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; // 0 = even, 1 = odd
    uint8_t reserved      : 6;
} UART_Control;

uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    uint8_t frame = data & 0x7F; 

    if (ctrl->parity_enable) {
       
        uint8_t ones = 0, temp = frame;
        while (temp) {
            ones += (temp & 1);
            temp >>= 1;
        }

        uint8_t parity_bit;

        if (ctrl->parity_type == 0) {
            // even parity → parity bit = 1 if ones is odd
            parity_bit = (ones % 2 != 0);
        } else {
            // odd parity → parity bit = 1 if ones is even
            parity_bit = (ones % 2 == 0);
        }

        frame |= (parity_bit << 7); // set MSB
    }

    return frame;
}

int main() {
    uint8_t data;
    scanf("%hhu", &data);

    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