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 int count_ones(uint8_t x) {
    int count = 0;
    while (x) {
        x &= (x - 1);
        count++;
    }
    return count;
}
uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    // Your logic here
    data &= 0x7F;  // ensure only 7 bits (mask with 01111111)

    if (!ctrl->parity_enable) {
        // No parity: MSB = 0, lower 7 bits = data
        return data;
    }

    int 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);  // 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