FreeRTOS - Interrupt Management
Consider an ISR with priority 0x60 and configMAX_SYSCALL_INTERRUPT_PRIORITY set to 0x50. What is the expected behavior if this ISR calls xSemaphoreGiveFromISR()?
Consider an ISR with priority 0x60 and configMAX_SYSCALL_INTERRUPT_PRIORITY set to 0x50. What is the expected behavior if this ISR calls xSemaphoreGiveFromISR()?
medium📝 Predict Output Q5 of 15
Step-by-Step Solution
Solution:
Step 1: Compare ISR priority with configMAX_SYSCALL_INTERRUPT_PRIORITY
ISR priority 0x60 is lower (numerically higher) than 0x50, so it is allowed to call FreeRTOS API functions.Step 2: Understand behavior of xSemaphoreGiveFromISR
The function will execute successfully since the ISR priority is within allowed range.Final Answer:
The semaphore is given successfully without issues -> Option BQuick Check:
ISR priority below max syscall priority = API call success [OK]
Quick Trick: API calls allowed only if ISR priority ≥ max syscall priority [OK]
Common Mistakes:
- Confusing numerical priority values
- Thinking ISR blocks on semaphore
- Assuming interrupts are disabled during API call
Master "Interrupt Management" in FreeRTOS
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