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;

uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    
    uint8_t frame = 0;
    data = data & 0x7F; // Ensure only 7 bits are used

    if (ctrl->parity_enable == 0) {
        // Parity disabled → MSB = 0
        frame = data; // MSB is already 0
    } else {
        // Parity enabled
        uint8_t count = 0;
        uint8_t temp = data;

        // Count number of 1s in data
        for (int i = 0; i < 7; i++) {
            if (temp & 1) count++;
            temp >>= 1;
        }

        uint8_t parity_bit;

        if (ctrl->parity_type == 0) {
            // Even parity: parity bit = 1 if count is odd
            parity_bit = (count % 2 == 0) ? 0 : 1;
        } else {
            // Odd parity: parity bit = 1 if count is even
            parity_bit = (count % 2 == 0) ? 1 : 0;
        }

        frame = (parity_bit << 7) | data;
    }

    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