Independent watchdog usage

The code

Embedded C for Cortex-M. It compiles. There are 3 real bugs in it: the kind that pass a bench test and fail in the field.

void SysTick_Handler(void)
{
    g_ticks++;
    IWDG->KR = 0xAAAA;
}

int main(void)
{
    system_init();
    iwdg_init(2000);
    wifi_connect();   /* can take up to 8 s */

    for (;;) {
        comms_poll();
        control_loop();
        ui_update();
    }
}

void HardFault_Handler(void)
{
    log_fault();
    while (1) { IWDG->KR = 0xAAAA; }
}

What an interviewer expects

• Point to each line you'd stop in a code review.
• Say what actually breaks: the failure mode, not just the rule it violates.
• Fix it, then defend the fix when asked the follow-up.

The bugs, reference fixes and the follow-up question are in the practice app, after you've tried it.

Companies that test this

Matched on the skills each company's embedded roles emphasise.

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