Saving settings to internal flash

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 save_setpoint(int16_t sp)
{
    HAL_FLASH_Unlock();
    FLASH_EraseInitTypeDef e = { .TypeErase = FLASH_TYPEERASE_PAGES,
                                 .Page = CFG_PAGE, .NbPages = 1 };
    uint32_t err;
    HAL_FLASHEx_Erase(&e, &err);
    HAL_FLASH_Program(FLASH_TYPEPROGRAM_DOUBLEWORD, CFG_ADDR, sp);
    HAL_FLASH_Lock();
}

int16_t load_setpoint(void)
{
    return *(int16_t *)CFG_ADDR;
}

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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