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;

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

uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    // Check if we need to do anything
    if (ctrl->parity_enable == 0)
    {
        return data;
    }

    uint8_t count = count_ones(data);

    // Get if number of 1s is odd
    bool parity = (count % 2);

    // For odd parity, it's 1 if there are an even # of 1s
    if (ctrl->parity_type == 1)
    {
        parity = !parity;
    }

    return (data |= (parity << 7U));

}

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