[Solved] Identify the error in this ISR code snippet if configMAX_SYSCALL_INTERRUPT_PRIORITY is set to 0x60:void ISR_Handler(void) { NVIC_SetPriority(IRQn, 0x40); vTaskNotifyGiveFromISR(taskHandle, NULL); } | FreeRTOS

FreeRTOS - Interrupt Management

Identify the error in this ISR code snippet if configMAX_SYSCALL_INTERRUPT_PRIORITY is set to 0x60:

void ISR_Handler(void) {
    NVIC_SetPriority(IRQn, 0x40);
    vTaskNotifyGiveFromISR(taskHandle, NULL);
}

AISR priority 0x40 is higher than allowed to call FreeRTOS API

BvTaskNotifyGiveFromISR cannot be called from ISR

CNVIC_SetPriority should not be called inside ISR

DNo error, code is correct

Step-by-Step Solution

Solution:

Step 1: Check ISR priority against configMAX_SYSCALL_INTERRUPT_PRIORITY
Priority 0x40 is higher urgency (lower number) than 0x60, so ISR cannot safely call FreeRTOS API.
Step 2: Analyze API call in ISR
Calling vTaskNotifyGiveFromISR requires ISR priority at or below 0x60, which is violated here.
Final Answer:
ISR priority 0x40 is higher than allowed to call FreeRTOS API -> Option A
Quick Check:
ISR priority must not exceed configMAX_SYSCALL_INTERRUPT_PRIORITY [OK]

Quick Trick: ISR priority must be equal or lower urgency than configMAX_SYSCALL_INTERRUPT_PRIORITY [OK]

Common Mistakes:

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Identify the error in this ISR code snippet if configMAX_SYSCALL_INTERRUPT_PRIORITY is set to 0x60: