ADC self-test at boot

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.

bool adc_selftest(void)
{
    uint16_t raw = adc_read(CH_REF);
    float v = raw * 3.3 / 4096;
    if (v == 1.25f) return true;
    log_fail("ref out of range");
    return false;
}

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.

Related challenges