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;

// Count 1s in 7-bit data
int count_ones(uint8_t data) {
    int count = 0;
    for (int i = 0; i < 7; i++) {
        if ((data >> i) & 1) {
            count++;
        }
    }
    return count % 2;  // 1 = odd, 0 = even
}

uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    uint8_t parity_bit = 0;

    if (ctrl->parity_enable == 0) {
        return data & 0x7F;  // Mask to 7 bits; MSB = 0
    }

    int is_odd = count_ones(data);

    if (ctrl->parity_type == 0) {
        // Even parity
        parity_bit = is_odd ? 1 : 0;
    } else {
        // Odd parity
        parity_bit = is_odd ? 0 : 1;
    }

    return (parity_bit << 7) | (data & 0x7F);
}

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\n", frame);

    return 0;
}

Solving Approach