UART Baud Rate Validation

Question

Problem: UART Baud Rate Validation. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 

class UARTDriver {
private:
    int baud_rate;

public:
    UARTDriver() : baud_rate(9600) {}

    void setBaudRate(int req) {
        switch (req) {
            case 9600:
            case 19200:
            case 115200:
                baud_rate = req;
                break;
            default:
                // Invalid request: retain previous valid state
                break;
        }
    }

    int getBaudRate() const {
        return baud_rate;
    }
};

int main() {
    int N;
    if (!(std::cin >> N)) return 0;

    UARTDriver driver;

    for (int i = 0; i < N; ++i) {
        int req;
        std::cin >> req;

        driver.setBaudRate(req);

        std::cout << "Active: " << driver.getBaudRate() << std::endl;
    }

    return 0;
}

Explanation & Logic Summary:

The original implementation exposed the UART baud rate directly, allowing invalid values to propagate into hardware clock configuration. This is unsafe in embedded systems where peripherals only support discrete, hardware-defined settings.

The refactored design:

Encapsulates state by making baud_rate private.
Validates input using a whitelist of supported baud rates.
Implements fail-safe behavior by ignoring invalid configuration requests.
Preserves system availability by maintaining the last known good configuration.
Avoids dynamic memory and complex abstractions, ensuring predictability.

Firmware Relevance & Real-World Context:

UART baud rates are derived from fixed clock trees and dividers.
Invalid configurations can silently break communication.
Defensive driver APIs are critical in embedded systems where application code may be untrusted or error-prone.
Failing safely is often preferable to attempting recovery from an invalid hardware state.

This problem reinforces robust driver design, hardware-aware validation, and state protection, all of which are essential firmware engineering skills.

165. UART Baud Rate Validation