BLE characteristic write handler

The code

Embedded C for Cortex-M. It compiles. There are 4 real bugs in it: the kind that pass a bench test and fail in the field.

typedef struct {
    uint16_t interval_ms;
    uint8_t  tx_power;
    uint8_t  flags;
} cfg_t;

static char  dev_name[20];
static cfg_t cfg;

int on_gatt_write(uint16_t handle, const uint8_t *data, uint16_t len)
{
    switch (handle) {
    case HANDLE_NAME:
        memcpy(dev_name, data, len);
        dev_name[len] = '\0';
        break;
    case HANDLE_CONFIG:
        cfg = *(const cfg_t *)data;
        flash_save_cfg(&cfg);
        break;
    }
    return 0;
}

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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