configMAX_SYSCALL_INTERRUPT_PRIORITY in FreeRTOS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the maximum syscall interrupt priority.

FreeRTOS

#define configMAX_SYSCALL_INTERRUPT_PRIORITY [1]

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A5

B10

C3

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a priority value too high disables interrupts from calling FreeRTOS APIs.

Confusing priority numbering where lower numbers mean higher priority.

The value 3 is commonly used to set configMAX_SYSCALL_INTERRUPT_PRIORITY to allow interrupts with priority 3 and below to use FreeRTOS API calls.

2fill in blank

medium

Complete the code to define the interrupt priority mask using configMAX_SYSCALL_INTERRUPT_PRIORITY.

FreeRTOS

#define configKERNEL_INTERRUPT_PRIORITY ([1] << (8 - configPRIO_BITS))

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AconfigMAX_SYSCALL_INTERRUPT_PRIORITY - 1

BconfigMAX_SYSCALL_INTERRUPT_PRIORITY

CconfigMAX_SYSCALL_INTERRUPT_PRIORITY + 1

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Using configMAX_SYSCALL_INTERRUPT_PRIORITY instead of 0 for kernel priority.

Incorrect bit shifting causing wrong priority masking.

The kernel interrupt priority is usually set to 0 (lowest priority) shifted by the number of priority bits.

3fill in blank

hard

Fix the error in setting configMAX_SYSCALL_INTERRUPT_PRIORITY to allow safe API calls from interrupts.

FreeRTOS

#define configMAX_SYSCALL_INTERRUPT_PRIORITY [1]

Drag options to blanks, or click blank then click option'

A5

B255

C0

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Setting priority to 0 which is too high and disables API calls.

Using 255 which is too low and disables interrupt handling.

Setting configMAX_SYSCALL_INTERRUPT_PRIORITY to 5 allows interrupts with priority 5 and lower to safely call FreeRTOS API functions.

4fill in blank

hard

Fill both blanks to correctly define kernel and max syscall interrupt priorities.

FreeRTOS

#define configKERNEL_INTERRUPT_PRIORITY ([1] << (8 - configPRIO_BITS))
#define configMAX_SYSCALL_INTERRUPT_PRIORITY ([2])

Drag options to blanks, or click blank then click option'

A0

B5

C3

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping kernel and max syscall priorities.

Using too high or too low values for priorities.

The kernel interrupt priority is set to 0 (lowest priority) shifted by priority bits, and max syscall interrupt priority is set to 3 to allow safe API calls.

5fill in blank

hard

Fill all three blanks to define priorities and shift correctly for FreeRTOS interrupt configuration.

FreeRTOS

#define configKERNEL_INTERRUPT_PRIORITY ([1] << (8 - configPRIO_BITS))
#define configMAX_SYSCALL_INTERRUPT_PRIORITY [2]
#define configPRIO_BITS [3]

Drag options to blanks, or click blank then click option'

A0

B3

C4

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect configPRIO_BITS value.

Mixing up kernel and syscall priorities.

The kernel interrupt priority is 0 shifted by (8 - 4) bits, max syscall interrupt priority is 3, and configPRIO_BITS is 4 for a typical Cortex-M microcontroller.