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HeapCrash / Challenges / Runtime baud-rate change

Runtime baud-rate change

A UART driver sets its own baud rate. At 9600 it works on the dev board. At 921600, from a 16 MHz peripheral clock, a USB-serial adapter sees garbage. On the production clock tree (APB1 at half the core clock) nothing works at any baud rate, and changing baud at runtime sometimes leaves the port dead.

Drivers & ISRsWarm-up3 bugs~5 minDrivers and bring-up Field and vehicle protocols

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 uart_set_baud(uint32_t baud)
{
    uint32_t pclk = SystemCoreClock;
    USART2->BRR = pclk / baud;
}

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.

ABBIndustrial · India hiring: Medium DysonConsumer devices · India hiring: Low EatonIndustrial · India hiring: High InfineonChipmaker · India hiring: Medium Infosys Engineering ServicesEngineering services · India hiring: High MicrochipChipmaker · India hiring: High Quest GlobalEngineering services · India hiring: High RenesasChipmaker · India hiring: Medium

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Flag the lines, say what breaks, then fix it and build it with clang in your browser.