fill in blank

hard

Fill all three blanks to create a nested interrupt safe critical section using FreeRTOS API.

FreeRTOS

taskENTER_CRITICAL();
[1]();
// Critical code
[2]();
NVIC_SetPriority([3], 1);

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AportDISABLE_INTERRUPTS

BportENABLE_INTERRUPTS

CTIM4_IRQn

DportSET_INTERRUPT_MASK

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to disable or enable interrupts properly.

Setting priority on wrong interrupt number.

Disable interrupts before critical code, enable after, and set priority for TIM4_IRQn to 1 for nesting.