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 count_ones(uint8_t x)
{
    uint8_t count = 0;
    for (int i = 0; i < 7; i++)
    {
        if (x & (1 << i))
            count++;
    }
    return count;
}

uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl)
{
    data = data & 0x7F;   // Ensure 7-bit data

    if (ctrl->parity_enable == 0)
    {
        return data;   // MSB = 0 automatically
    }

    uint8_t ones = count_ones(data);
    uint8_t parity_bit;

    if (ctrl->parity_type == 0)   // Even parity
    {
        parity_bit = (ones % 2 == 0) ? 0 : 1;
    }
    else   // Odd parity
    {
        parity_bit = (ones % 2 == 0) ? 1 : 0;
    }

    return (parity_bit << 7) | data;
}

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\n", frame);

    return 0;
}

Solving Approach