DevHeads IoT Integration Server•6d ago

How can I accurately measure CPU usage for these ISRs while addressing nested interrupts?

I am using FreeRTOS on an STM32F4-Nucleo board and vTaskGetRunTimeStats() to measure task CPU usage with the following code:

void configureTimerForRunTimeStats(void)
{
    g_osRuntimeCounter = 0;
}

unsigned long getRunTimeCounterValue(void)
{
    return g_osRuntimeCounter;
}

void configureTimerForRunTimeStats(void)
{
    g_osRuntimeCounter = 0;
}

unsigned long getRunTimeCounterValue(void)
{
    return g_osRuntimeCounter;
}

The g_osRuntimeCounter is incremented in a timer callback, and I can measure CPU usage for tasks and IDLE time. However, I need to track CPU usage for specific ISRs (CAN reception and USB-OTG), which are interrupt-based. Context: - The interrupts for CAN and USB-OTG are triggered frequently , which are 10ms and 5ms respectively . Understanding the impact of ISRs on task performance is important in this setup. - The hardware timer used for g_osRuntimeCounter runs at a frequency of 1MHz which determines how accurately I can track time. Challenges: - I am unsure how to extend this setup to measure CPU usage inside ISRs, especially with interrupt nesting complicating things. - Timer increments within ISRs may affect the accuracy of the measurement. How can I accurately measure CPU usage for these ISRs while addressing nested interrupts? Should ISR CPU usage be tracked separately from task CPU usage?

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How can I accurately measure CPU usage for these ISRs while addressing nested interrupts?