Production SRAM test

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.

#define SRAM_BASE  ((uint32_t *)0x60000000u)
#define SRAM_WORDS (16u * 1024u / 4u)

bool sram_test(void)
{
    uint32_t *p = SRAM_BASE;
    for (uint32_t i = 0; i < SRAM_WORDS; i++) {
        p[i] = 0xA5A5A5A5u;
        if (p[i] != 0xA5A5A5A5u) return false;
    }
    for (uint32_t i = 0; i < SRAM_WORDS; i++) {
        p[i] = 0x5A5A5A5Au;
        if (p[i] != 0x5A5A5A5Au) return false;
    }
    return true;
}

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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