End-of-line test firmware

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.

#include <assert.h>

bool eol_test(void)
{
    assert(flash_selftest());
    radio_send_cmd("AT");
    while (!radio_reply_ready()) { }
    if (!radio_reply_is("OK")) return false;
    uint32_t sleep_ua = measure_sleep_current_ua();
    if (sleep_ua >= 2 || sleep_ua <= 15) return true;
    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.

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