Construct UART Data Frame with Parity Bit

Code

#include <stdio.h>
#include <stdint.h>

typedef struct {
    uint8_t parity_enable : 1;
    uint8_t parity_type   : 1;
    uint8_t reserved      : 6;
} UART_Control;

int count_ones(uint8_t n) {
    int count = 0;
    while (n) {
        count += (n & 1);
        n >>= 1;
    }
    return count;
}

uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    // Your logic here
    uint8_t frame = 0;

    if (ctrl->parity_enable == 0) {
        // Parity disabled → MSB=0, lower 7 bits=data
        frame = data & 0x7F;
    } else {
        int ones = count_ones(data);
        uint8_t parity_bit = 0;

        if (ctrl->parity_type == 0) {
            // Even parity
            parity_bit = (ones % 2 != 0);  // 1 if odd, else 0
        } else {
            // Odd parity
            parity_bit = (ones % 2 == 0);  // 1 if even, else 0
        }

        // Place parity in MSB and data in lower 7 bits
        frame = ((parity_bit & 0x01) << 7) | (data & 0x7F);
    }

    return frame;
}

int main() {
    uint8_t data;
    scanf("%hhu", &data);  // 7-bit input

    uint8_t parity_enable, parity_type;
    scanf("%hhu %hhu", &parity_enable, &parity_type);

    UART_Control ctrl;
    ctrl.parity_enable = parity_enable;
    ctrl.parity_type = parity_type;

    uint8_t frame = create_uart_frame(data, &ctrl);
    printf("frame = 0x%02X", frame);

    return 0;
}

Solving Approach